III. Clinical Relevance of HLA Antibody Monitoring after Kidney Transplantation
In your own words, summarise this article addressing the importance of DSA monitoring in transplantation practice.
In your own words, summarise this article addressing the importance of DSA monitoring in transplantation practice.
Dear All
Have you heard about de novo DSA?
What are the phenotypes of these DSA and how they affect graft survival?
Acute AMR occurs in about 6%of patients in early post-transplant period and this percent increases to 21%to 55% in patients who had detectable DSAs pre-transplant
preformed or de novo DSAs are associated with poor graft outcomes
weak pre transplant DSAs causes subtle type of graft damage causing delayed graft
function
for diagnosis of antibody mediated rejection
features of AMR in the biopsy together with the detection of circulating DSAs and evidence of antibody interaction with vascular endothelium must be present such as C4D positivity or micro-vascular inflammation
Risk factors for developing de novo DSAs
re-transplantation, HLA antibodies before transplantation, younger age (18-35 ) years,deceased donor transplantation , DR and DQ mismatch,non adherence , insufficient immunosuppression , infection and sub clinical T cell mediated rejection
de novo donor specific antibodies are more common than preformed antibodies and are associated with impairment in graft survival
lower graft survival are present more in whom are developed complement binding de novo antibodies compared to non complement binding
chronic AMR is found in patients who are non adherent to immunosuppression or in whom immunosuppression was reduced or withdrawn due to other causes as in calcinurin inhibitor free or steroid free protocols
patients who are at high risk for non adherence are ( younger adults who are in the transition from pediatric to adulthood services , psychiatric illness, substance abuse,insufficient socioeconomic support and adverse effects of immunosuppression)
studies showed more remarkable development of de novo DSAs in whom non adherent compared to adherent ones
Post-transplant screening of DSAs
is recommended for all patient groups in early post transplant period and this depend on pre transplant risk for AMR
No further testing is recommended during the first year, unless (i) there is a change in immunosuppression, non adherence is suspected, graft dysfunction occurs, or the patient is transferred to a remote outside center.
Beyond year one, no routine DSA monitoring is recommended for the four risk groups, except when one of the above mentioned four conditions occurs.
If DSA are present at any time, a biopsy should be performed, and if the biopsy result is positive, treatment of AMR is recommended.
Summary:
————–
Donor sepcific antibodies either preformed anti-HLA ab for both class1 and class2 or de-novo antibodies formation after transplantaion due to chronic microvascular inflammation and activation of the memory cells with out the need of costimulatory effect espcilay in case of nonadherence to immunosuppression or overreduction of immunsuppression by physician in case of infection and lead to ABMR ,both types associated with risk of acute antibody mediated rejection AMR early and late AMR more with de novo AB , another type of AB like non-HLA abs like MICA and ATR1 still there role in AMR post transplantion not clear and need more research .
the histological diagnosis of ABMR according the BANFF criteria 2013 depned on presence of C4D staining of the complemnet split products in PTCs with evidnece of microvascular inflammation in PTCS , glomerultitis, and circulating DSAs AB.
C4D negative AMR do exist in the presence of chronic endothelial injureies
C1 -q complement binding DSAs also found to be associated with higher rate of AMR and poor graft survival compared to non -complement binding DSA , some centres recommend the use C1q- assay as part of screening for DSAs after transplantion with conflecting results.
Montroing of denovo DSA sby L-SAB and according to some references even with lower cutoff values of MFI of 300 can impact the graft outcome, still nostandarziation among laberotreis its in the range of 1000-1500 ,also it dependes also on the phenotype of DSA like antiHLA -class11 AB carry higher risk of ABMR up to 60% of de novo DSA is of antiHLA class11 ( DR , DQ, ).
