Dear All I’m not impressed. We have asked a simple question; we got a very complex answer. Please go back to my lecture.
Wee Leng Gan
2 years ago
Damage induced by complement non fixing DSA.
Recruited inflammatory through Fc receptor and induced antibody mediated rejection.
Direct endothelial injury through VGEF activation.
AMAL Anan
2 years ago
The types of DSA either complement fixing or non fixing .
Non fixing one join with neutrophil through fc portion lead to apoptosis through inflammatory cells and cytokines
And activation of endothelium leads to VGEF proliferation and transplant glomerulopathy
Alyaa Ali
2 years ago
Even in absence of complement activation, some DSAs can cause graft damage through antibody dependent cellular cytotoxicity. The innate immune cells, including neutrophils, macrophages, and natural killer cells, can bind to Fc fragments of DSAs, trigger degranulation, and release lytic enzymes, which cause tissue injury and cell death. This process can mediate smoldering damages to the endothelial cells and is proposed as an important pathogenesis in subclinical and chronic antibody-mediated rejection phenotypes .
Furthermore, DSAs can cause graft injury by direct activation of endothelial proliferation through increasing vascular endothelial growth factor production, upregulating fibroblast growth factor receptor, and increasing its ligand binding as well as other signaling pathways for cellular recruitment . This pathogenesis may contribute to transplant glomerulopathy and vasculopathy that feature vascular intima thickness with smooth muscle cell invasion.
Assafi Mohammed
2 years ago
the mechanism of the damage induced by complement non-fixing DSA
There are number of ways whereby antibodies interact with renal graft endothelium:
1. Complement activation by complement fixing DSA
2. ADCC : a non-fixing DSA binds to transplant endothelium with it’s FC portion, and interact with FC receptor of a leucocyte (NKC) with resultant apoptosis and release of cytokines that recruit further inflammatory cells and subsequent microvascular inflammation and tissue damage.
3. Endothelial Cell dysfunction: non-fixing DSA bind to graft endothelium and after signaling cascades promoting cellular proliferation and enhancement of monocyte’s binding to the endothelium with contribution to intimal proliferation and fibrosis.
4. Accommodation: DSA bind to the renal graft endothelium without evidence of injury. The phenomenon is not well understood.
Ahmed Fouad Omar
2 years ago
What is the mechanism of the damage induced by complement non-fixing DSA?o DSAs can cause graft injury by fixing complement and activation of the complement cascade. However, non-complement fixing DSAs can also cause graft damage
o Non complement fixing DSAs are usually de novo directed against class 2 HLA antigens and cause chronic , slow, subclinical rejection and less severe form of graft damage with poor response of treatment.
Mechanism of the damage induced by complement non-fixing DSA:
A. Antibody dependent cell mediated cytotoxicity( ADCC):
It results from binding of Fc receptor of the DSAs with innate immune cells like NK cells, neutrophils, macrophage, causing degranulation, cellular injury and death.
B. Direct endothelial activation:
DSA directly binds to the endothelium leading to VEGF mediated proliferation and FGF receptor up regulation, both results in chronic vasculopathy and transplant glomerulopathy
References:
1. Rubin Zhang. Donor-Specific Antibodies in Kidney Transplant Recipients.
CJASN January, 2018
2. Handbook of kidney transplantation 6th edition
Balaji Kirushnan
2 years ago
DSA can be complement fixing and complement non fixing…Complement fixing DSA cause antigen antibody interaction and cause graft injury…ABMR can be caused due to non complement fixing DSA also
The primary mechanism of action are
Antibody dependent cellular cytotoxicity – The Fc receptor of the DSA of class II HLA gets bound to the cells of the innate immunity namely the neutrophils, macrophages, NK cells which inturn lead to lysis and degranulation of cells which leads to cell death
Direct stimulation of endothelial cells: The Fc receptor of DSA class II bind to the endothelial cells and cause direct activation and involvement of the sub endothelial matrix and fibroblast recruitment. This inturn leads to increased VEGF and FGF causing fibrosis
Non complement fixing DSA present in the late period after transplantation. They are usually due to de novo DSA against HLA class II namely IgG2 and IgG4. they cause C4d negative ABMR. They cause very slow graft dysfunction which are resistant to standard protocol of treatment. They are mainly responsible for cases of chronic transplant glomerulopathy..
Mahmoud Hamada
2 years ago
Studies have proposed that complement-fixing IgG DSAs are associated with less rates of graft survival compared to non-complement-fixing DSAs, although the latter still portends a worse outcome when compared to recipients with negative DSA titre.
Abdullah Raoof
2 years ago
C1q positive and c1q negative types of DSA may suggest two different process causing CABMR.
C1q is the complement classic pathway’s component , the ability of DSA to bind C1q means its ability to activate the complement system which end to form membrane attack complex formation and subsequent lysis of renal endothelial cells, which lead relatively quickly to graft loss.
In non-complement state, C1q− dnDSAs could cause long-term graft loss independently of complement activation by inducing persistent microcirculation inflammation and antibody-dependent cell cytotoxicity or by direct activation of endothelial cell survival and proliferation.
Somes tudies report that the mechanism of injury in (CABMR), is that DSAs mediate injury by non–complement-mediated path ways or through direct interaction with endothelial cell targets with consequent activation of endothelial cell proliferation.
Cornell et al, in their study Showed that patient with positive DSA develop evidence of CABMR and transplant glomerulopathy (TG) even when complement pathway is inhibited by eculizumab .
Antibody binding to endothelium and will lead to cellular activation involving complement-dependent and –independent pathways leads to the recruitment of natural killer (NK) cells, polymorphonuclear neutrophils and macrophages, which participate in capillaritis and eventual tissue injury. The morphologic nature of endothelial cell injury in acute ABMR demonstrates platelet aggregation, thrombotic microangiopathy (TMA) and neutrophilic accumulation, resulting in an early pattern of cellular necrosis and a relatively rapid decline in allograft function. Chronic ABMR results from a repetitive pattern of chronic thrombotic events and inflammatory changes, which result in cellular injury and repair .
Sis et al report increased numbers of intraglomerular CD56+ natural killer (NK) cells in four of six cases of CAMR. This , other data point to a role for NK cells in CAMR, including increased levels of NK-cell-specific transcripts8 and experimental studies in mice which show that CAMR is dependent on NK cells and not complement fixation.
One report mention that there is evidence of at least three independent mechanisms of injury in CAMR:
1. classic complement fixation, as shown by the beneficial effects of anti-C5 therapy in antibody-mediated rejection in presensitized patients.
2. antibody-mediated rejection mediated by NK cells, independent of complement,
3. endothelial activation by antibody alone, best shown in endothelial cell cultures.
These mechanisms are each may has its own pathological signature in the biopsy, including C4d deposition, deposition of NK cells and markers of endothelial activation. Identification of specific mechanisms of injury in CAMR will help to determine the specific therapy. In addition to strategies to reduce circulating DSAs, complement-dependent CAMR could be addressed with complement inhibitor therapy, whereas Fc-receptor-dependent and NK-cell-dependent CAMR might require cell-directed or Fc inhibitor strategies.
Refrences :
1. Djamali A, Kaufman DB, Ellis TM, Zhong W, Matas A, Samaniego M: Diagnosis and management of antibody-mediated rejection: Current status and novel approaches. 14: 255–271, 2014 Am J Transplant.
2. Farkash EA, Colvin RB: Diagnostic challenges in chronic antibodymediated rejection. Nat Rev Nephrol 8: 255–257, 2012
3.Gwendaline Guidicelli et al , Non-Complement–Binding De Novo Donor-Specific Anti-HLA Antibodies and Kidney Allograft Survival, J Am Soc Nephrol. 2016 Feb; 27(2): 615–625,2015 Jun 5. doi: 10.1681/ASN.
Ramy Elshahat
2 years ago
as shown in the attached figure
antibodies cause destruction through 2 main mechanisms
complement-mediated
non-complement mediated
noncomplement mediated is caused by 2 main pathways
cellular cytotoxicity: binding of the innate immune cells such as neutrophils, macrophages, and NK cells to FC fragment of antibodies, causes degranulation, the release of lytic enzymes, and cell death.
Direct activation of endothelial proliferation by ↑ VEGF, increasing FGF receptors resulting in vascular intima thickness which finally leads to chronic vasculopathy and transplant glomerulopathy.
Ahmed Omran
3 years ago
Graft injury due to DSA occurs with or without complement fixation.
In case of absence of complement fixation, de novo type DSA against HLA class II lead to subclinical and chronic rejection. Cellular injury results from binding of Fc receptor of DSA with macrophages, neutrophils and ,NK cells leading to degranulation and cellular injury; AB dependent cell mediated cytotoxicity. Oher mechanism through binding of DSA to endothelial cells leading to activation with VEGF mediated proliferation in addition to upregulation of FGF receptor leading to transplant glomerulopathy
Dalia Eltahir
3 years ago
1) Antibody dependent cellular cytotoxicity: Binding of innate immune cell such as neutrophil, macrophages and NK cells to FC fragment of donor specific antibodies, causes degranulation, release of lytic enzymes and cell death and sub-clinical decline of graft function not responding to treatment due to late chronic microvascular endothelial injuries lead to late AMR and chronic active AMR .Unlike complement fixing occur early and more sever . 2) Direct activation of endothelial proliferation by ↑ VEGF, increasing FGF receptors and its ligand binding resulting in TG and vascular intima thickness.This pathogenesis lead to chronic vasculopathy and transplant glomerulopathy .
MICHAEL Farag
3 years ago
complement independent antibodies induced cellular cytotoxicity and direct endothelial activation and proliferation through antibody-dependent cellular cytotoxicity. The innate immune cells recruitment including neutrophils, macrophages, and natural killer cells, and binding to Fc fragments of DSAs and trigger degranulation, release lytic enzymes, which cause tissue injury and cell death. usually due to denovo DSA class11 IgG subclass 4 activation which lead to subclinical progressive decline of graft function with poor response to treatment due to late chronic microvascular endothelial injuries and chronic vasculopathy the AMR phenotypes include late acute AMR, chronic active AMR, chronic transplant glomerulopathy.
Mohamed Essmat
3 years ago
Complement non-fixing DSA recruit NK cells, macrophages, and neutrophils through Fc receptors and lead to antibody dependent cellular toxicity that cause tissue injury, cellular recruitment and endothelial proliferation leading to acute ABMR with negative C4d deposit in PTC as well as chronic ABMR and eventual graft loss
nawaf yehia
3 years ago
Complement non-fixing DSA are usually of the IgG4 subclass or less commonly IgG2 ( which the latter might weakly bind complement ) , they are commonly targeting class 2 HLA on graft endothelium and can induce cell damage by the following mechanisms :
1- Ab dependant cellular cytotoxicity , by recuitinmg immune cells namely neutrophils , macrophages & NK cells that by degranulation and release of their lytic enzymes cause cell damage
2- direct endothelial cell activation and proliferation resulting in vasculopathy
in general it tends to occur later than the complement binding type , more associated with chronic changes and subclinical presentation and thereby slower graft loss
Jamila Elamouri
3 years ago
1- Non-complement fixing DSAs target the HLA class 2 on the endothelial cells. so recruiting innate immune cells that include NK cells, macrophages, and neutrophils by binding Fc receptors leads to antibody-dependent cellular toxicity.
2- Non-complement fixing DSAs have direct stimulation effects that cause tissue injury, cellular recruitment, and endothelial proliferation
manal jamid
3 years ago
– IgG has several subclasses (IgG1, -2, -3, and -4), and they have various abilities to activate complement and recruit effector cells through the Fc receptor. Although IgG2 can activate complement weakly, IgG4 does not activate complement at all, but both can recruit effector cells through the Fc receptor. IgG4 is also considered as a biomarker of matured alloresponse and associated with advanced stage of rejection. Lefaucheur et al. recently studied 125 patients with DSAs detected in the first year after kidney transplants: subclinical antibody-mediated rejection was driven by IgG4 iDSA. IgG4 iDSA was associated with later graft injury with increased transplant glomerulopathy and interstitial fibrosis/tubular atrophy. IgG4 iDSA–associated subacute and chronic phenotypes of antibody-mediated rejection
REF: 1. Donor-Specific Antibodies in Kidney Transplant RecipientsRubin Zhang CJASN January 2018, 13 (1) 182-192; DOI: https://doi.org/10.2215/CJN.00700117
Akram Abdullah
3 years ago
. Antibody-mediated rejection affects the renal allograft and leads to graft dysfunction & graft loss by 2 mechanisms, complement-dependent cytotoxicity ( c4d positive ) & non-complement-dependent cytotoxicity (c4d negative ), the latter has 2 pathways to affect the renal allograft involving antibody-mediated cellular cytotoxicity and direct endothelial activation with proliferation. The mechanism of damage induced by complement non-fixing DSA includes: 1) Antibody dependent cellular cytotoxicity: In this, the Fc receptor of DSA is bound by the neutrophils, macrophages and (NK) cells leading to degranulation and lytic enzyme release causing tissue injury and cell death. (slow process, leading to subclinical & chronic AMR) 2) Direct stimulation of endothelial cell: the endothelial cells are directly activated and proliferate due to increased (VEGF), upregulating (FGF) receptors, It leads to vasculopathy (increased vascular intime thickness with smooth muscle invasion) and transplant glomerulopathy.
Heba Wagdy
3 years ago
Complement non binding DSA cause antibody mediated rejection activation of NK cells, macrophages and neutrophils through Fc fragment causing antibody dependent cellular toxicity.
The other mechanism through pleotropic effect and direct stimulation causing tissue damage, cellular recruitment and endothelial proliferation.
Complement non fixing DSA are usually class II and involve IgG2 and IgG4 subclasses.
leads to subclinical, chronic rejection with negative C4d deposition, transplant glomerulopathy and vasculopathy.
usually associated with slow graft dysfunction and tends to be persistent and less responsive to treatment with late graft loss.
Zhang R. Donor-specific antibodies in kidney transplant recipients. Clinical Journal of the American Society of Nephrology. 2018 Jan 6;13(1):182-92.
Theepa Mariamutu
3 years ago
What is the mechanism of the damage induced by complement non fixing DSA
Complement fixing DSA
Targets class 1 HLA on endothelial cells, activate the classical complement cascade and deliver the complement dependent cytotoxicity in Acute ABMR
Theoretically- higher tiger of DSA has been correlated with complement binding capability and more severe tissue injury – sufficient amount of IgG molecules that can bind to antigens close together to form hexametric complexes that can activate complement
Associated with significant higher risk of ABMR, severe tissue injury and graft loss
Detected at 1 year after KT or ABMR was an independent factor of graft loss
Increased risk of graft loss by 4.78-fold
Associated with ABMR with more severe graft injuries that included more extensive inflammation, microvasculitis, endarteritis,transplant glomerulooathy and C4d deposits.