Risk factors forthe developmenet of dn-DSAs AB :
previous transplantation with preformed DSAs
young recipients pediatrics and adult up to 35 yreas ( drug nonadherences more )
Deceased donor
DR, DQ mismatches
under use of immunosuppressions , and poor compliance with immunsuppressions
Infections ( BKV ,CMV )
Subclinical TCMR .
monitroing of DSAs by using highly sensitive L-SAB assays as per TTS consnesus guideline:
-low risk group
in 3 -12 months time
-intermediate risk gruop ( history of DSAs ) , once in first month
no DSAs mintoring for the two above groups after the first year from transplant unless there is subtheraputic drug level with possible nonadherence IS , or change in the medications reduction by physician in case of infection malignancy or in case of transfere of the pateint to remote unit with longer fU intervales
– high risk and highly sensitizesd group :
Those with preformed DSAs , very high risk sensitized patients both need very close monitoring in the first week and first month , 3, intervaels and graft biopsy at 3 months even if negative still need close monitroing and repeat biopsy at any piont of undersuppression or acute graft dysfunction.
De novo anti-HLA DSA
These are antibodies that are not preexistent but develop after transplantation and are directed against foreign graft HLA. They are of 2 types:
phenotype 1: formed in the pre -sensitized patient EARLY post transplantation.
phenotype 2: formed in late post-transplantation in relation to recipient noncompliance.
Histological lesions are similar in the 2 phenotypes, graft survival is lower in case of de novo DSA.
Additional ABs sharing in the evolution of chronic AMR are MICA ABs, angiotensin II type 1 receptor activating ABs, and other anti -endothelial cells.
The most Important parameter in the diagnosis of ABMR is presence of circulating DSA In addition, evidence of AB interaction against the vascular endothelium should be there, either by C4d positivity or microvascular inflammation (peritubular capillaries and/or glomerulitis). Recently, presence of C4d-positivity in peritubular capillaries is no longer considered required for the diagnosis of AMR. In chronic AMR, C4d may often be negative. L-SAB-detected de novo DSA measured at the low positivity cut-off of 300 MFI is predictive of graft survival and others use higher cut-off of 1,000 MFI.
Risk factors for the development of de novo DSA:
Circulating HLA class II de novo DSA considered to be main cause for rejection. HLA class II mismatches (not only HLA-DR but also HLA-DQB, DQA, and DP) denote increased risk for late graft loss. Additional risk factors for the de novo development of DSA are younger age, deceased donor kidney transplantation, presence of HLA antibodies pre-transplantation, nonadherence to IS, and insufficient IS.
Infections, minor surgery, trauma, and acute TCMR episodes, often precede de novo DSA formation and AMR, even if being subclinical cellular rejection.
Guidelines for Post-transplant AB Monitoring:
-Posttransplant screening for DSA is recommended in the early postoperative period, timing of screening depends on the pre transplant immunologic risk.
– If DSA are present at any time, a biopsy should be performed, and treatment of AMR is recommended in case positive biopsy finding.
– Beyond year 1, routine DSA monitoring is not recommended except for some exceptions.
-Patients should be treated and monitored, if DSA are detected beyond 1 year.
the occurence of post transplant ab ( especially DSA AND THE COMLEMENT ACTIVATING Ab has imprtant role in the outcome of kidney transplantation .
DSA could be peristent , re emergent .or denovo the last one is most important one .
the role of AB againist mica ag, angiotensin type 2 receptor AB IS STIL TO BE DETERMINED .
DIAGNOSIS of AMR REQUIRES
1- serlogic evidence of DSA
2- fetures of Ab – endothelial injury .
3- features of tissue damage
risk factors for developing DSA
1- young age reciepient .
2- deceased donor
3- highly sensitized reciepient .
4- non adherence
5- inadequate immunsupression
6- inflamation
7- t cell mediated rejection .
8- DR, DQ mismatch .
9- retransplantation .
10- minor surgery .
DSA has negative impact on graft function particularly the denovo DSA Ab which is directed against class 2 HLA . ALSO THE COMPLEMENT ( c4d , c1) ACTIVATED DSA play an important role in AMR .
MONITORING
in * low * and * intermediate * DSA MONITORING IS NEEDED AT 3- 12 MONTH PERIOD.
IN *HIGH * and very high risk patient DSA and renal biopsy is needed .
especially in the following situation
1- if there is change in IS MEDICATION .
2- suspected non adherence
3-graft dysfunction
4-patient is transfered outside center .
Summary :
1- young age
2- deceased donor kidney.
3- early inflammatory events as infection, minor surgery and trauma.
4- HLA-class II mismatches, not only DR but also DQB, DQA,DP
Transplant society guidelines for post-transplant DSA monitoring :
1- non-adherence or changing immunosuppression.
2- graft loss.
3- patient transfer to a remote center.
( if DSA is +ve at any time, renal biopsy should be done and if +ve, treatment should
should be started as for AMR )
de novo DSA
mean donor specific antibody that formed after transplantation (after exposure to donor anti gene)
DSA responsible for AMR weather acute or chronic .
it may be found pre transplantation (sensitization) leading to DGF &poor allograft outcome.
and may formed after transplantation by stimulation of memory cll leading to formation of de novo AB.
&angiotensin 2 type1 receptor activating formation of new AB.
it become the most important parameter in the diagnosis of AMR.
previously diagnosis of AMR depend on detect 2 from 3
1-detect DSA
2-histological changes
3-c4d positive in peritubular capillaries
But in BANFF 2013 c4d not longer considered for diagnosis of ABR and now depend on 2 items only circulating DSA µvascular inflammation in kidney biopsy .
Luminex SAB assay detect low titer of circulating DSA even 300 MFI but in the diagnosis of AMR should be 1000MFI.
risk factors that develop de novo DSA:
-HLA specially type 2 mismatch
-younger age
-sensitized patient
-non adherence to immunosuppression
-insuffient immunosuppression
-cellular rejection episodes
Graft survival after detection of DSA
DSA against HLA class 2 associated with impaired graft survival (50% of patient lose their graft within 5 years of detecting DSA after transplantation)
in another study it increase risk of graft lose 10 fold.
C1q binding HLA AB (complement binding DSA)finding of this binding lead to 54%only survival graft compared to 94%survival in patient without it in cohort study between 2005-2011 on 1016 patient.
non adherence &reduction of immunosuppression lead to late graft lose.
As in free corticosteroid protocol ,recurrent infection, malignancy ,also convert CNI to m-tor .
Guidelines of transplantation society for DSA screening
1-in low risk group(not previously sensitized or DSA detection)screening of DSA from 3rd to 12 month after transplantation .
2-Intermediat risk group(previously detection of DSA but now free)start from 1st month& no further tests except if
*change immunosuppression
*non adherence to ttt
*graft dysfunction
3-High risk group(DSA detected)very high risk group (desensitized crossmatch positive)
*biopsy should done &if positive start ttt of AMR.
*DSA monitoring &biopsy during first 3 months
Finally
*HLA AB specially which binding to complement has high risk for AMR.
*luminex SAB play important role in DSA detection .
DSA Is associated with major cause of graft rejection(AMR).
Mainly two developments contributed to improve understanding of antibody-mediated
allograft injury:
(1) the recognition that deposition of the C4d (especially in peritubular capillaries of the
kidney allograft) may indicate antibody mediated allograft injury.
(2) DSA detected by highly sensitive techniques with inferior outcome of kidney transplants .
Recent investigations indicate that more than 60% of late kidney graft losses are due to
antibody-mediated humoral tissue injury.
Tissue injury caused by DSA:
AMR occurs in about 1 to 6% of patients, increase up to 21 to 55% in patients who had
detectable DSA already before transplantation and who received desensitization therapy .
Persistence or reemergence of DSA that were detectable already before transplantation
is associated with poor allograft outcome .Weak pretransplant DSA have been
associated with rather subtle types of graft damage, often leading to delayed graft
function .
early damage can later on translate into chronic (antibody mediated) changes.