Complement non-fixing DSA
Recruit innate immune cells (NK cells, macrophages, and neutrophils) through Fc receptors and lead to antibody dependent cellular toxicity
Have direct stimulation and pleotrophic effects that cause tissue injury, cellular recruitment and endothelial proliferation
This mechanism plays a vital role in acute ABMR with negative C4d deposit in PTC as well as chronic ABMR
Led to graft loss in the long term
Reference
Rubin Zhang .Donor-Specific Antibodies in Kidney Transplant Recipients CJASN January 2018, 13 (1) 182-192; DOI: https://doi.org/10.2215/CJN.00700117
Professor Ahmed Halawa
Admin
3 years ago
Dear All, Yes, lead to a subclinical progressive decline of graft function with poor response to treatment due to late chronic microvascular endothelial injuries and chronic vasculopathy the AMR phenotypes include late acute AMR, chronic active AMR, and chronic transplant glomerulopathy. You can tell clearly that non-complement fixing antibodies are also graft damaging, but the phenotypes of damage is different from complement-fixing antibodies, which are severe, and usually happens early.
saja Mohammed
3 years ago
the pathogeneses of antibody-mediated rejection include
1-Dirct complement-dependent cytotoxicity, C1q binding with C4D positive characterized by aggressive type of accelerated acute or hyper-acute AMR with early graft loss usually due to performed DSA with subclass IgG3 and its direct complement dependent effectors cells activations through the FC receptors binding activity in previously sensitized recipient with high PRA% of preformed DSAs which could include both class1 ,class2 DSAs.
2-complement independent antibodies induced cellular cytotoxicity and direct endothelial activation and proliferation through antibody-dependent cellular cytotoxicity. The innate immune cells recruitment including neutrophils, macrophages, and natural killer cells, and binding to Fc fragments of DSAs and trigger degranulation, release lytic enzymes, which cause tissue injury and cell death. usually due to denovo DSA class11 IgG subclass 4 activation which lead to subclinical progressive decline of graft function with poor response to treatment due to late chronic microvascular endothelial injuries and chronic vasculopathy the AMR phenotypes include late acute AMR, chronic active AMR, chronic transplant glomerulopathy.
Risk factors for deno DSA
1-Higher HLA mismatch especially calss11 DQ mismatch.
2- nonadherences to immunosuppression
3-graft inflammation, due to viral infection, previous TCMR, ischemic injuries
Which increased the graft immunogenicity.
References
1-Lefaucheur C, Viglietti D, Bentlejewski C, et al. IgG Donor-Specific Anti-Human HLA Antibody Subclasses and Kidney Allograft Antibody-Mediated Injury. J Am Soc Nephrol. 2016;27(1):293-304.
2-Zhang, Rubin. “Donor-Specific Antibodies in Kidney Transplant Recipients.” Clinical journal of the American Society of Nephrology: CJASN vol. 13,1 (2018): 182-192
Thanks, Saja Yes, lead to a subclinical progressive decline of graft function with poor response to treatment due to late chronic microvascular endothelial injuries and chronic vasculopathy the AMR phenotypes include late acute AMR, chronic active AMR, and chronic transplant glomerulopathy.
Esmat MD
3 years ago
The pathogeneses of antibody-mediated rejection include not only complement-dependent cytotoxicity, but also complement independent pathways of antibody-mediated cellular cytotoxicity and direct endothelial activation and proliferation.
C1q nonbinding donor-specific antibodies correlate with subclinical or chronic antibody-mediated rejection and late graft loss, and non -complement binding IgG4 and igG2 donor-specific antibodies are more correlated with subclinical or chronic antibody mediated rejection and transplant glomerulopathy as well.
Although activation of the complement pathway by binding of DSA to endothelial cell antigens is the main mechanism of graft injury in AMR, even in the absence of complement activation, some DSAs can lead to graft damage through antibody dependent cellular cytotoxicity. Binding of the innate immune cells, consists of neutrophils, macrophages, and natural killer cells, to Fc fragments of DSAs, triggers degranulation, and releases lytic enzymes, which lead to tissue injury and cell death. This silent and gradual process can result in endothelial cell damage and is proposed as an important pathogenesis in subclinical and chronic AMR phenotypes. Another complement independent mechanism is direct stimulation and activation of endothelial proliferation by DSAs with pleotrophic effects through increasing vascular endothelial growth factor production, upregulating fibroblast growth factor receptor, and increasing its ligand binding as well as other signaling pathways for cellular recruitment that ultimately lead to graft injury, and it may contribute to transplant glomerulopathy and vasculopathy, and present as peritubular arteries C4d negative AMR.
Binding of donor-specific antibodies (DSAs) to kidney allograft endothelial cells that does not activate the classic complement Cascade can trigger the recruitment of innate immune effectors, including NK cells. Activated NK cells contribute to microvascular inflammation leading to chronic AMR. Recipient NK cells can also trigger antibody-independent microvascular inflammation by sensing the absence of self HLA class I molecules (“missing self”) on allograft endothelial cells. As a result, the assessment of missing self at the time of diagnosis of chronic AMR identifies patients at higher risk for kidney transplant failure.
However, compared with C1q nonbinding DSAs, C1q binding DSAs are associated with significantly higher risk of antibody-mediated rejection, severe tissue injury, and graft loss.
I can summarise your reply. It gives a less severe and more chronic form of graft damage. Well done
Last edited 3 years ago by Professor Ahmed Halawa
Ahmed Abd El Razek
3 years ago
first mechanism : as C1q is the complement classic pathway’s first protagonist, the ability of DSA to bind C1q in vitro should determine its ability to activate the complement cascade in vivo, before membrane attack complex formation and subsequent lysis of renal endothelial cells, which lead relatively quickly to graft loss.
second mechanism: C1q− dnDSAs could cause long-term graft loss independently of complement activation by inducing persistent microcirculation inflammation and antibody-dependent cell cytotoxicity, or by direct activation of endothelial cell survival and proliferation.
acute antibody-mediated rejection was mainly driven by IgG3 , whereas subclinical antibody mediated rejection was driven by IgG4 .
IgG3 was associated with a shorter time to rejection, increased microcirculation injury, and positive C4d deposits, which indicate the complement-dependent cytotoxicity.
IgG4 was associated with later graft injury with increased transplant glomerulopathy and interstitial fibrosis/tubular atrophy.
Nasrin Esfandiar
3 years ago
There are two mechanisms for injury and damage induced by complement
non-fixing DSA:
1) Antibody dependent cellular cytotoxicity:
Binding of innate immune cell such as neutrophil, macrophages and NK cells to FC fragment of donor specific antibodies, causes degranulation, release of lytic enzymes and cell death and sub clinical and CAMR.
2) Direct activation of endothelial proliferation by ↑ VEGF, increasing FGF receptors and its ligand binding resulting in TG and vascular intima thickness.
Thank you for explaining the mechanisms, but how does it differ in presentation compared to complement-fixing?
Drtalib Salman
3 years ago
Ab mediated rejection by anti HLA which could be FC portion (complement fixing) or non complement (other mechanism ) depend on subclass of anit HLA , titre and affinity of Ab to react with endothelial cell of allograft .
complement independent :
1- HLA promote smooth muscle cell proliferation through focal adhesion kinase which lead to neointimal change especially in chronic Ab mediated rejection and recent evidence implicate role of mellatoproteinase and neutral sphingomyelinase in smooth cell proliferation .
2- HLA crosslinking activated Rho kinase ,myocin light chin kinase in calcium independent manner which stimulate stress fiber formation .
3-HLA cross linking lead to macrophage recruitment to allograft and trigger two type of activation type one (rapid and transient induction of adhesion molecules and type 2 (lead to chemokine and adhesion molecule).
Dear All
Most of you gave detailed information about the mechanism of non complement fixing antibodies on the endothelial graft cells few gave a simple comprehensive answer which will be useful if you add the following scheme which helps you as practicing nephrologists:
1. Possible eitiology
2HLA class
3. MFI ,cross match
4.Time of appearance
5.which Effector cells ( Innate immunity)
6.Time of start of graft dysfunction ,pathology
7.course and response to treatment
By addressing these point a diagnosis and management will be amenable.
Thank you for explaining the mechanisms, but how does it differ in presentation compared to complement-fixing?
Reem Younis
3 years ago
–In absence of complement activation, some DSAs can cause graft damage through antibody-dependent cellular cytotoxicity. The innate immune cells, including neutrophils, macrophages, and natural killer cells, can bind to Fc fragments of DSAs, trigger degranulation, and release lytic enzymes, which cause tissue injury and cell death. This process can mediate smoldering damages to the endothelial cells and is proposed as an important pathogenesis in subclinical and chronic antibody-mediated rejection phenotypes .
-Furthermore, DSAs can cause graft injury by direct activation of endothelial proliferation through increasing vascular endothelial growth factor production, upregulating fibroblast growth factor receptor, and increasing its ligand binding as well as other signaling pathways for cellular recruitment . This pathogenesis may contribute to transplant glomerulopathy and vasculopathy that feature vascular intima thickness with smooth muscle cell invasion. The latter two complement-independent mechanisms can explain the clinical phenotypes of antibody-mediated rejection with negative C4d staining in peritubular capillaries. Reference:
-Rubin Zhang .Donor-Specific Antibodies in Kidney Transplant Recipients
CJASN January 2018, 13 (1) 182-192; DOI: https://doi.org/10.2215/CJN.00700117
What is the mechanism of the damage induced by complement non-fixing DSA?Non- HLA antibodies against surface may fixing complement or mediated ADCC depend on signaling capacity and biological function of the ligand as with HLA1 molecules. For example angiotensin 11 recptor AT1 antibodies are well established against which promote HTN and contribute to renal allograft injury.
antibodies upregulates adhesion molcules and cytokines on endothelial cells but when the target is unkonown the precise mechanism remain elusive to date ,little has been studied on the action of non HLA antibodies during humoral alloimmune response.
example of non-HLA antibodies MICA and MICB that function as ligands for the NK cells receptors, these antibodies associated with chronic rejection .
non HLA antibodies in transplantion can be directed against either polymorphism or non allelic proteins . The development of antibodies against non polymorhoric target may be due to upregularation during inflammation , in response to transplantaion or when protiens are exposed to the immune system during injury , it is thought that intergraft microenviroment or rejection may break humoral tolerance to autoantigens,
non HLA antiendotheialial cell antibodies has increase incidence of failed graft.
References1. Zhang Q, Cecka JM, Gjertson DW, Ge P, Rose ML, Patel JK, et al. HLA and MICA: targets of antibody-mediated rejection in heart transplantation. Transplantation. 2011;91:1153–1158. [PMC free article] [PubMed] [Google Scholar]
2. Cardarelli F, Pascual M, Tolkoff-Rubin N, Delmonico FL, Wong W, Schoenfeld DA, et al. Prevalence and significance of anti-HLA and donor-specific antibodies long-term after renal transplantation. Transpl Int. 2005;18:532–540. [PubMed] [Google Scholar]
3. Everly MJ, Everly JJ, Arend LJ, Brailey P, Susskind B, Govil A, et al. Reducing de novo donor-specific antibody levels during acute rejection diminishes renal allograft loss. Am J Transplant. 2009;9:1063–1071. [PubMed] [Google Scholar.
Thank you for explaining the mechanisms, but how does it differ in presentation compared to complement-fixing?
Shereen Yousef
3 years ago
*The pathogeneses of antibody-mediated rejection includes not only complement-dependent cytotoxicity, but also complement-independent pathways of antibody-mediated cellular cytotoxicity and direct endothelial activation and proliferation.
*C1q nonbinding donor-specific antibodies correlate with subclinical or chronic antibody-mediated rejection and late graft loss.
*in absence of complement activation, some DSAs can cause graft damage through antibody-dependent cellular cytotoxicity.
* innate immune cells, including neutrophils, macrophages, and natural killer cells, can bind to Fc fragments of DSAs, trigger degranulation, and release lytic enzymes, which cause tissue injury and cell death.
*This can mediate damages to the endothelial cells causing subclinical and chronic antibody-mediated rejection.
*DSAs can also cause graft injury by direct activation of endothelial proliferation through increasing vascular endothelial growth factor production, upregulating fibroblast growth factor receptor, and increasing its ligand binding as well as other signaling pathways for cellular recruitment .
* complement-independent mechanisms can explain the clinical phenotypes of antibody-mediated rejection with negative C4d staining in peritubular capillaries.
*HLA antibodies act as agonists to induce intracellular signaling in endothelial and smooth muscle cells.
these effects are independent of the Fc fragment, and may therefore be elicited by any IgG subclass.
*HLA I antibodies promote focal adhesion kinase (FAK)-dependent proliferation and migration of smooth muscle cells, which may contribute to the neointimal changes seen in chronic rejection.
*Recent evidence has also implicated matrix metalloproteinase-2 (MMP2) and neutral sphingomyelinase-2 (nSMase2) in HLA I antibody-induced smooth muscle cell proliferation in vitro and in vivo , which is interesting in clinical observations of increased intragraft expression of MMP2 during AMR .
*addition to early endothelial activation, HLA I antibodies induce late phase adhesion molecules and synthesis of chemoattractants and inflammatory cytokines that promote inflammation.
*HLA I crosslinking activated the transcription factor cAMP response element binding protein (CREB), which lead to increased adhesion molecule and chemokine expression by microvascular endothelium, and monocyte adhesion
*studies found increased synthesis of cytokines and chemokines by endothelial cells from other vascular beds upon exposure to HLA antibodies
with Production of inflammatory mediators by endothelial cell antibodies stimulated with HLA antibodies.
Reference
Rubin Zhang.Donor-Specific Antibodies in Kidney Transplant Recipients. CJASN January 2018, 13 (1) 182-192.
Nicole M Valenzuela, Jeffrey T McNamara, and Elaine F Reed.Antibody-Mediated Graft Injury: Complement-Dependent and Complement-Independent Mechanisms.Curr Opin Organ Transplant. 2014 Feb; 19(1): 33–40.
1-HLA antibodies act as agonists to induce intracellular signaling in endothelial and smooth muscle cells. these effects are independent of the Fc fragment, and may therefore be elicited by any IgG subclass.
2-HLA I antibodies promote focal adhesion kinase (FAK)-dependent proliferation and migration of smooth muscle cells ,which may contribute to the neointimal changes seen in chronic rejection.
3-Recent evidence has also implicated matrix metalloproteinase-2 (MMP2) and neutral sphingomyelinase-2 (nSMase2) in HLA I antibody-induced smooth muscle cell proliferation in vitro and in vivo ,which is interesting in light of clinical observations of increased intragraft expression of MMP2 during AMR .