During later phases of transplant after reduction of immunosuppresion and stimulation
of the memory cell response by inflammatory events can support the development of de
novo DSA against antigenic structures and result in failure of the transplanted organ due
to antibody-mediated organ injury. Additional antibodies that are discussed in the
evolution of chronic AMR are MICA antibody and
Angiotensin ll type 1receptor.
AMR:
Histological evidence of Amr ,
with the detection of a circulating DSA are required for the histological diagnosis of
antibody-mediated kidney graft rejection.
In addition, evidence of antibody interaction with the vascular endothelium must be
present, either by C4d positivity or microvascular inflammation (peritubular capillaries
and/or glomerulitis) .
Of note, in the latest update of the BANFF classification (BANFF 2013), detection of
C4d-positivity in peritubular capillaries is no longer considered a prerequisite for the
diagnosis of AMR.
Instead, moderte microvascular inflammation or even the demonstration of AMR-specific
gene transcripts together with circulating DSA is accepted as diagnostic criterions for the
diagnosis of AMR.
Luminex single antigen, improve detection of low levels DSA, ,which associate with
chronic graft survival.
Risk factors for donovo DSA
Retransplantation.
HLA antibodies before transplantation
Young age (18–35 years old) .
Deceased donor transplantation .
DR, DQ mismatch .
Nonadherence .
Insufficient immunosuppression .
Inflammation (i.e., infection).
Subclinical) T-cell-mediate.
DSA and graft survival:
a 10-fold increase in graft loss in patients who developed de novo DSA, with a 40%
lower graft survival rate 10 years after DSA .
de novo DSA, which made up 60% of all DSA and were directed against HLA class II
antigen mismatches of the donor, were associated with strongly impaired graft survival:
within 5 years from DSA detection, 50% of the patients in the study of Hidalgo lost their grafts.
Everly et al. reported on a 24% graft loss rate 3 years after de novo occurrence of DSA .
CIq binding HLA Antibodies A :
recent development is the introduction of solid-phase assays that allow the distinction of
complement-binding (C1q assay) or complement-activating (C4d assay) HLA antibodies
from HLA antibodies that do not bind or activate complement.
The 5-year graft survival rate in patients who developed complement-binding DSA (de
novo and persistent/reemerging) was 54%, strikingly lower than the 93% rate in patients
with DSA that were not complementbinding or the 94% rate in patients without any DSA.
The higher graft loss rate in patients with complement-binding DSA was attributable to a
higher rate of AMR, especially in the patients who developed complement-binding DSA
de novo after kidney transplantation.
Transplantation Society guide Tell Us about Posttransplant Antibody Monitoring?
(1) Posttransplant screening for DSA is recommended for all patient groups in the early
postoperative period, however, at different time points dependent on the pretransplant
risk of the patient for AMR.
(2) In “low risk” patients, who were not sensitized to HLA before transplantation and
who received their first allograft, the possible presence of DSA should be examined at
least once in the period from 3 to 12 months after transplantation.
(3) In “intermediate risk” patients, who were antibody-negative at the time of
transplantation but had DSA in previous testing, DSA should be examined already during
the first month.
No further testing is recommended for both groups during the first year unless:
(I) there is a change in immunosuppression,
(ii) nonadherence is suspected,
(iii) graft dysfunction occurs, or
(iv) the patient is transferred to a remote outside center.
(3) If DSA are present at any time, a biopsy should be performed, and if the positive
AMR is treated.
(4) “high risk” patients and in desensitized crossmatch-positive “very high risk” patients,
in addition to DSA monitoring ,biopsy is recommended. for all patients during the first 3
months after transplantation.
Even if the biopsy result is negative in these two groups but there are rapidly increasing
DSA or if the biopsy shows subclinical rejection, treatment of AMR should be initiated.
In the absence of AMR, DSA should be monitored and immunosuppression maintained
at higher levels.
(3) Beyond year one, no routine DSA monitoring is recommended for the four risk
groups, except when one of the above mentioned condition is there.
Antibody mediated rejection accounts for 1-6% of rejection episodes in the immediate post transplant cases. The incidence of AMR increases to 21 to 55% after few years after transplant. The main reason for long term graft loss was due to chronic antibody mediated rejection The risk of ABMR is more for those patients who had pre transplant high DSA and are associated with poor graft survival. Even weak pre transplant DSA levels have been shown to have mild graft damage that leads to sub clinical ABMR. This inturn lead to neoantigen exposure and formation of donor specific antibodies against other neo antigens which lead to chronic ABMR later. Many years after transplant, insufficient immunosuppression and non adherence to drugs stimulate the production of de-novo DSA which bring about the chronic rejection.
Diagnosis of ABMR traditionally involved the demonstration of C4d, a complement breakdown product in the peritubular capillaries and was called the footprint of ABMR. However in the later years and the recent Banff classification, C4d was not required as the criteria, instead DSA and endothelial gene transcripts that were demonstrated. Non HLA antibodies like anti ETR1,anti ATR1 Ab, anti VEC Ab, anti MICA Ab are usually associated with C4d negative ABMR. The Luminex assay to detect DSA could be negative in few patients where the circulatory levels of the antibody were too low or the complexes were deposited in the graft making it difficult to recognize by these assays. More sensitive Single Antigen bead DSA detect low levels DSA in these cases.
The risk factors for development of de Novo DSA are 2nd or 3rd transplantation, pre transplant DSA and sensitized state, younger age, deceased donor transplantation, HLA DR and DQ mismatches, Non adherence to immunosuppression, insufficient immunosuppression, recurrent infections and graft injury exposing the sub epithelial cryptic antigens.
Graft survival after development of de novo DSA is poor 50% graft loss in 5 years according to Hidalgo et al. Another study by Wiebe et al, demonstrated 40% graft loss in 10 years in those with de-novo DSA.
C1q binding De novo DSA also have been found to associated with overall poor graft survival. Many studies have published the role of HLA DR and DQ mismatches in relation to overall poor graft survival and have demonstrated the evolution of de novo DSA in these individuals.
Guidelines on DSA testing post transplant by Transplantation Society published in 2013
The immunosuppression should not be lowered for those patients with history of densensitization for high levels of DSA, as this would trigger the production of de Novo DSA and ABMR.
HLA antibodies are ;
Donor specific Abs (DSA) .
None donor specific (angiotensin 2 type 1receptor acivating Abs and endothelial cell Abs.
HLA Abs ,may present pretransplant or develop post transplant (de novo).
They may bind or activate the complement.
Risk factor for development of de novo DSA;
-Retransplantation
-HLA antibodies before transplantation
-Young age (18- 35)
-Deceased donor transplanation
-DR , DQ mismatched
-Nonadheerence
-Insuffient immunesuppression
-Inflammation or infection
-Subclinical T-cell mediated rejection
De novo DSA represent 60% of all DSA and are directed aganit HLA class 2 Ag mismatches of the donor and are associated with decrase graft survival and graft loss.
Complement-binding/activating de novo DSA denote the highest risk for AMR and graft loss.
Solid phase assay allow the distinction of complement binding(C1q assay) or activating (C4d assay ) from that do not bind or activate complement .
Post transplant Abs moitering ;
screening for DSA is recommended for all patient groups in the early post transplant period ,however,at different time points depend on the pre transplant risk of the patient for AMR.
Low risk patient; incuding patient not sensitized to HLA before transplantion and who received their first allograft .
DSA showed be examined at least once in the period from 3 -12 months after transplantion.
Intermediate risk paient ;iclude patient who are Abs negative at time of transplantation ,but had DSA in prevoius testing .
DSA showed de examined during the first month.