4-Cell proliferation and migration are dependent upon reorganization of the cytoskeleton with the suggestion that ERK1/2 is a critical regulator of endothelial cytoskeletal changes, migration and motility .
5-macrophages are key immune mediators of graft injury. Endothelial cells actively regulate infiltration of leukocytes from the bloodstream into the tissue.
6-Type 1 endothelial cell activation involves rapid and transient induction of adhesion molecules and chemoattractants, while type 2 activation requires protein synthesis resulting in chemokine and adhesion molecule expression over the course of hours or days.
7-Emerging evidence indicates that HLA crosslinking can trigger both type 1 and type 2 endothelial cell activation, providing some insight into the mechanisms of macrophage recruitment to the allograft during HLA antibody-mediated injury.
8-HLA I crosslinking by antibodies triggers rapid endothelial exocytosis (<30min, type 1 activation) leading to cell surface presentation of the adhesion molecule P-selectin and release of vWF from aortic, venous and microvascular endothelial cells .This induction did not require the Fc portion of the antibody, suggesting that all IgG subclasses can elicit pathogenic effects by direct endothelial cell activation.
9-HLA I antibodies induce late phase adhesion molecules and synthesis of chemoattractants and inflammatory cytokines that promote inflammation.
10- also found increased synthesis of cytokines and chemokines by endothelial cells from other vascular beds upon exposure to HLA antibodies .
Reference:
Antibody-Mediated Graft Injury: Complement-Dependent and Complement-Independent Mechanisms
Nicole M Valenzuela, Jeffrey T McNamara, and Elaine F Reed.
You described the direct effect of the non complement fixing antibodies IGg 2,4 on the endothelial cells
What about the innate immunity cells , is the mechanism different?
Can you correlate the mechanism with the clinical setup
Are there predisposing factors.
innate immune cells, including neutrophils, macrophages, and natural killer cells, can bind to Fc fragments of DSAs, trigger degranulation, and release lytic enzymes, which cause tissue injury and cell death. *This can mediate damages to the endothelial cells causing subclinical and chronic antibody-mediated rejection.
The etiology due to ischemia-reperfusion injury, non-adherence to IS or viral infection
The rejection is chronic late in presentation lead to late AMR or chronic active AMR.
It slowly progressed but eventually lead to graft loss
The mechanism of injury by antibody-mediated cellular toxicity or direct endothelial damage and swelling.
Mahmud Islam
3 years ago
HLA antibodies act as agonists to induce intracellular signalling in endothelial and smooth muscle cells. This is independent of the Fc fragment. Any IgG class may elicit this. FAK (focal adhesion kinase) and MMP-2 (matrix metalloproteinase-2) and nSMase2 (neutral sphingomyelinase) may play role. active MMP2 acts on nSMase to stimulate ceramide, which is itself pro-inflammatory. Class I HLA antibodies promote FKA dependent proliferation and migration of smooth muscles.
In heart transplantation, intracapillary macrophages are an important hallmark of AMR in cardiac allografts.
but how does it differ in presentation compared to complement-fixing?
Dalia Ali
3 years ago
Even in absence of complement activation, some DSAs can cause graft damage through antibody-dependent cellular cytotoxicity. The innate immune cells, including neutrophils, macrophages, and natural killer cells, can bind to Fc fragments of DSAs, trigger degranulation, and release lytic enzymes, which cause tissue injury and cell death. This process can mediate damages to the endothelial cells and have an important role in pathogenesis of subclinical and chronic antibody-mediated rejection phenotypes
Furthermore, DSAs can cause graft injury by direct activation of endothelial proliferation through increasing vascular endothelial growth factor production, upregulating fibroblast growth factor receptor, and increasing its ligand binding as well as other signaling pathways for cellular recruitment
This pathogenesis may contribute to transplant glomerulopathy and vasculopathy that feature vascular intima thickness with smooth muscle cell invasion. The latter two complement-independent mechanisms can explain the clinical phenotypes of antibody-mediated rejection with negative C4d staining in peritubular capillaries.
Reference
Rubin Zhang. Donor-Specific Antibodies in Kidney Transplant Recipients. Clin J Am Soc Nephrol 13: 182–192, 2018. doi: https://doi.org/10.2215/CJN.00700117
Very good concise and clear
Can you relate the mechanism explained to the clinical scenario of the patient along with the work up plan ie possible eitiology
Type of HLA class
Time of formation
Effector cells
Cross match
Time of rejection
Type of rejection
Graft outcome
Response to treatment
Sorry complement non fixing IgG subclasses IgG 2,IgG 4
kumar avijeet
3 years ago
DSA can cause graft injury by both complement fixation and without complement fixation.
DSA can cause graft injury without complement fixation, which are generally denovo variety with dsa against HLA class 2 and cause subclinical and chronic rejection.
A.ADCC-antibody dependant cell mediated cytotoxicity, which is due to binding of Fc receptor of dsa with neutrophils,macrophage, NK cell with degranulation and cellular injury.
B.DIRECT ENDOTHELIAL ACTIVATION-DSA bound to endothelium and directly activates endothelium leading to VEGF mediated proliferation and FGF receptor upregulation, both leading to transplant glomerulopathy.
1. What is the mechanism of the damage induced by complement non-fixing DSA? Antibody mediated rejection, leading cause of graft dysfunction and graft loss post-trasnplant, can be either due to complement dependent cytotoxicity, or due to non-complement dependent pathways involving antibody-mediated cellular cytotoxicity and direct endothelial activation with proliferation.
The mechanism of damage induced by complement non-fixing DSA includes:
1) Antibody dependent cellular cytotoxicity: In this, the Fc receptor of DSAs (against class II HLA) gets bound by the neutrophils, macrophages and CD3-CD16+ natural killer (NK) cells leading to degranulation and lytic enzyme release causing tissue injury and cell death. It is usually a slow process, leading to subclinical and chronic AMR phenotypes.
2) Direct stimulation of endothelial cell: In this, the endothelial cells are directly activated and proliferate due to increased vascular endothelial growth factor (VEGF), upregulating fibroblast growth factor (FGF) receptor, increasing ligand binding and other pathways for leukocyte recruitment further causing tissue injury and endothelial proliferation. It leads to vasculopathy (increased vascular intime thickness with smooth muscle invasion) and transplant glomerulopathy. Complement non-fixing DSA present with C4d negative staining in peritubular capillaries, hence designated C4d negative AMR. These are usually due to class II DSAs, appearing later in post-transplant period, involving IgG subclasses IgG2 and IgG4, present with chronic and subclinical phenotypes having slowly progressing graft dysfunction and late graft loss with poor response to treatment.
References: 1) Zhang R. Donor-Specific Antibodies in Kidney Transplant Recipients. Clin J Am Soc Nephrol. 2018 Jan 6;13(1):182-192. doi: 10.2215/CJN.00700117. Epub 2017 Apr 26. PMID: 28446536; PMCID: PMC5753302. 2) Valenzuela NM, Reed EF. Antibodies in transplantation: the effects of HLA and non-HLA antibody binding and mechanisms of injury. Methods Mol Biol. 2013;1034:41-70. doi: 10.1007/978-1-62703-493-7_2. PMID: 23775730; PMCID: PMC3879955. 3) Valenzuela NM, McNamara JT, Reed EF. Antibody-mediated graft injury: complement-dependent and complement-independent mechanisms. Curr Opin Organ Transplant. 2014 Feb;19(1):33-40. doi: 10.1097/MOT.0000000000000040. PMID: 24316758; PMCID: PMC4080796.
v Mechanism of graft injury in non -complement fixing antibodies:
1. Recruitment of inflammatory cells as neutrophils, macrophages and NK cells that bind to Fc portion of DSA that lead to their degranulation and release of proteolytic enzymes that induce graft damage.
2. Endothelial cell activation and swelling by alloantibodies which leads to microvascular inflammation and stimulation of inflammatory cascade with further recruitment of inflammatory cells.
3. T cell activation (antibody dependent cellular toxicity).
4. Endothelial cell associated transcripts.
v Difference between complement fixing and non fixing antibodies mediated rejection:
ABMR can be considered as the main cause of graft loss ,there are different forms of ABMR that occurs post kidney transplant depending on the time of the rejection,IgG classes and the strength of the antibodies detected all these factors can cause hyperacute,accelerated early acute,and late acute rejection.
Late acute rejection mainly caused by de novo DSA which is also responsible for chronic ABMR and glomerulopathy.
Complement fixing activation is the triggering factor for ABMR it has C4d deposition while non complement fixing activation also responsible for ABMR by subsequent endothelial activation and proliferation leading to inflammation in micro circulation.
Refrence
_Zhang R. at al , Donor Specific Antibodies in Kidney Transplant Recipients. Clin J Am Soc Nephrol. 2018;13(1):182_192.
complement-independent cytotoxicity is through 2 mechanisms:
1. through innate immune cells, including neutrophils, macrophages, and natural killer cells, which bind to Fc fragments of DSAs, triggering degranulation, and release of lytic enzymes, which cause tissue injury and cell death. This results in subclinical and chronic antibody-mediated rejection phenotypes
2. through direct activation of endothelial proliferation through increasing vascular endothelial growth factor production, upregulating fibroblast growth factor receptor, and increasing its ligand binding as well as other signaling pathways for cellular recruitment. This can result in transplant glomerulopathy and vasculopathy that feature vascular intima thickness with smooth muscle cell invasion . How the rejection caused by complement-fixing antibodies differs from complement non-fixing?
C1q binding DSA and Complement binding IgG3 are closely associated with acute AMR, more severe graft injuries, and early graft failure.
C1q nonbinding and non-complement binding IgG4 DSA correlate with subclinical or chronic AMR and late graft loss. The non-complement binding IgG4 DSA are more correlated transplant glomerulopathy.
Zhang R. Donor-Specific Antibodies in Kidney Transplant Recipients. Clin J Am Soc Nephrol. 2018;13(1):182-192. doi:10.2215/CJN.00700117
Yes, gives less severe and looks like a chronic form of graft damage
Nandita Sugumar
3 years ago
C1q binding indicates the clinical relevance of de novo DSA. Complement non fixing DSA can cause long term graft loss independent of complement activation by inducing persistent microvascular inflammation and antibody dependent cell cytotoxicity, or by direct activation of endothelial cell survival and proliferation.
This is in contrast to complement fixing DSA which cause graft loss by activating the complement cascade in Vito , before membrane attack complex formation and leading to subsequent lysis of renal endothelial cells, resulting in graft loss.
Complement non-fixing DSA target HLA II on endothelial cells. Natural killer cells, macrophages and neutrophils are recruited by these DSA through Fc receptors, resulting in antibody dependent cell toxicity. Complement non-fixing DSA also directly stimulate tissue injury, cell recruitment and endothelial proliferation. These 2 mechanisms play a role in
Acute AMR, negative C4d deposit in peritubular capillaries
cAMR
transplant glomerulopathy
vasculopathy
possible immunological damage caused by APC and NK cells.
Reference :
Guidicelli, G., Guerville, F., et al. Non-complement binding de novo donor specific anti – HLA antibodies and kidney allograft survival. JASN February 2016, 27(2) 615-625; DOI: https://doi.org/10.1681/ASN.2014040326
Professor Ahmed Halawa. Applied Transplant immunology; Case Based Discussion (part 2). Fellowship in Clinical Transplantation ASNRT.
This is excellent, Nandita Short, sweet and without jargon.
Mohamed Saad
3 years ago
What is the mechanism of the damage induced by complement non-fixing DSA?Complement nonbinding DSAs target the class 2 HLA on endothelial cells and recruit innate immune cells (NK cells, macrophages, and neutrophils) through Fc receptors and lead to antibody-dependent cellular toxicity.
• In addition, complement nonbinding DSAs have direct stimulation effects that cause tissue injury, cellular recruitment, and endothelial proliferation.
• The latter two mechanisms play an important role in acute AMR with negative C4d deposit in peritubular capillaries as well as cAMR, transplant glomerulopathy, vasculopathy and possible immunological damage caused by APC, antigen-presenting cells; NK, natural killer cells.
References:
1-Applied Transplant Immunology; Case-based Discussion (Part 2) By professor : Ahmed Halawa.
What is the mechanism of the damage induced by complement non-fixing DSA?
# The presence of DSA, either preformed or de novo is biomarker for predicting poor transplant outcomes, including high incidence of ABMR.
*The risk factors for de novo DSA include the following:
(1) high HLA mismatches (especially DQmismatches) (2) inadequate immunosuppression and nonadherence
(3) graft inflammation, such as viral infection, cellular rejection, or ischemia injury, which can increase graft immunogenicity
* De novo DSAs are predominantly directed to donor HLA class 2 mismatches and usually occur during the first year of kidney transplant, but they can appear anytime
** DSA can cause graft injury through 2mechanism:
# Complement fixing antibody cause graft damage through:
binding of DSA to antigen expressed on allograft endothelial cells can activate classic complement pathway, a key pathologic process of acute antibody mediated rejection phenotypes
DSAs are well-known biomarkers of antibody-mediated rejection, and they have been linked to lower graft survival and loss rates in studies.
In addition to complement-dependent cytotoxicity, antibody-mediated rejection can result in direct endothelial activation and proliferation, as well as tissue and cell injuries. Neutrophils, macrophages, and natural killer cells can bind to DSA Fc fragments and trigger degranulation and the release of a lytic enzyme (innate immune response), which can result in tissue and cell injuries as well as direct stimulation of endothelial growth factor secretion and proliferation.
Some DSAs have the potential to produce graft destruction even in the absence of complement activation.
The cytotoxicity of cells that is mediated by antibodies:
The innate immune cells, which include neutrophils, macrophages, and natural killer cells, are responsible for protecting the body from infection.
may attach to Fc segments of DSAs, causing degranulation and the release of lytic enzymes, among other things can induce tissue harm and cell death in a variety of ways
DSAs have the potential to induce graft damage via the stimulation of endothelial proliferation.
boosting the synthesis of vascular endothelial growth factors and upregulating the development of fibroblasts
enhancing the ligand-binding affinity of the factor receptor, as well as additional signalling pathways for the factor.
References: Zhang R. Donor-Specific Antibodies in Kidney Transplant Recipients. Clin J Am Soc Nephrol.
Thank you for explaining the mechanisms, but how does it differ in presentation compared to complement-fixing?
Tahani Ashmaig
3 years ago
▪︎Antibodies to HLA are IgG class
▪︎ IgG occurs as a monomer and can be devided into four subclasses
▪︎ IgG1 and IgG3 are the main activator of the classical Complement PW [1].
▪︎IgG2 and IgG4 antibodies do not fix complement and bind very poorly to activating FcγR.
▪︎ HLA antibodies also act as agonists to induce intracellular signaling in endothelial and smooth muscle cells. Notably, these effects are independent of the Fc fragment, and may therefore be elicited by any IgG subclass.