NO FURTHER TESTING IS RECOMMENDED FOR (LOW AND IINTERMediate GOUPS )DURING THE FIRST YEAR UNLESS;
-there is changein immunosupprssant
-nonadherence
-graft dysfunction
-patient is transferred to remote out side
If DSA are present at any time ,a biopsy showed be performed
Very high and High risk patient ;desestized crossmatched positive patient
In addition to DSA monitering .a biopsy is recommended for all patient during the first 3 months after transplantation.
Treatment showed be iniated if ;
-biopsy is positive
-biopsy is negative but there is rapidly increasing in DSA titre
– sub clinical AMR
In the absence of AMR ,DSA showed be moitered and immunosuppressant showed be maintained at higher level .
Beyond the first year post transplant ,no routine DSA monitering is recommended for all patient.
●In 1980 to 1990 ,after new immunosuppression strategies established, acute rejections after Tx decrease.
After that with intro to AMR ..
Chronic rejection expression was added
●WHAT IS THE MECHANISM OF AMR?
1. Cd4 complement deposition on peritubular capillaries and endothelial injuries which mediate AMR
2 DSA detected by immunoassay
Now by L .SAB .
●Tissue Damage Caused by Donor
1. HLA-Specific Antibodies:
DSA plays vital role in Acute rejection up to 50 % in pre transplantation DsA positive .
2 . DSA presence is a poor prognostic factor if present pretransplant
3. early damage by DSA can later on translate into chronic (antibody-
mediated) changes .
4 .
Other antibodies that are discussed in the evolution
of chronic AMR are MICA antibodies, angiotensin II type 1 and
receptor activating antibodies.
●Donor HLA-Specific Antibodies
Become the Most Important Parameter inthe Diagnosis of Antibody-Mediated KidneyAllograft Rejection :-
DSA is the diagnostic tool for of AMR not c4d .
●Risk Factors for the Development of (DeNovo) Donor HLA-Specific Antibodies:-
1 .HLA class II
mismatches (not only HLA-DR but also HLA-DQB, DQA,
and DP mismatches) confer an increased risk for late graft loss
2. younger age,
3.deceased donor kidneytransplantation,
4.presence ofHLA antibodies before transplantation,
5.nonadherence to immunosuppressive medication
●Graft Survival after Development of De
Novo Donor HLA-Specific Antibodies:-
1. De novo DSA, which made up 60% of all DSA were associated with strongly impaired graft survivaL within 5 years from DSA detection, 50% of the patients inthe study of Hidalgo lost their grafts.
●C1q-Binding HLA Antibodies:-
The higher graft loss rate in patients with complement-binding DSA was attributable to a higher rate of AMR, especially in the patients who developed complement-binding DSA de novo after kidney transplantation. Interestingly, pretransplant complement-binding DSA did not have the same predictive
values since about half of the patients lost these antibodies aftertransplantation.
●Nonadherence and Reduction of
Immunosuppression as Major Contributors to Late Graft Loss
1. Reasons for nonadherent to immunosuppressive medication or in whom immunosuppression was reduced
or withdrawn ?
to calcineurin-inhibitor-free or steroid-free immunosuppres-
sive protocols, recurrent infection, or malignancy
2. reduction of immunosuppression
by the physician may lead to adverse outcomes after kidney transplantation.
●Guidelines of theTransplantation Society (TTS) Tell Us about Posttransplant Antibody Monitoring?
1. Posttransplant screening for DSA
A. Low risk group
“low risk” patients, who were not
sensitized to HLA before transplantation and who received
their first allograft, the possible presence of DSA should be examined at least once in the period from 3 to 12 months after
transplantation.
B . “intermediate risk” patients, who were
antibody-negative at the time of transplantation but had DSA
in previous testing, DSA should be examined already during
the first month
C. “high risk” DSA-positive
D . “very high risk” patients, desensitized/ crossmatch-positive
●DSA monitoring in the previous C/D groups :-
a biopsy is recommended for all patients during the first 3 months after transplantation. Even if the biopsy result isnegative in these two groups but there are rapidly increasing DSA or if the biopsy shows subclinical rejection, treatment of AMR should be initiated. In the absence of AMR, DSA should be monitored and immunosuppression maintained at higher levels.