▪︎Complement non fixing Donor specific HLA antibodies stimulate endothelial cell signaling, including rapid exocytosis of P-selectin and production of chemokines, leading to inflammatory activation and leukocyte recruitment [2].
________________________
Ref:
[1]Mark Pearland. ” Basic and Clinical Immunology “.2nd edition
[2] Nicole M Valenzuela, Jeffrey T McNamara, and Elaine F Reed “Antibody-Mediated Graft Injury: Complement-Dependent and Complement-In dependent Mechanisms”.
Thank you for explaining the mechanisms, but how does it differ in presentation compared to complement-fixing?
Filipe prohaska Batista
3 years ago
Antibody-dependent cellular cytotoxicity
· Mechanism: identification of Fc portion of the AB by the innate immune cells – tissue injury and cell death.
· This mechanism is implicated in subclinical and chronic antibody-mediated rejection phenotypes and c4d negative ABMR 2. . Direct activation of endothelial proliferation
· Increases the production of vascular endothelial growth factor, fibroblast growth factor receptor upregulation, and increases its ligand binding as well as other signaling pathways for cellular recruitment
· This may cause transplant glomerulopathy, vasculopathy, and C4d negative ABMR
Humoral immunity may find different pathways for antibody production, either primarily (autoantibodies) or by exposing donor antigens outside the HLA complex (alloantibodies), inducing antibody-mediated rejection. This response is quite heterogeneous and multifactorial, involving increased or decreased expressions, ischemic injury, and inflammatory state of the allograft.
Angiotensin type 1 receptor (AT1R)
– Triggers apparently vascular lesion refractory to the use of corticosteroids
– Malignant hypertension
– Major vascular rejection
– Usually does not use complement to trigger the lesion
– May trigger acute rejection in the first 4 months or late after 3 years of transplantation
– Appears to be related to recurrent focal and segmental glomerulosclerosis
– When associated with DSA/HLA, the prognosis worsens
– Treatment is based on a combination of plasmapheresis, intravenous immunoglobulin, and losartan
Perlecan
– Important component of vascular endothelium
– Predominant activity in the LG3 subdomain
– LG3 suggests being a regulator of vascular remodeling
– May lead to vascular lesions and synergize with HLA-DSA, similar to what occurs with AT1R antibodies
Collagen
– Expresses metalloproteases that modify collagen and lead to the production of autoantibodies
– In lung transplantation, it is common to trigger bronchiolitis obliterans syndrome
– In kidney transplantation, it is common to cause transplantation glomerulopathy
– Uses the Th17 axis and interleukins can lead to direct graft injury (IL17) or autoantibody production (IL23)
Autoantibody production in transplantation
– Ischaemia reperfusion injury
– Alloimmunity x Autoimmunity
– Extracellular vesicles
– Th17 cells and tertiary lymphoid tissues
All of these paths can occur autoantibody production might occur via several mechanisms, including extracellular vesicles, apoptotic bodies, cross-reactivity between self and foreign antigens, and the interplay between innate and adaptive immunity induced by the Th17 IL 12-17-23 path.
Thank you for explaining the mechanisms, but how does it differ in presentation compared to complement-fixing? Please see above
Sahar elkharraz
3 years ago
HLA antibodies and non-HLA Abs-binding endothelial cells are associated with the activation of complement and non complement system and lead to early AMR.
Complement non fixing DSA igG4 are associated with late graft loss and chronic AMR.
it’s also assessed with transplant glomerulopathy.
Pathogenesis of antibody-mediated rejection include complement-dependent cytotoxicity and complement-independent pathways of antibody-mediated cellular cytotoxicity and direct endothelial activation and proliferation.
Donor-specific anti-endothelial cell Abs detected in the pre-transplant evaluation.
Complements factor C3c, C3d and immunoglobulin G (IgG) deposit on T and B cells are detected on EPCs; it’s can detected by complement-dependent cytotoxicity assay.
References
Zhang R. et al,Donor-Specific Antibodies in Kidney Transplant Recipients. Clin J Am Soc Nephrol. 2018;13(1):182-192.
Thank you for explaining the mechanisms, but how does it differ in presentation compared to complement-fixing? Please see above
Ben Lomatayo
3 years ago
Alloantibodies to MHC molecules on the endothelial cells. This trigger strong responses which include cellular proliferation and activation of the intra-cellular signalling pathways that causes endothelial injury.
Increased expression of endothelial transcripts
Antibody mediated cellular cyto-toxicity ; FC receptor recruitment of the inflammatory cells such as neutrophils, macrophages, monocytes and NK cells
Complements independent pathways of endothelial activation
Sub-clinical, Chronic,Late presentation, less aggressive , C4d negative
Zahid Nabi
3 years ago
DSAs which do not bind complement can cause graft damage through antibody-dependent cellular cytotoxicity.
The innate immune cells, including neutrophils, macrophages, and natural killer cells, can bind to Fc fragments of DSAs, trigger degranulation, and release lytic enzymes, which cause tissue injury and cell death.
The other mechanism is graft injury by direct activation of endothelial proliferation through increasing vascular endothelial growth factor production, up regulating fibroblast growth factor receptor, and increasing its ligand binding as well as other signaling pathways for cellular recruitment .
Complement fixing DSA s usually are against Class 1 HLA antigens , are seen early and damages the graft in a more aggressive way as compared to non complement binding DSA s which usually cause a smoldering process leading to TG.
Excellent, yes, a less severe and late form of graft damage.
Batool Butt
3 years ago
ABMR (antibody-dependentacute or chronic) can occur due to complement-dependent and non-complement-dependent pathways upon binding of antibodies to mismatched donor antigens on the graft endothelium.
Non complement fixing DSAs can cause graft damage by 2 mechanisms either through antibody dependent cellular injury and/or direct endothelial damage
1-The innate immune cells, including neutrophils, macrophages, and natural killer cells, can bind to Fc fragments of DSAs, trigger degranulation, and release lytic enzymes, which cause tissue injury and cell death.
2-DSAs can cause graft injury by direct activation of endothelial proliferation through increasing vascular endothelial growth factor production, up regulating fibroblast growth factor receptor, and increasing its ligand binding as well as other signaling pathways for cellular recruitment. Differences between Complement fixing and non-complement fixing Antibodies.
a]complement fixing Antibodies cause acute or acute accelerated AMR with abrupt deterioration of allograft function. Usually occurring within 6 months, antibodies are usually anti HLA class I, either IgG 1 or IgG 3 preformed Antibodies, causes {acute glomerular capillaritis and PTC capillaritis} with polymorphonuclear cells infiltration, C4d staining will be positive.
b] Non-complement fixing Antibodies cause chronic AMR , presented with gradual , subtle deterioration of allograft function with proteinuria which is often in nephrotic range occurring mostly after 6 months, usually De novo DSAs against HLA class II, C4d staining will be negative.
REFERENCES:
1-Zhang R. Donor-Specific Antibodies in Kidney Transplant Recipients. Clin J Am Soc Nephrol. 2018;13(1):182-192.
2- Prof.ahmad Halawa lecture
AMR causes parenchymal renal damage either by complement dependent pathway or non complement dependent pathway ,determined by the nature of concerned DSAs[complement fixing vs non complement fixing}.
Non complement fixing .
several mechanisms have been proposed for complement independent tissue injury induced by DSAs:
1] Activated monocytes and macrophages infiltrate to graft tissues.
2] FC receptor protein is found on the surface of several cells as B lymphoctes,Natural killer cells and macrophages.
3] Endothelial activation via mTOR signaling pathway.
4] Endothelial damage related release of IL 6.IL11 and IL8 would attract CD4 T cell involvement.
5] Antibody -cell dependent cytotoxicity: this is mediated through innate immunity {Natural killer cells and macrophages},which get activated by binding to FC region of DSAs.
6] Antigen -Antibody interaction on endothelial cells is also known to increase Von Willibrand Factor [VWF] with resultant platelets activation producing TTP like picture.
7] Antigen -Antibody interaction on endothelial cells would result in externalization of P-selectin molecules resulting in increased leukocytes trafficking
references:
1]Prof.ahmad Halawa lecture.
2]Chethan Puttarajappa,Ron Shapiro, Henkie P. Tan.Antobody -mediated rejection in Kidney transplantation:A review.Journal of transplantation.2012
Presentation of non Complement fixing is usually Chronic AMR with TG as the underlying pathology with chronic slow deterioration of allograft function in contrast to complement fixing AMR which is presenting as acute severe deterioration of allograft function.
Ban Mezher
3 years ago
Presence of DSA ( preformed or de novo) associated with high risk of ABMR, graft dysfunction & poor graft outcome.
DSA can cause graft injury through 2 mechanism:
Complement dependent injury: this happened through binding of DSA & endothelial antigens leading to activation of classical complement pathway.
Non-complement dependent injury:
(a): Antibody-dependent cellular cytotoxicity: through binding of neutrophil, macrophages, & NK cells to Fc fragment of DSA leading to degranulation of these cells & release of lytic enzymes causing tissue injury.
(b) Direct activation of endothelial proliferation via increasing VEGF production, up regulation of FGF receptors & its ligand binding, in addition to involvement of other signaling pathway of cellular recruitment.
References:
Zhang R. Donor-Specific Antibodies in Kidney Transplant Recipients. Clin J Am Soc Nephrol, 2018;12: 182-192.
Abdulrahman Ishag
3 years ago
What is the mechanism of the damage induced by complement non-fixing DSA?
1-DSAs can cause graft damage through antibody-dependent cellular cytotoxicity.
The innate immune cells, including neutrophils, macrophages, and natural killer cells, can bind to Fc fragments of DSAs, trigger degranulation, and release lytic enzymes, which cause tissue injury and cell death.
This process can mediate smoldering damages to the endothelial cells and is proposed as an important pathogenesis in subclinical and chronic antibody-mediated rejection phenotypes .
2- DSAs can cause graft injury by direct activation of endothelial proliferation through increasing vascular endothelial growth factor production, up regulating fibroblast growth factor receptor, and increasing its ligand binding as well as other signaling pathways for cellular recruitment .
This pathogenesis may contribute to transplant glomerulopathy and vasculopathy that feature vascular intimal thickness with smooth muscle cell invasion.
Referance ;
1. Valenzuela NM, Reed EF: Antibodies in transplantation: The ef fects of HLA and non-HLA antibody binding and mechanisms of
injury. Methods Mol Biol 1034: 41–70, 2013
2. Hidalgo LG, Sis B, Sellares J, Campbell PM, Mengel M, Einecke G,Chang J, Halloran PF: NK cell transcripts and NK cells in kidney biopsies from patients with donor-specific antibodies: Evidence for NK cell involvement in antibody mediated rejection .
Thank you for explaining the mechanisms, but how does it differ in presentation compared to complement-fixing?
Mohamed Mohamed
3 years ago
1. What is the mechanism of the damage induced by complement non-fixing DSA? Introduction The diagnosis of AMR currently rests on circulating DSA, vascular injury, MVI & C4d. However, 50% of AMR episodes are missed due to the lack of sensitivity of C4d staining. Molecular endothelial-associated transcripts expressed in the grafts can also identify C4d negative AMR. Endothelial activation & innate immune infiltration play a central role in graft injury by DSAs. DSA is strongly associations with both AMR or graft loss. HLA class I DSA appear early, while HLA II DSA occur late post-transplant & associates with chronic graft dysfunction. Non-HLA antigens may also contribute to AMR. ================================================================= The mechanisms of antibody-mediated graft injury: Acute AMR is mainly driven by the effector functions of the Fc fragment of HLA antibodies. Fc-independent effects of antibodies cause chronic inflammation & proliferation. Complement fixation also depends on antibody titer & confounded by the presence of IgM. HLA DSAs trigger CDC of target lymphocytes, however endothelial cells (the primary target of antibody-mediated alloimmunity) are resistant to CDC in response to HLA antibodies. Endothelial cells may upregulate cytoprotective factors & survival signaling to prevent HLA antibody induced cytotoxicity. Complement fixing HLA I antibody augment basal P-selectin-mediated monocyte adhesion by binding to monocyte Fc gamma receptors (FcγRs). DSA subclasses that interact with FcγRs elicit recruitment of monocytes, induce late phase adhesion molecules & synthesis of chemo-attractants & inflammatory cytokines that promote inflammation. Complement fixing DSA carry a higher probability to develop AMR & progression to graft loss.
Cells recruited to the microvasculature in AMR are innate immune cells, NK cells & monocytes, which express FcγRs that allow for the recognition of DSA on the endothelial surface. NK cells almost exclusively express Fc gamma receptor IIIA (FcγRIIIA), commonly known as CD16. Patients expressing high-affinity variants of FcγRIIIA show more robust AMR responses in renal transplants. ===================================================== Complement-independent antibody-mediated endothelial & smooth muscle cell activation HLA DSA acts as agonists to induce intracellular signals in endothelial & smooth muscle cells. This is independent of the Fc fragment, & may be elicited by any IgG subclass.
Examples of such signals & their effects include:
– FAK (focal adhesion kinase): proliferation & migration of smooth muscle cells, & thus contributing to the neointimal changes seen in chronic rejection. —————————————————————————————————–
– MMP2 (matrix metalloproteinase-2) & nSMase2(neutral sphingomyelinase-2): HLA I antibody-induced smooth muscle cell proliferation —————————————————————————————————
– Type 1 endothelial cell activation induces rapid & transient induction of adhesion molecules & chemo-attractants
—————————————————————————————————-
— Type 2 activation requires protein synthesis resulting in chemokine & adhesion molecule expression over hours to days. —————————————————————————————————-
– HLA cross-linking trigger both type 1 & type 2 endothelial cell activation, causing macrophage recruitment to the allograft during HLA antibody- mediated injury. —————————————————————————————————– – Koenig et al. showed that when graft endothelial cells fail to provide an inhibitory signal through expression of HLA class 1 molecules used to educate recipient NK cells, NK cells are activated, leading to chronic vascular rejection. – This process of antibody-independent mechanism of NK cell activation is known as “missing self” (MS). – This focus on NK cells as primary architects of MVI, which may occur in the presence of DSA or MS—both of which are independently detrimental to allograft survival.
——————————————————————————————————- – Valenzuela et al. showed that the worse graft outcomes were observed in patients with complement-fixing DSA. – A novel finding in this study was the presence of non-complement-fixing DSA, the presence of MS shows a higher risk for graft loss in comparison with MS negative organs. This confirms that MS can synergize with weak DSA-mediated NK cell activation & translate into increased graft damage that accelerates the development of chronic lesions (IF/TA). – MS can more accurately predict the immunologic risk related to post- transplant DSAs,& pre-transplant. – Recipient killer cell Ig-like receptor typing might soon become the norm for the prediction of MS between recipient NK cells & donor endothelium. – DSA interpretation along with MS prediction does offer the potential to improve the identification of pathogenic DSAs. Conclusions Vasculitis & MVI are promising markers of endothelial injury in AMR. HLA antibody-induced endothelial cell inflammatory activation may promote the MVI & innate immune infiltration characteristic of AMR. Fc-mediated complement activation & engagement of Fc receptors act synergistically with endothelial activation to enhance inflammation & alloimmune damage. References 1. Valenzuela et al. Antibody-Mediated Graft Injury: Complement-Dependent and Complement-Independent Mechanisms Curr Opin Organ Transplant. 2014 February ; 19(1): 33–40. doi:10.1097/MOT.0000000000000040. 2. L. Hidalgo : Missing Self and DSA—Synergy of Two NK Cell Activation Pathways in Kidney Transplantation J Am Soc Nephrol. 2021 Feb; 32(2): 262–264. doi: 10.1681/ASN.2020121731: 10.1681/ASN.2020121731
Dear All
I’m not impressed. We have asked a simple question; we got a very complex answer.
Please go back to my lecture.
Damage induced by complement non fixing DSA.
Recruited inflammatory through Fc receptor and induced antibody mediated rejection.
Direct endothelial injury through VGEF activation.
The types of DSA either complement fixing or non fixing .
Non fixing one join with neutrophil through fc portion lead to apoptosis through inflammatory cells and cytokines
And activation of endothelium leads to VGEF proliferation and transplant glomerulopathy
Even in absence of complement activation, some DSAs can cause graft damage through antibody dependent cellular cytotoxicity. The innate immune cells, including neutrophils, macrophages, and natural killer cells, can bind to Fc fragments of DSAs, trigger degranulation, and release lytic enzymes, which cause tissue injury and cell death. This process can mediate smoldering damages to the endothelial cells and is proposed as an important pathogenesis in subclinical and chronic antibody-mediated rejection phenotypes .
Furthermore, DSAs can cause graft injury by direct activation of endothelial proliferation through increasing vascular endothelial growth factor production, upregulating fibroblast growth factor receptor, and increasing its ligand binding as well as other signaling pathways for cellular recruitment . This pathogenesis may contribute to transplant glomerulopathy and vasculopathy that feature vascular intima thickness with smooth muscle cell invasion.
the mechanism of the damage induced by complement non-fixing DSA
There are number of ways whereby antibodies interact with renal graft endothelium:
1. Complement activation by complement fixing DSA
2. ADCC : a non-fixing DSA binds to transplant endothelium with it’s FC portion, and interact with FC receptor of a leucocyte (NKC) with resultant apoptosis and release of cytokines that recruit further inflammatory cells and subsequent microvascular inflammation and tissue damage.
3. Endothelial Cell dysfunction: non-fixing DSA bind to graft endothelium and after signaling cascades promoting cellular proliferation and enhancement of monocyte’s binding to the endothelium with contribution to intimal proliferation and fibrosis.
4. Accommodation: DSA bind to the renal graft endothelium without evidence of injury. The phenomenon is not well understood.
What is the mechanism of the damage induced by complement non-fixing DSA?o DSAs can cause graft injury by fixing complement and activation of the complement cascade. However, non-complement fixing DSAs can also cause graft damage
o Non complement fixing DSAs are usually de novo directed against class 2 HLA antigens and cause chronic , slow, subclinical rejection and less severe form of graft damage with poor response of treatment.
A. Antibody dependent cell mediated cytotoxicity( ADCC):
It results from binding of Fc receptor of the DSAs with innate immune cells like NK cells, neutrophils, macrophage, causing degranulation, cellular injury and death.
B. Direct endothelial activation:
DSA directly binds to the endothelium leading to VEGF mediated proliferation and FGF receptor up regulation, both results in chronic vasculopathy and transplant glomerulopathy
References:
1. Rubin Zhang. Donor-Specific Antibodies in Kidney Transplant Recipients.
CJASN January, 2018
2. Handbook of kidney transplantation 6th edition
DSA can be complement fixing and complement non fixing…Complement fixing DSA cause antigen antibody interaction and cause graft injury…ABMR can be caused due to non complement fixing DSA also
The primary mechanism of action are
Non complement fixing DSA present in the late period after transplantation. They are usually due to de novo DSA against HLA class II namely IgG2 and IgG4. they cause C4d negative ABMR. They cause very slow graft dysfunction which are resistant to standard protocol of treatment. They are mainly responsible for cases of chronic transplant glomerulopathy..
Studies have proposed that complement-fixing IgG DSAs are associated with less rates of graft survival compared to non-complement-fixing DSAs, although the latter still portends a worse outcome when compared to recipients with negative DSA titre.
C1q positive and c1q negative types of DSA may suggest two different process causing CABMR.
C1q is the complement classic pathway’s component , the ability of DSA to bind C1q means its ability to activate the complement system which end to form membrane attack complex formation and subsequent lysis of renal endothelial cells, which lead relatively quickly to graft loss.
In non-complement state, C1q− dnDSAs could cause long-term graft loss independently of complement activation by inducing persistent microcirculation inflammation and antibody-dependent cell cytotoxicity or by direct activation of endothelial cell survival and proliferation.
Somes tudies report that the mechanism of injury in (CABMR), is that DSAs mediate injury by non–complement-mediated path ways or through direct interaction with endothelial cell targets with consequent activation of endothelial cell proliferation.
Cornell et al, in their study Showed that patient with positive DSA develop evidence of CABMR and transplant glomerulopathy (TG) even when complement pathway is inhibited by eculizumab .
Antibody binding to endothelium and will lead to cellular activation involving complement-dependent and –independent pathways leads to the recruitment of natural killer (NK) cells, polymorphonuclear neutrophils and macrophages, which participate in capillaritis and eventual tissue injury. The morphologic nature of endothelial cell injury in acute ABMR demonstrates platelet aggregation, thrombotic microangiopathy (TMA) and neutrophilic accumulation, resulting in an early pattern of cellular necrosis and a relatively rapid decline in allograft function. Chronic ABMR results from a repetitive pattern of chronic thrombotic events and inflammatory changes, which result in cellular injury and repair .
Sis et al report increased numbers of intraglomerular CD56+ natural killer (NK) cells in four of six cases of CAMR. This , other data point to a role for NK cells in CAMR, including increased levels of NK-cell-specific transcripts8 and experimental studies in mice which show that CAMR is dependent on NK cells and not complement fixation.
One report mention that there is evidence of at least three independent mechanisms of injury in CAMR:
1. classic complement fixation, as shown by the beneficial effects of anti-C5 therapy in antibody-mediated rejection in presensitized patients.
2. antibody-mediated rejection mediated by NK cells, independent of complement,
3. endothelial activation by antibody alone, best shown in endothelial cell cultures.
These mechanisms are each may has its own pathological signature in the biopsy, including C4d deposition, deposition of NK cells and markers of endothelial activation. Identification of specific mechanisms of injury in CAMR will help to determine the specific therapy. In addition to strategies to reduce circulating DSAs, complement-dependent CAMR could be addressed with complement inhibitor therapy, whereas Fc-receptor-dependent and NK-cell-dependent CAMR might require cell-directed or Fc inhibitor strategies.
Refrences :
1. Djamali A, Kaufman DB, Ellis TM, Zhong W, Matas A, Samaniego M: Diagnosis and management of antibody-mediated rejection: Current status and novel approaches. 14: 255–271, 2014 Am J Transplant.
2. Farkash EA, Colvin RB: Diagnostic challenges in chronic antibodymediated rejection. Nat Rev Nephrol 8: 255–257, 2012
3.Gwendaline Guidicelli et al , Non-Complement–Binding De Novo Donor-Specific Anti-HLA Antibodies and Kidney Allograft Survival, J Am Soc Nephrol. 2016 Feb; 27(2): 615–625,2015 Jun 5. doi: 10.1681/ASN.
as shown in the attached figure
antibodies cause destruction through 2 main mechanisms
noncomplement mediated is caused by 2 main pathways
Graft injury due to DSA occurs with or without complement fixation.
In case of absence of complement fixation, de novo type DSA against HLA class II lead to subclinical and chronic rejection. Cellular injury results from binding of Fc receptor of DSA with macrophages, neutrophils and ,NK cells leading to degranulation and cellular injury; AB dependent cell mediated cytotoxicity. Oher mechanism through binding of DSA to endothelial cells leading to activation with VEGF mediated proliferation in addition to upregulation of FGF receptor leading to transplant glomerulopathy
1) Antibody dependent cellular cytotoxicity:
Binding of innate immune cell such as neutrophil, macrophages and NK cells to FC fragment of donor specific antibodies, causes degranulation, release of lytic enzymes and cell death and sub-clinical decline of graft function not responding to treatment due to late chronic microvascular endothelial injuries lead to late AMR and chronic active AMR .Unlike complement fixing occur early and more sever .
2) Direct activation of endothelial proliferation by ↑ VEGF, increasing FGF receptors and its ligand binding resulting in TG and vascular intima thickness.This pathogenesis lead to chronic vasculopathy and transplant glomerulopathy .
complement independent antibodies induced cellular cytotoxicity and direct endothelial activation and proliferation through antibody-dependent cellular cytotoxicity. The innate immune cells recruitment including neutrophils, macrophages, and natural killer cells, and binding to Fc fragments of DSAs and trigger degranulation, release lytic enzymes, which cause tissue injury and cell death. usually due to denovo DSA class11 IgG subclass 4 activation which lead to subclinical progressive decline of graft function with poor response to treatment due to late chronic microvascular endothelial injuries and chronic vasculopathy the AMR phenotypes include late acute AMR, chronic active AMR, chronic transplant glomerulopathy.
Complement non-fixing DSA recruit NK cells, macrophages, and neutrophils through Fc receptors and lead to antibody dependent cellular toxicity that cause tissue injury, cellular recruitment and endothelial proliferation leading to acute ABMR with negative C4d deposit in PTC as well as chronic ABMR and eventual graft loss
Complement non-fixing DSA are usually of the IgG4 subclass or less commonly IgG2 ( which the latter might weakly bind complement ) , they are commonly targeting class 2 HLA on graft endothelium and can induce cell damage by the following mechanisms :
1- Ab dependant cellular cytotoxicity , by recuitinmg immune cells namely neutrophils , macrophages & NK cells that by degranulation and release of their lytic enzymes cause cell damage
2- direct endothelial cell activation and proliferation resulting in vasculopathy
in general it tends to occur later than the complement binding type , more associated with chronic changes and subclinical presentation and thereby slower graft loss
1- Non-complement fixing DSAs target the HLA class 2 on the endothelial cells. so recruiting innate immune cells that include NK cells, macrophages, and neutrophils by binding Fc receptors leads to antibody-dependent cellular toxicity.
2- Non-complement fixing DSAs have direct stimulation effects that cause tissue injury, cellular recruitment, and endothelial proliferation
– IgG has several subclasses (IgG1, -2, -3, and -4), and they have various abilities to activate complement and recruit effector cells through the Fc receptor. Although IgG2 can activate complement weakly, IgG4 does not activate complement at all, but both can recruit effector cells through the Fc receptor. IgG4 is also considered as a biomarker of matured alloresponse and associated with advanced stage of rejection. Lefaucheur et al. recently studied 125 patients with DSAs detected in the first year after kidney transplants: subclinical antibody-mediated rejection was driven by IgG4 iDSA. IgG4 iDSA was associated with later graft injury with increased transplant glomerulopathy and interstitial fibrosis/tubular atrophy. IgG4 iDSA–associated subacute and chronic phenotypes of antibody-mediated rejection
REF:
1. Donor-Specific Antibodies in Kidney Transplant RecipientsRubin Zhang
CJASN January 2018, 13 (1) 182-192; DOI: https://doi.org/10.2215/CJN.00700117
. Antibody-mediated rejection affects the renal allograft and leads to graft dysfunction & graft loss by 2 mechanisms, complement-dependent cytotoxicity ( c4d positive ) & non-complement-dependent cytotoxicity (c4d negative ), the latter has 2 pathways to affect the renal allograft involving antibody-mediated cellular cytotoxicity and direct endothelial activation with proliferation.
The mechanism of damage induced by complement non-fixing DSA includes:
1) Antibody dependent cellular cytotoxicity: In this, the Fc receptor of DSA is bound by the neutrophils, macrophages and (NK) cells leading to degranulation and lytic enzyme release causing tissue injury and cell death. (slow process, leading to subclinical & chronic AMR)
2) Direct stimulation of endothelial cell:
the endothelial cells are directly activated and proliferate due to increased (VEGF), upregulating (FGF) receptors, It leads to vasculopathy (increased vascular intime thickness with smooth muscle invasion) and transplant glomerulopathy.
Complement non binding DSA cause antibody mediated rejection activation of NK cells, macrophages and neutrophils through Fc fragment causing antibody dependent cellular toxicity.
The other mechanism through pleotropic effect and direct stimulation causing tissue damage, cellular recruitment and endothelial proliferation.
Complement non fixing DSA are usually class II and involve IgG2 and IgG4 subclasses.
leads to subclinical, chronic rejection with negative C4d deposition, transplant glomerulopathy and vasculopathy.
usually associated with slow graft dysfunction and tends to be persistent and less responsive to treatment with late graft loss.
Zhang R. Donor-specific antibodies in kidney transplant recipients. Clinical Journal of the American Society of Nephrology. 2018 Jan 6;13(1):182-92.
What is the mechanism of the damage induced by complement non fixing DSA
Complement fixing DSA
Complement non-fixing DSA
Reference
Rubin Zhang .Donor-Specific Antibodies in Kidney Transplant Recipients
CJASN January 2018, 13 (1) 182-192; DOI: https://doi.org/10.2215/CJN.00700117
Dear All,
Yes, lead to a subclinical progressive decline of graft function with poor response to treatment due to late chronic microvascular endothelial injuries and chronic vasculopathy the AMR phenotypes include late acute AMR, chronic active AMR, and chronic transplant glomerulopathy. You can tell clearly that non-complement fixing antibodies are also graft damaging, but the phenotypes of damage is different from complement-fixing antibodies, which are severe, and usually happens early.
the pathogeneses of antibody-mediated rejection include
1-Dirct complement-dependent cytotoxicity, C1q binding with C4D positive characterized by aggressive type of accelerated acute or hyper-acute AMR with early graft loss usually due to performed DSA with subclass IgG3 and its direct complement dependent effectors cells activations through the FC receptors binding activity in previously sensitized recipient with high PRA% of preformed DSAs which could include both class1 ,class2 DSAs.