● de novo DSA ab not exsit before tx .
De Novo DS, appears after transplantation , also known as class II. You can still have DSA prior transplantation which is called class I. Other forms of DSA are ;
The presence of DSA specially De Nova HLA-Ab means poor graft survival.
1.Introduction ; Advances in immunosuppression resulted in significant reduction in T cell mediated rejection. How ever , anti-body mediated rejection defined as presence of C4d in the peritubular capillaries plus positive circulating DSA now become the major threat to graft survival in all solid organ transplantation(3-5)
2.Tissue damage caused by donor HLA- Specific Antibodies ; The presence of early DSA prior to transplantation is associated poor graft outcomes(9). Lately after transplantation, low levels of immunosuppression and inflammations are important factors which fuelling
the development of DSA and hence AMR. Non-HLA antibodies also plays a role in the pathogenesis of Chronic AMR e.g. MICA, angiotensin II receptor activating Ab, an other anti-endothelial cell antibodies. 3. Donor HLA-Specific Antibodies Become the most Important Parameter in the Diagnosis of AMR ; Diagnosis of AMR depends on; the presence of DSA, positive C4d in the peritubular capillaries or tubulitis and/or glomerulitis(14). According to BANFF 2013, C4d is no longer required , and the presence of AMR specific gene-transcripts plus DSA may be enough for making the diagnosis of AMR.
4.Risk Factors for the Development of De Novo Donor HLA-Specific Antibodies ; Re-transplantation(21), HLA-Ab prior to transplantation(16,21), Young age 18-35(16), Deceased Donor Transplantation(16), DR,DQ mismatch(16.21), Non-adherence(4,15), Insufficient immunosuppression(17), Inflammation or infection(18,19), Sub-clinical T cell mediated rejection(7,15)
5.Graft Survival after Development of De Novo Donor HLA-Specific Antibodies ; Many studies have demonstrated that appearance of DSA is strongly associated with poor graft survival (23),(15),(16).
6.C1-Binding HLA Ab ; Development of post-transplant complement-binding DSA is associated with impaired graft function(21). This in contrast to pre-transplant complement-binding DSA which usually disappears after transplantation.
7.Non-adherence and Reduction of Immunosuppressive therapy as Major Contributors to Graft Loss ; DSA was found in 60% of non-adherent patients compared to 20% in adherent patient(15). Reduction or minimisation of immunosuppressive therapy is bad because it is associated with AMR and poor graft survival. DSA was seen in23% of patients who were converted from Cyclosporine to everolimus compared to only 11% who remained on Cyclosporine.
8.What Do guidelines of the Transplantation Society(TTS) Tell us about the Post-transplant Antibody Mediated Monitoring ?
Conclusions ; L-SAB is important diagnostic tool for AMR. Both HLA and non-HLA Ab are associated with poor graft survival.
37% of patients who had a post-transplant (within 7-31 days) indication kidney biopsy had DSAs. 60% of these DSAs were denovo DSAs. 50% of patients lost their graft within 5 years after detection of DSAs.
Wiebe et al found 10 times increased risk of graft loss in those who developed denovo DSAs.
De novo DSAs were associated with 40% lower 10 year graft survival compared to those without Denovo DSAs.
Everly et al concluded that 24% graft loss rate 3 years after detection of Denovo DSAs.
Patients with graft loss showed higher incidence of DSAs and Non-DSAs than those without graft loss.
Loupy et al Study revealed that C1Q assay after transplantation was associated with adverse outcomes.
Non-adherence and reduced immunosuppression for chronic AMR. 60% of non-adherent patients developed DSA within 10 years compared to 20% in adherent patients.
Table 1 enumerate the risk factors for Denovo DSAs.