2-complement independent antibodies induced cellular cytotoxicity and direct endothelial activation and proliferation through antibody-dependent cellular cytotoxicity. The innate immune cells recruitment including neutrophils, macrophages, and natural killer cells, and binding to Fc fragments of DSAs and trigger degranulation, release lytic enzymes, which cause tissue injury and cell death. usually due to denovo DSA class11 IgG subclass 4 activation which lead to subclinical progressive decline of graft function with poor response to treatment due to late chronic microvascular endothelial injuries and chronic vasculopathy the AMR phenotypes include late acute AMR, chronic active AMR, chronic transplant glomerulopathy.
Risk factors for deno DSA
1-Higher HLA mismatch especially calss11 DQ mismatch.
2- nonadherences to immunosuppression
3-graft inflammation, due to viral infection, previous TCMR, ischemic injuries
Which increased the graft immunogenicity.
References
1-Lefaucheur C, Viglietti D, Bentlejewski C, et al. IgG Donor-Specific Anti-Human HLA Antibody Subclasses and Kidney Allograft Antibody-Mediated Injury. J Am Soc Nephrol. 2016;27(1):293-304.
2-Zhang, Rubin. “Donor-Specific Antibodies in Kidney Transplant Recipients.” Clinical journal of the American Society of Nephrology: CJASN vol. 13,1 (2018): 182-192
Thanks, Saja
Yes, lead to a subclinical progressive decline of graft function with poor response to treatment due to late chronic microvascular endothelial injuries and chronic vasculopathy the AMR phenotypes include late acute AMR, chronic active AMR, and chronic transplant glomerulopathy.
The pathogeneses of antibody-mediated rejection include not only complement-dependent cytotoxicity, but also complement independent pathways of antibody-mediated cellular cytotoxicity and direct endothelial activation and proliferation.
C1q nonbinding donor-specific antibodies correlate with subclinical or chronic antibody-mediated rejection and late graft loss, and non -complement binding IgG4 and igG2 donor-specific antibodies are more correlated with subclinical or chronic antibody mediated rejection and transplant glomerulopathy as well.
Although activation of the complement pathway by binding of DSA to endothelial cell antigens is the main mechanism of graft injury in AMR, even in the absence of complement activation, some DSAs can lead to graft damage through antibody dependent cellular cytotoxicity. Binding of the innate immune cells, consists of neutrophils, macrophages, and natural killer cells, to Fc fragments of DSAs, triggers degranulation, and releases lytic enzymes, which lead to tissue injury and cell death. This silent and gradual process can result in endothelial cell damage and is proposed as an important pathogenesis in subclinical and chronic AMR phenotypes. Another complement independent mechanism is direct stimulation and activation of endothelial proliferation by DSAs with pleotrophic effects through increasing vascular endothelial growth factor production, upregulating fibroblast growth factor receptor, and increasing its ligand binding as well as other signaling pathways for cellular recruitment that ultimately lead to graft injury, and it may contribute to transplant glomerulopathy and vasculopathy, and present as peritubular arteries C4d negative AMR.
Binding of donor-specific antibodies (DSAs) to kidney allograft endothelial cells that does not activate the classic complement Cascade can trigger the recruitment of innate immune effectors, including NK cells. Activated NK cells contribute to microvascular inflammation leading to chronic AMR. Recipient NK cells can also trigger antibody-independent microvascular inflammation by sensing the absence of self HLA class I molecules (“missing self”) on allograft endothelial cells. As a result, the assessment of missing self at the time of diagnosis of chronic AMR identifies patients at higher risk for kidney transplant failure.
However, compared with C1q nonbinding DSAs, C1q binding DSAs are associated with significantly higher risk of antibody-mediated rejection, severe tissue injury, and graft loss.
I can summarise your reply.
It gives a less severe and more chronic form of graft damage.
Well done
first mechanism :
as C1q is the complement classic pathway’s first protagonist, the ability of DSA to bind C1q in vitro should determine its ability to activate the complement cascade in vivo, before membrane attack complex formation and subsequent lysis of renal endothelial cells, which lead relatively quickly to graft loss.
second mechanism:
C1q− dnDSAs could cause long-term graft loss independently of complement activation by inducing persistent microcirculation inflammation and antibody-dependent cell cytotoxicity, or by direct activation of endothelial cell survival and proliferation.
Thank you for explaining the mechanisms, but how does it differ in presentation compared to complement-fixing?
acute antibody-mediated rejection was mainly driven by IgG3 , whereas subclinical antibody mediated rejection was driven by IgG4 .
IgG3 was associated with a shorter time to rejection, increased microcirculation injury, and positive C4d deposits, which indicate the complement-dependent cytotoxicity.
IgG4 was associated with later graft injury with increased transplant glomerulopathy and interstitial fibrosis/tubular atrophy.
There are two mechanisms for injury and damage induced by complement
non-fixing DSA:
1) Antibody dependent cellular cytotoxicity:
Binding of innate immune cell such as neutrophil, macrophages and NK cells to FC fragment of donor specific antibodies, causes degranulation, release of lytic enzymes and cell death and sub clinical and CAMR.
2) Direct activation of endothelial proliferation by ↑ VEGF, increasing FGF receptors and its ligand binding resulting in TG and vascular intima thickness.
Thank you for explaining the mechanisms, but how does it differ in presentation compared to complement-fixing?
Ab mediated rejection by anti HLA which could be FC portion (complement fixing) or non complement (other mechanism ) depend on subclass of anit HLA , titre and affinity of Ab to react with endothelial cell of allograft .
complement independent :
1- HLA promote smooth muscle cell proliferation through focal adhesion kinase which lead to neointimal change especially in chronic Ab mediated rejection and recent evidence implicate role of mellatoproteinase and neutral sphingomyelinase in smooth cell proliferation .
2- HLA crosslinking activated Rho kinase ,myocin light chin kinase in calcium independent manner which stimulate stress fiber formation .
3-HLA cross linking lead to macrophage recruitment to allograft and trigger two type of activation type one (rapid and transient induction of adhesion molecules and type 2 (lead to chemokine and adhesion molecule).
Dear All
Most of you gave detailed information about the mechanism of non complement fixing antibodies on the endothelial graft cells few gave a simple comprehensive answer which will be useful if you add the following scheme which helps you as practicing nephrologists:
1. Possible eitiology
2HLA class
3. MFI ,cross match
4.Time of appearance
5.which Effector cells ( Innate immunity)
6.Time of start of graft dysfunction ,pathology
7.course and response to treatment
By addressing these point a diagnosis and management will be amenable.
Thank you for explaining the mechanisms, but how does it differ in presentation compared to complement-fixing?
–In absence of complement activation, some DSAs can cause graft damage through antibody-dependent cellular cytotoxicity. The innate immune cells, including neutrophils, macrophages, and natural killer cells, can bind to Fc fragments of DSAs, trigger degranulation, and release lytic enzymes, which cause tissue injury and cell death. This process can mediate smoldering damages to the endothelial cells and is proposed as an important pathogenesis in subclinical and chronic antibody-mediated rejection phenotypes .
-Furthermore, DSAs can cause graft injury by direct activation of endothelial proliferation through increasing vascular endothelial growth factor production, upregulating fibroblast growth factor receptor, and increasing its ligand binding as well as other signaling pathways for cellular recruitment . This pathogenesis may contribute to transplant glomerulopathy and vasculopathy that feature vascular intima thickness with smooth muscle cell invasion. The latter two complement-independent mechanisms can explain the clinical phenotypes of antibody-mediated rejection with negative C4d staining in peritubular capillaries.
Reference:
-Rubin Zhang .Donor-Specific Antibodies in Kidney Transplant Recipients
CJASN January 2018, 13 (1) 182-192; DOI: https://doi.org/10.2215/CJN.00700117
Very good
What is the mechanism of the damage induced by complement non-fixing DSA?Non- HLA antibodies against surface may fixing complement or mediated ADCC depend on signaling capacity and biological function of the ligand as with HLA1 molecules. For example angiotensin 11 recptor AT1 antibodies are well established against which promote HTN and contribute to renal allograft injury.
antibodies upregulates adhesion molcules and cytokines on endothelial cells but when the target is unkonown the precise mechanism remain elusive to date ,little has been studied on the action of non HLA antibodies during humoral alloimmune response.
example of non-HLA antibodies MICA and MICB that function as ligands for the NK cells receptors, these antibodies associated with chronic rejection .
non HLA antibodies in transplantion can be directed against either polymorphism or non allelic proteins . The development of antibodies against non polymorhoric target may be due to upregularation during inflammation , in response to transplantaion or when protiens are exposed to the immune system during injury , it is thought that intergraft microenviroment or rejection may break humoral tolerance to autoantigens,
non HLA antiendotheialial cell antibodies has increase incidence of failed graft.
References1. Zhang Q, Cecka JM, Gjertson DW, Ge P, Rose ML, Patel JK, et al. HLA and MICA: targets of antibody-mediated rejection in heart transplantation. Transplantation. 2011;91:1153–1158. [PMC free article] [PubMed] [Google Scholar]
2. Cardarelli F, Pascual M, Tolkoff-Rubin N, Delmonico FL, Wong W, Schoenfeld DA, et al. Prevalence and significance of anti-HLA and donor-specific antibodies long-term after renal transplantation. Transpl Int. 2005;18:532–540. [PubMed] [Google Scholar]
3. Everly MJ, Everly JJ, Arend LJ, Brailey P, Susskind B, Govil A, et al. Reducing de novo donor-specific antibody levels during acute rejection diminishes renal allograft loss. Am J Transplant. 2009;9:1063–1071. [PubMed] [Google Scholar.
Thank you for explaining the mechanisms, but how does it differ in presentation compared to complement-fixing?
*The pathogeneses of antibody-mediated rejection includes not only complement-dependent cytotoxicity, but also complement-independent pathways of antibody-mediated cellular cytotoxicity and direct endothelial activation and proliferation.
*C1q nonbinding donor-specific antibodies correlate with subclinical or chronic antibody-mediated rejection and late graft loss.
*in absence of complement activation, some DSAs can cause graft damage through antibody-dependent cellular cytotoxicity.
* innate immune cells, including neutrophils, macrophages, and natural killer cells, can bind to Fc fragments of DSAs, trigger degranulation, and release lytic enzymes, which cause tissue injury and cell death.
*This can mediate damages to the endothelial cells causing subclinical and chronic antibody-mediated rejection.
*DSAs can also cause graft injury by direct activation of endothelial proliferation through increasing vascular endothelial growth factor production, upregulating fibroblast growth factor receptor, and increasing its ligand binding as well as other signaling pathways for cellular recruitment .
* complement-independent mechanisms can explain the clinical phenotypes of antibody-mediated rejection with negative C4d staining in peritubular capillaries.
*HLA antibodies act as agonists to induce intracellular signaling in endothelial and smooth muscle cells.
these effects are independent of the Fc fragment, and may therefore be elicited by any IgG subclass.
*HLA I antibodies promote focal adhesion kinase (FAK)-dependent proliferation and migration of smooth muscle cells, which may contribute to the neointimal changes seen in chronic rejection.
*Recent evidence has also implicated matrix metalloproteinase-2 (MMP2) and neutral sphingomyelinase-2 (nSMase2) in HLA I antibody-induced smooth muscle cell proliferation in vitro and in vivo , which is interesting in clinical observations of increased intragraft expression of MMP2 during AMR .
*addition to early endothelial activation, HLA I antibodies induce late phase adhesion molecules and synthesis of chemoattractants and inflammatory cytokines that promote inflammation.
*HLA I crosslinking activated the transcription factor cAMP response element binding protein (CREB), which lead to increased adhesion molecule and chemokine expression by microvascular endothelium, and monocyte adhesion
*studies found increased synthesis of cytokines and chemokines by endothelial cells from other vascular beds upon exposure to HLA antibodies
with Production of inflammatory mediators by endothelial cell antibodies stimulated with HLA antibodies.
Reference
Rubin Zhang.Donor-Specific Antibodies in Kidney Transplant Recipients. CJASN January 2018, 13 (1) 182-192.
Nicole M Valenzuela, Jeffrey T McNamara, and Elaine F Reed.Antibody-Mediated Graft Injury: Complement-Dependent and Complement-Independent Mechanisms.Curr Opin Organ Transplant. 2014 Feb; 19(1): 33–40.
Well done
1-HLA antibodies act as agonists to induce intracellular signaling in endothelial and smooth muscle cells. these effects are independent of the Fc fragment, and may therefore be elicited by any IgG subclass.
2-HLA I antibodies promote focal adhesion kinase (FAK)-dependent proliferation and migration of smooth muscle cells ,which may contribute to the neointimal changes seen in chronic rejection.
3-Recent evidence has also implicated matrix metalloproteinase-2 (MMP2) and neutral sphingomyelinase-2 (nSMase2) in HLA I antibody-induced smooth muscle cell proliferation in vitro and in vivo ,which is interesting in light of clinical observations of increased intragraft expression of MMP2 during AMR .
4-Cell proliferation and migration are dependent upon reorganization of the cytoskeleton with the suggestion that ERK1/2 is a critical regulator of endothelial cytoskeletal changes, migration and motility .
5-macrophages are key immune mediators of graft injury. Endothelial cells actively regulate infiltration of leukocytes from the bloodstream into the tissue.
6-Type 1 endothelial cell activation involves rapid and transient induction of adhesion molecules and chemoattractants, while type 2 activation requires protein synthesis resulting in chemokine and adhesion molecule expression over the course of hours or days.
7-Emerging evidence indicates that HLA crosslinking can trigger both type 1 and type 2 endothelial cell activation, providing some insight into the mechanisms of macrophage recruitment to the allograft during HLA antibody-mediated injury.
8-HLA I crosslinking by antibodies triggers rapid endothelial exocytosis (<30min, type 1 activation) leading to cell surface presentation of the adhesion molecule P-selectin and release of vWF from aortic, venous and microvascular endothelial cells .This induction did not require the Fc portion of the antibody, suggesting that all IgG subclasses can elicit pathogenic effects by direct endothelial cell activation.
9-HLA I antibodies induce late phase adhesion molecules and synthesis of chemoattractants and inflammatory cytokines that promote inflammation.
10- also found increased synthesis of cytokines and chemokines by endothelial cells from other vascular beds upon exposure to HLA antibodies .
Reference:
Antibody-Mediated Graft Injury: Complement-Dependent and Complement-Independent Mechanisms
Nicole M Valenzuela, Jeffrey T McNamara, and Elaine F Reed.
You described the direct effect of the non complement fixing antibodies IGg 2,4 on the endothelial cells
What about the innate immunity cells , is the mechanism different?
Can you correlate the mechanism with the clinical setup
Are there predisposing factors.
innate immune cells, including neutrophils, macrophages, and natural killer cells, can bind to Fc fragments of DSAs, trigger degranulation, and release lytic enzymes, which cause tissue injury and cell death. *This can mediate damages to the endothelial cells causing subclinical and chronic antibody-mediated rejection.
The etiology due to ischemia-reperfusion injury, non-adherence to IS or viral infection
The rejection is chronic late in presentation lead to late AMR or chronic active AMR.
It slowly progressed but eventually lead to graft loss
The mechanism of injury by antibody-mediated cellular toxicity or direct endothelial damage and swelling.
HLA antibodies act as agonists to induce intracellular signalling in endothelial and smooth muscle cells. This is independent of the Fc fragment. Any IgG class may elicit this. FAK (focal adhesion kinase) and MMP-2 (matrix metalloproteinase-2) and nSMase2 (neutral sphingomyelinase) may play role. active MMP2 acts on nSMase to stimulate ceramide, which is itself pro-inflammatory. Class I HLA antibodies promote FKA dependent proliferation and migration of smooth muscles.
In heart transplantation, intracapillary macrophages are an important hallmark of AMR in cardiac allografts.
Valenzuela NM, McNamara JT, Reed EF. Antibody-mediated graft injury: complement-dependent and complement-independent mechanisms. Curr Opin Organ Transplant. 2014 Feb;19(1):33-40. doi: 10.1097/MOT.0000000000000040. PMID: 24316758; PMCID: PMC4080796.
but how does it differ in presentation compared to complement-fixing?
Even in absence of complement activation, some DSAs can cause graft damage through antibody-dependent cellular cytotoxicity. The innate immune cells, including neutrophils, macrophages, and natural killer cells, can bind to Fc fragments of DSAs, trigger degranulation, and release lytic enzymes, which cause tissue injury and cell death. This process can mediate damages to the endothelial cells and have an important role in pathogenesis of subclinical and chronic antibody-mediated rejection phenotypes
Furthermore, DSAs can cause graft injury by direct activation of endothelial proliferation through increasing vascular endothelial growth factor production, upregulating fibroblast growth factor receptor, and increasing its ligand binding as well as other signaling pathways for cellular recruitment
This pathogenesis may contribute to transplant glomerulopathy and vasculopathy that feature vascular intima thickness with smooth muscle cell invasion. The latter two complement-independent mechanisms can explain the clinical phenotypes of antibody-mediated rejection with negative C4d staining in peritubular capillaries.
Reference
Rubin Zhang. Donor-Specific Antibodies in Kidney Transplant Recipients. Clin J Am Soc Nephrol 13: 182–192, 2018. doi: https://doi.org/10.2215/CJN.00700117
Very good concise and clear
Can you relate the mechanism explained to the clinical scenario of the patient along with the work up plan ie possible eitiology
Type of HLA class
Time of formation
Effector cells
Cross match
Time of rejection
Type of rejection
Graft outcome
Response to treatment
Complement fixing
HLA A,B ,C
All nucleated cells
early presentation of acute AMR
rapid graft dysfunction.
More responsive to the treatment of rejection
Possitive T-cell Crossmatch.
IgG 1 ,IgG 3subclasses
Early graft loss
Complement non fixing
HLA DR, DQ, DP
Antigen presenting cells
late presentation AMR
Chronic AMR
slowly graft dysfunction
less responsive to the treatment of rejection
Positive B-cell Crossmatch
IgG 2 , IgG 3
Late graft loss
Sorry complement non fixing IgG subclasses IgG 2,IgG 4
DSA can cause graft injury by both complement fixation and without complement fixation.
DSA can cause graft injury without complement fixation, which are generally denovo variety with dsa against HLA class 2 and cause subclinical and chronic rejection.
A.ADCC-antibody dependant cell mediated cytotoxicity, which is due to binding of Fc receptor of dsa with neutrophils,macrophage, NK cell with degranulation and cellular injury.
B.DIRECT ENDOTHELIAL ACTIVATION-DSA bound to endothelium and directly activates endothelium leading to VEGF mediated proliferation and FGF receptor upregulation, both leading to transplant glomerulopathy.
Excellent
Short and sweet
1. What is the mechanism of the damage induced by complement non-fixing DSA?
Antibody mediated rejection, leading cause of graft dysfunction and graft loss post-trasnplant, can be either due to complement dependent cytotoxicity, or due to non-complement dependent pathways involving antibody-mediated cellular cytotoxicity and direct endothelial activation with proliferation.
The mechanism of damage induced by complement non-fixing DSA includes:
1) Antibody dependent cellular cytotoxicity: In this, the Fc receptor of DSAs (against class II HLA) gets bound by the neutrophils, macrophages and CD3-CD16+ natural killer (NK) cells leading to degranulation and lytic enzyme release causing tissue injury and cell death. It is usually a slow process, leading to subclinical and chronic AMR phenotypes.
2) Direct stimulation of endothelial cell: In this, the endothelial cells are directly activated and proliferate due to increased vascular endothelial growth factor (VEGF), upregulating fibroblast growth factor (FGF) receptor, increasing ligand binding and other pathways for leukocyte recruitment further causing tissue injury and endothelial proliferation. It leads to vasculopathy (increased vascular intime thickness with smooth muscle invasion) and transplant glomerulopathy.
Complement non-fixing DSA present with C4d negative staining in peritubular capillaries, hence designated C4d negative AMR. These are usually due to class II DSAs, appearing later in post-transplant period, involving IgG subclasses IgG2 and IgG4, present with chronic and subclinical phenotypes having slowly progressing graft dysfunction and late graft loss with poor response to treatment.
References:
1) Zhang R. Donor-Specific Antibodies in Kidney Transplant Recipients. Clin J Am Soc Nephrol. 2018 Jan 6;13(1):182-192. doi: 10.2215/CJN.00700117. Epub 2017 Apr 26. PMID: 28446536; PMCID: PMC5753302.
2) Valenzuela NM, Reed EF. Antibodies in transplantation: the effects of HLA and non-HLA antibody binding and mechanisms of injury. Methods Mol Biol. 2013;1034:41-70. doi: 10.1007/978-1-62703-493-7_2. PMID: 23775730; PMCID: PMC3879955.
3) Valenzuela NM, McNamara JT, Reed EF. Antibody-mediated graft injury: complement-dependent and complement-independent mechanisms. Curr Opin Organ Transplant. 2014 Feb;19(1):33-40. doi: 10.1097/MOT.0000000000000040. PMID: 24316758; PMCID: PMC4080796.
Very good
You are excellent Amit
v Mechanism of graft injury in non -complement fixing antibodies:
1. Recruitment of inflammatory cells as neutrophils, macrophages and NK cells that bind to Fc portion of DSA that lead to their degranulation and release of proteolytic enzymes that induce graft damage.
2. Endothelial cell activation and swelling by alloantibodies which leads to microvascular inflammation and stimulation of inflammatory cascade with further recruitment of inflammatory cells.
3. T cell activation (antibody dependent cellular toxicity).
4. Endothelial cell associated transcripts.
v Difference between complement fixing and non fixing antibodies mediated rejection:
I can not copy the table, so i attached a screen shot of it.
This is excellent, Mai
Short, sweet and without jargon.
Thanks dear professor
ABMR can be considered as the main cause of graft loss ,there are different forms of ABMR that occurs post kidney transplant depending on the time of the rejection,IgG classes and the strength of the antibodies detected all these factors can cause hyperacute,accelerated early acute,and late acute rejection.
Late acute rejection mainly caused by de novo DSA which is also responsible for chronic ABMR and glomerulopathy.
Complement fixing activation is the triggering factor for ABMR it has C4d deposition while non complement fixing activation also responsible for ABMR by subsequent endothelial activation and proliferation leading to inflammation in micro circulation.
Refrence
_Zhang R. at al , Donor Specific Antibodies in Kidney Transplant Recipients. Clin J Am Soc Nephrol. 2018;13(1):182_192.
Well done Tahani
complement-independent cytotoxicity is through 2 mechanisms:
1. through innate immune cells, including neutrophils, macrophages, and natural killer cells, which bind to Fc fragments of DSAs, triggering degranulation, and release of lytic enzymes, which cause tissue injury and cell death. This results in subclinical and chronic antibody-mediated rejection phenotypes
2. through direct activation of endothelial proliferation through increasing vascular endothelial growth factor production, upregulating fibroblast growth factor receptor, and increasing its ligand binding as well as other signaling pathways for cellular recruitment. This can result in transplant glomerulopathy and vasculopathy that feature vascular intima thickness with smooth muscle cell invasion .
How the rejection caused by complement-fixing antibodies differs from complement non-fixing?
C1q binding DSA and Complement binding IgG3 are closely associated with acute AMR, more severe graft injuries, and early graft failure.
C1q nonbinding and non-complement binding IgG4 DSA correlate with subclinical or chronic AMR and late graft loss. The non-complement binding IgG4 DSA are more correlated transplant glomerulopathy.
Zhang R. Donor-Specific Antibodies in Kidney Transplant Recipients. Clin J Am Soc Nephrol. 2018;13(1):182-192. doi:10.2215/CJN.00700117
Yes, gives less severe and looks like a chronic form of graft damage
C1q binding indicates the clinical relevance of de novo DSA. Complement non fixing DSA can cause long term graft loss independent of complement activation by inducing persistent microvascular inflammation and antibody dependent cell cytotoxicity, or by direct activation of endothelial cell survival and proliferation.
This is in contrast to complement fixing DSA which cause graft loss by activating the complement cascade in Vito , before membrane attack complex formation and leading to subsequent lysis of renal endothelial cells, resulting in graft loss.
Complement non-fixing DSA target HLA II on endothelial cells. Natural killer cells, macrophages and neutrophils are recruited by these DSA through Fc receptors, resulting in antibody dependent cell toxicity. Complement non-fixing DSA also directly stimulate tissue injury, cell recruitment and endothelial proliferation. These 2 mechanisms play a role in
Reference :
This is excellent, Nandita
Short, sweet and without jargon.
What is the mechanism of the damage induced by complement non-fixing DSA?Complement nonbinding DSAs target the class 2 HLA on endothelial cells and recruit innate immune cells (NK cells, macrophages, and neutrophils) through Fc receptors and lead to antibody-dependent cellular toxicity.
• In addition, complement nonbinding DSAs have direct stimulation effects that cause tissue injury, cellular recruitment, and endothelial proliferation.
• The latter two mechanisms play an important role in acute AMR with negative C4d deposit in peritubular capillaries as well as cAMR, transplant glomerulopathy, vasculopathy and possible immunological damage caused by APC, antigen-presenting cells; NK, natural killer cells.
References:
1-Applied Transplant Immunology; Case-based Discussion (Part 2) By professor : Ahmed Halawa.
Yes, less severe and late form of graft damage
What is the mechanism of the damage induced by complement non-fixing DSA?
# The presence of DSA, either preformed or de novo is biomarker for predicting poor transplant outcomes, including high incidence of ABMR.
*The risk factors for de novo DSA include the following:
(1) high HLA mismatches (especially DQmismatches) (2) inadequate immunosuppression and nonadherence
(3) graft inflammation, such as viral infection, cellular rejection, or ischemia injury, which can increase graft immunogenicity
* De novo DSAs are predominantly directed to donor HLA class 2 mismatches and usually occur during the first year of kidney transplant, but they can appear anytime
** DSA can cause graft injury through 2mechanism:
# Complement fixing antibody cause graft damage through:
binding of DSA to antigen expressed on allograft endothelial cells can activate classic complement pathway, a key pathologic process of acute antibody mediated rejection phenotypes
# Non complement fixing antibody can cause graft damage through:
* Antibody dependent cellular cytotoxicity, in which innate immune cells including neutrophils, macrophages, and natural killer cells, bind to Fc fragments of DSAs, trigger degranulation and release lytic enzymes, which cause tissue injury and cell death. This process can mediate damages to the endothelial cells and is proposed as an important pathogenesis in subclinical and chronic antibody mediated rejection phenotypes
* DSAs can cause graft injury by direct activation of endothelial proliferation through increasing vascular endothelial growth factor production, upregulating fibroblast growth factor receptor, and increasing its ligand binding as well as other signaling pathways for cellular recruitment
This pathogenesis may contribute to transplant glomerulopathy and vasculopathy that feature vascular intima thickness with smooth muscle cell invasion.
The latter two complement independent mechanisms can explain the clinical phenotypes of antibody mediated rejection with negative C4d staining in peritubular capillaries.
Dr. Rubin Zhang, Section of Nephrology, Department of Medicine, Tulane Transplant Institute, Tulane University School of Medicine, 1430 Tulane Avenue, SL-45, New Orleans, LA 70112. Email: ude.enalut@gnahzr
Copyright © 2018 by the American Society of Nephrology
Yes, less severe and late form of graft damage
DSAs are well-known biomarkers of antibody-mediated rejection, and they have been linked to lower graft survival and loss rates in studies.
In addition to complement-dependent cytotoxicity, antibody-mediated rejection can result in direct endothelial activation and proliferation, as well as tissue and cell injuries. Neutrophils, macrophages, and natural killer cells can bind to DSA Fc fragments and trigger degranulation and the release of a lytic enzyme (innate immune response), which can result in tissue and cell injuries as well as direct stimulation of endothelial growth factor secretion and proliferation.
Some DSAs have the potential to produce graft destruction even in the absence of complement activation.
The cytotoxicity of cells that is mediated by antibodies:
The innate immune cells, which include neutrophils, macrophages, and natural killer cells, are responsible for protecting the body from infection.
may attach to Fc segments of DSAs, causing degranulation and the release of lytic enzymes, among other things can induce tissue harm and cell death in a variety of ways
DSAs have the potential to induce graft damage via the stimulation of endothelial proliferation.
boosting the synthesis of vascular endothelial growth factors and upregulating the development of fibroblasts
enhancing the ligand-binding affinity of the factor receptor, as well as additional signalling pathways for the factor.
References:
Zhang R. Donor-Specific Antibodies in Kidney Transplant Recipients. Clin J Am Soc Nephrol.
Thank you for explaining the mechanisms, but how does it differ in presentation compared to complement-fixing?
▪︎Antibodies to HLA are IgG class
▪︎ IgG occurs as a monomer and can be devided into four subclasses
▪︎ IgG1 and IgG3 are the main activator of the classical Complement PW [1].
▪︎IgG2 and IgG4 antibodies do not fix complement and bind very poorly to activating FcγR.
▪︎ HLA antibodies also act as agonists to induce intracellular signaling in endothelial and smooth muscle cells. Notably, these effects are independent of the Fc fragment, and may therefore be elicited by any IgG subclass.
▪︎Complement non fixing Donor specific HLA antibodies stimulate endothelial cell signaling, including rapid exocytosis of P-selectin and production of chemokines, leading to inflammatory activation and leukocyte recruitment [2].
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Ref:
[1]Mark Pearland. ” Basic and Clinical Immunology “.2nd edition
[2] Nicole M Valenzuela, Jeffrey T McNamara, and Elaine F Reed “Antibody-Mediated Graft Injury: Complement-Dependent and Complement-In dependent Mechanisms”.
Thank you for explaining the mechanisms, but how does it differ in presentation compared to complement-fixing?
· Mechanism: identification of Fc portion of the AB by the innate immune cells – tissue injury and cell death.
· This mechanism is implicated in subclinical and chronic antibody-mediated rejection phenotypes and c4d negative ABMR
2. . Direct activation of endothelial proliferation
· Increases the production of vascular endothelial growth factor, fibroblast growth factor receptor upregulation, and increases its ligand binding as well as other signaling pathways for cellular recruitment
· This may cause transplant glomerulopathy, vasculopathy, and C4d negative ABMR
Humoral immunity may find different pathways for antibody production, either primarily (autoantibodies) or by exposing donor antigens outside the HLA complex (alloantibodies), inducing antibody-mediated rejection. This response is quite heterogeneous and multifactorial, involving increased or decreased expressions, ischemic injury, and inflammatory state of the allograft.
Angiotensin type 1 receptor (AT1R)
– Triggers apparently vascular lesion refractory to the use of corticosteroids
– Malignant hypertension
– Major vascular rejection
– Usually does not use complement to trigger the lesion
– May trigger acute rejection in the first 4 months or late after 3 years of transplantation
– Appears to be related to recurrent focal and segmental glomerulosclerosis
– When associated with DSA/HLA, the prognosis worsens
– Treatment is based on a combination of plasmapheresis, intravenous immunoglobulin, and losartan
Perlecan
– Important component of vascular endothelium
– Predominant activity in the LG3 subdomain
– LG3 suggests being a regulator of vascular remodeling
– May lead to vascular lesions and synergize with HLA-DSA, similar to what occurs with AT1R antibodies
Collagen
– Expresses metalloproteases that modify collagen and lead to the production of autoantibodies
– In lung transplantation, it is common to trigger bronchiolitis obliterans syndrome
– In kidney transplantation, it is common to cause transplantation glomerulopathy
– Uses the Th17 axis and interleukins can lead to direct graft injury (IL17) or autoantibody production (IL23)
Autoantibody production in transplantation
– Ischaemia reperfusion injury
– Alloimmunity x Autoimmunity
– Extracellular vesicles
– Th17 cells and tertiary lymphoid tissues
All of these paths can occur autoantibody production might occur via several mechanisms, including extracellular vesicles, apoptotic bodies, cross-reactivity between self and foreign antigens, and the interplay between innate and adaptive immunity induced by the Th17 IL 12-17-23 path.
Thank you for explaining the mechanisms, but how does it differ in presentation compared to complement-fixing?
Please see above
HLA antibodies and non-HLA Abs-binding endothelial cells are associated with the activation of complement and non complement system and lead to early AMR.
Complement non fixing DSA igG4 are associated with late graft loss and chronic AMR.
it’s also assessed with transplant glomerulopathy.
Pathogenesis of antibody-mediated rejection include complement-dependent cytotoxicity and complement-independent pathways of antibody-mediated cellular cytotoxicity and direct endothelial activation and proliferation.
Donor-specific anti-endothelial cell Abs detected in the pre-transplant evaluation.
Complements factor C3c, C3d and immunoglobulin G (IgG) deposit on T and B cells are detected on EPCs; it’s can detected by complement-dependent cytotoxicity assay.
References
Zhang R. et al,Donor-Specific Antibodies in Kidney Transplant Recipients. Clin J Am Soc Nephrol. 2018;13(1):182-192.
Thank you for explaining the mechanisms, but how does it differ in presentation compared to complement-fixing?
Please see above
Thank you for explaining the mechanisms, but how does it differ in presentation compared to complement-fixing?
Please see above
Sub-clinical, Chronic,Late presentation, less aggressive , C4d negative
DSAs which do not bind complement can cause graft damage through antibody-dependent cellular cytotoxicity.
The innate immune cells, including neutrophils, macrophages, and natural killer cells, can bind to Fc fragments of DSAs, trigger degranulation, and release lytic enzymes, which cause tissue injury and cell death.
The other mechanism is graft injury by direct activation of endothelial proliferation through increasing vascular endothelial growth factor production, up regulating fibroblast growth factor receptor, and increasing its ligand binding as well as other signaling pathways for cellular recruitment .
Complement fixing DSA s usually are against Class 1 HLA antigens , are seen early and damages the graft in a more aggressive way as compared to non complement binding DSA s which usually cause a smoldering process leading to TG.
Excellent, yes, a less severe and late form of graft damage.
ABMR (antibody-dependentacute or chronic) can occur due to complement-dependent and non-complement-dependent pathways upon binding of antibodies to mismatched donor antigens on the graft endothelium.
Non complement fixing DSAs can cause graft damage by 2 mechanisms either through antibody dependent cellular injury and/or direct endothelial damage
1-The innate immune cells, including neutrophils, macrophages, and natural killer cells, can bind to Fc fragments of DSAs, trigger degranulation, and release lytic enzymes, which cause tissue injury and cell death.
2-DSAs can cause graft injury by direct activation of endothelial proliferation through increasing vascular endothelial growth factor production, up regulating fibroblast growth factor receptor, and increasing its ligand binding as well as other signaling pathways for cellular recruitment.
Differences between Complement fixing and non-complement fixing Antibodies.
a]complement fixing Antibodies cause acute or acute accelerated AMR with abrupt deterioration of allograft function. Usually occurring within 6 months, antibodies are usually anti HLA class I, either IgG 1 or IgG 3 preformed Antibodies, causes {acute glomerular capillaritis and PTC capillaritis} with polymorphonuclear cells infiltration, C4d staining will be positive.
b] Non-complement fixing Antibodies cause chronic AMR , presented with gradual , subtle deterioration of allograft function with proteinuria which is often in nephrotic range occurring mostly after 6 months, usually De novo DSAs against HLA class II, C4d staining will be negative.
REFERENCES:
1-Zhang R. Donor-Specific Antibodies in Kidney Transplant Recipients. Clin J Am Soc Nephrol. 2018;13(1):182-192.
2- Prof.ahmad Halawa lecture
Excellent Batool
AMR causes parenchymal renal damage either by complement dependent pathway or non complement dependent pathway ,determined by the nature of concerned DSAs[complement fixing vs non complement fixing}.
Non complement fixing .
several mechanisms have been proposed for complement independent tissue injury induced by DSAs:
1] Activated monocytes and macrophages infiltrate to graft tissues.
2] FC receptor protein is found on the surface of several cells as B lymphoctes,Natural killer cells and macrophages.
3] Endothelial activation via mTOR signaling pathway.
4] Endothelial damage related release of IL 6.IL11 and IL8 would attract CD4 T cell involvement.
5] Antibody -cell dependent cytotoxicity: this is mediated through innate immunity {Natural killer cells and macrophages},which get activated by binding to FC region of DSAs.
6] Antigen -Antibody interaction on endothelial cells is also known to increase Von Willibrand Factor [VWF] with resultant platelets activation producing TTP like picture.
7] Antigen -Antibody interaction on endothelial cells would result in externalization of P-selectin molecules resulting in increased leukocytes trafficking
references:
1]Prof.ahmad Halawa lecture.
2]Chethan Puttarajappa,Ron Shapiro, Henkie P. Tan.Antobody -mediated rejection in Kidney transplantation:A review.Journal of transplantation.2012
Thank you for explaining the mechanisms, but how does it differ in presentation compared to complement-fixing?
Presentation of non Complement fixing is usually Chronic AMR with TG as the underlying pathology with chronic slow deterioration of allograft function in contrast to complement fixing AMR which is presenting as acute severe deterioration of allograft function.
Presence of DSA ( preformed or de novo) associated with high risk of ABMR, graft dysfunction & poor graft outcome.
DSA can cause graft injury through 2 mechanism:
(a): Antibody-dependent cellular cytotoxicity: through binding of neutrophil, macrophages, & NK cells to Fc fragment of DSA leading to degranulation of these cells & release of lytic enzymes causing tissue injury.
(b) Direct activation of endothelial proliferation via increasing VEGF production, up regulation of FGF receptors & its ligand binding, in addition to involvement of other signaling pathway of cellular recruitment.
References:
Zhang R. Donor-Specific Antibodies in Kidney Transplant Recipients. Clin J Am Soc Nephrol, 2018;12: 182-192.
What is the mechanism of the damage induced by complement non-fixing DSA?
1-DSAs can cause graft damage through antibody-dependent cellular cytotoxicity.
The innate immune cells, including neutrophils, macrophages, and natural killer cells, can bind to Fc fragments of DSAs, trigger degranulation, and release lytic enzymes, which cause tissue injury and cell death.
This process can mediate smoldering damages to the endothelial cells and is proposed as an important pathogenesis in subclinical and chronic antibody-mediated rejection phenotypes .
2- DSAs can cause graft injury by direct activation of endothelial proliferation through increasing vascular endothelial growth factor production, up regulating fibroblast growth factor receptor, and increasing its ligand binding as well as other signaling pathways for cellular recruitment .
This pathogenesis may contribute to transplant glomerulopathy and vasculopathy that feature vascular intimal thickness with smooth muscle cell invasion.
Referance ;
1. Valenzuela NM, Reed EF: Antibodies in transplantation: The ef fects of HLA and non-HLA antibody binding and mechanisms of
injury. Methods Mol Biol 1034: 41–70, 2013
2. Hidalgo LG, Sis B, Sellares J, Campbell PM, Mengel M, Einecke G,Chang J, Halloran PF: NK cell transcripts and NK cells in kidney biopsies from patients with donor-specific antibodies: Evidence for NK cell involvement in antibody mediated rejection .
Thank you for explaining the mechanisms, but how does it differ in presentation compared to complement-fixing?
1. What is the mechanism of the damage induced by complement non-fixing DSA?
Introduction
The diagnosis of AMR currently rests on circulating DSA, vascular injury, MVI & C4d.
However, 50% of AMR episodes are missed due to the lack of sensitivity of C4d staining.
Molecular endothelial-associated transcripts expressed in the grafts can also identify C4d negative AMR.
Endothelial activation & innate immune infiltration play a central role in graft injury by DSAs.
DSA is strongly associations with both AMR or graft loss.
HLA class I DSA appear early, while HLA II DSA occur late post-transplant & associates with chronic graft dysfunction.
Non-HLA antigens may also contribute to AMR.
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The mechanisms of antibody-mediated graft injury:
Acute AMR is mainly driven by the effector functions of the Fc fragment of HLA antibodies.
Fc-independent effects of antibodies cause chronic inflammation & proliferation.
Complement fixation also depends on antibody titer
& confounded by the presence of IgM.
HLA DSAs trigger CDC of target lymphocytes, however
endothelial cells (the primary target of antibody-mediated alloimmunity) are resistant to CDC in response to HLA antibodies.
Endothelial cells may upregulate cytoprotective factors & survival signaling to prevent HLA antibody induced cytotoxicity.
Complement fixing HLA I antibody augment basal P-selectin-mediated monocyte adhesion by binding to monocyte Fc gamma receptors (FcγRs).
DSA subclasses that interact with FcγRs elicit recruitment of monocytes, induce late phase adhesion molecules & synthesis of chemo-attractants & inflammatory cytokines that promote inflammation.
Complement fixing DSA carry a higher probability to develop AMR & progression to graft loss.
Cells recruited to the microvasculature in AMR are innate immune cells, NK cells & monocytes, which express FcγRs that allow for the recognition of DSA on the endothelial surface.
NK cells almost exclusively express Fc gamma receptor IIIA (FcγRIIIA), commonly known as CD16.
Patients expressing high-affinity variants of FcγRIIIA show more robust AMR responses in renal transplants.
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Complement-independent antibody-mediated endothelial & smooth muscle cell activation
HLA DSA acts as agonists to induce intracellular signals in endothelial & smooth muscle cells.
This is independent of the Fc fragment, & may be elicited by any IgG subclass.
Examples of such signals & their effects include:
– FAK (focal adhesion kinase): proliferation & migration of smooth muscle cells,
& thus contributing to the neointimal changes seen in chronic rejection.
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– MMP2 (matrix metalloproteinase-2) & nSMase2(neutral sphingomyelinase-2): HLA
I antibody-induced smooth muscle cell proliferation
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– Type 1 endothelial cell activation induces rapid & transient induction of
adhesion molecules & chemo-attractants
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— Type 2 activation requires protein synthesis resulting in chemokine &
adhesion molecule expression over hours to days.
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– HLA cross-linking trigger both type 1 & type 2 endothelial cell activation,
causing macrophage recruitment to the allograft during HLA antibody-
mediated injury.
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– Koenig et al. showed that when graft endothelial cells fail to provide an
inhibitory signal through expression of HLA class 1 molecules used to
educate recipient NK cells, NK cells are activated, leading to chronic vascular
rejection.
– This process of antibody-independent mechanism of NK cell activation is
known as “missing self” (MS).
– This focus on NK cells as primary architects of MVI, which may occur in the
presence of DSA or MS—both of which are independently detrimental to
allograft survival.
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– Valenzuela et al. showed that the worse graft outcomes were observed in
patients with complement-fixing DSA.
– A novel finding in this study was the presence of non-complement-fixing
DSA, the presence of MS shows a higher risk for graft loss in comparison
with MS negative organs. This confirms that MS can synergize with weak
DSA-mediated NK cell activation & translate into increased graft damage that
accelerates the development of chronic lesions (IF/TA).
– MS can more accurately predict the immunologic risk related to post-
transplant DSAs,& pre-transplant.
– Recipient killer cell Ig-like receptor typing might soon become the norm for
the prediction of MS between recipient NK cells & donor endothelium.
– DSA interpretation along with MS prediction does offer the potential to
improve the identification of pathogenic DSAs.
Conclusions
Vasculitis & MVI are promising markers of endothelial injury in AMR.
HLA antibody-induced endothelial cell inflammatory
activation may promote the MVI & innate immune infiltration characteristic of AMR.
Fc-mediated complement activation & engagement of Fc receptors act synergistically with endothelial activation to enhance inflammation & alloimmune damage.
References
1. Valenzuela et al. Antibody-Mediated Graft Injury: Complement-Dependent and Complement-Independent Mechanisms Curr Opin Organ Transplant. 2014 February ; 19(1): 33–40. doi:10.1097/MOT.0000000000000040.
2. L. Hidalgo : Missing Self and DSA—Synergy of Two NK Cell Activation Pathways in Kidney Transplantation J Am Soc Nephrol. 2021 Feb; 32(2): 262–264. doi: 10.1681/ASN.2020121731: 10.1681/ASN.2020121731
Thank you for explaining the mechanisms, but how does it differ in presentation compared to complement-fixing?