Conversion of immunosuppression is a risk factor for developing DSA as evidenced by a study where 23% (14/61) of post transplant patients who was converted from ciclosporine to everolimus compared to 11% (7/65) in those continued on ciclosporine..
TTS guidelines 2013 for post transplant DSA monitoring:
All patients at different time points depend on pre-transplant risk for AMR.
A/ during the first year:
1- Low risk patients: check DSA once in the first 3-12 months.
2- Intermediate risk: check DSA within first month. No further testing during the first year unless one of the following four: 1/ change in IS. 2/ suspected non adherence. 3/graft dysfunction. 4/ patient transferred to another center.
3- If DSAs are detected at anypoint of time, Biopsy should be done and AMT treatment is initiated.
4- High risk patients: check DSA and biopsy for all high risk patients within first 3 months. If +ve DSA, negative biopsy or subclinical rejection-àAMR treatment. If no AMR-àmonitor DSAs and keep high IS.
B/After first year:
No routine DSA monitoring except if there is one of the above mentioned four. Some experts suggested to monitor DSA once yearly to exclude AMR as early as possible. If DSA is detected at any point of time, manage as within first year.
de novo DSA
The antibodies that do not preexist but develop after transplantation and are directed against foreign graft HLA are considered as de novo anti-HLA DSA.
phenotype 1: developing in the presensitized patient early post transplantation.
phenotype 2: developing late post transplantation, mostly in relation to noncompliance.
Even if the histological lesions are similar in the 2 phenotypes, graft survival seems to be lower in case of dn DSA.
SUMMARY OF THE ARTICLE
Developments contributed to a better understanding of antibody-mediated allograft injury are :
Recent investigations indicate that more than 60% of late kidney graft losses are due to antibody-mediated humoral tissue injury, and there has been increasing evidence that HLA antibodies are responsible for graft losses not only in kidney but also in other solid organ transplantations .
Tissue Damage Caused by Donor HLA-Specific Antibodies
Donor HLA-Specific Antibodies are very Important Parameter in the Diagnosis of ABMR:
Risk Factors for the Development of (De Novo) Donor HLA-Specific Antibodies:
In brief ; Risk factors for the de novo development of DSA are :
Posttransplant Antibody Monitoring
According to the Guidelines of the Transplantation Society (TTS) 2013 :
(1) Post-transplant screening for DSA is recommended for all patient groups in the early postoperative period, however, at different time points dependent on the pretransplant risk of the patient for AMR.
(2) If DSA are present at any time, a biopsy should be performed, and if the biopsy result is positive, treatment of AMR is recommended.
(3) Beyond year one: no routine DSA monitoring is recommended for the four risk groups, except when one of the above mentioned four conditions occurs. Of note, a minority of members within the guidelines group supported HLA antibody monitoring at least once a year in all patients to rule out antibody-mediated allograft injury at its earliest stage.
(4) If DSA are detected beyond year 1, patients should be treated and monitored essentially as described above for the first year after transplantation.It needs to be mentioned that the consensus guidelines of TTS were published before Loupy and coworkers published their seminal paper on the impact of complement-binding HLA alloantibodies on kidney graft survival.
To diagnose antibody-mediated allograft injury we need the following
1–deposition of the complement split product C4d especially in peritubular capillaries of the kidney allograft may indicate antibodymediated allograft injury and
2– donor HLA-specific antibodies (DSA) detected by highly sensitive techniques with inferior outcome of kidney transplants
**Tissue Damage Caused by Donor HLA-Specific Antibodies
acute AMR occurs in about 1 to 6% of patients; however, this frequency may increase up to 21 to 55% in patients who had detectable DSA already before transplantation and who received desensitization therapy
Weak pretransplant DSA have been associated with rather subtle types of graft damage,often leading to delayed graft function
Insufficient immunosuppression lead to formation and stimulation of the memory cell response byi nflammatory events can support the development of de novo DSA against antigenic structures and result in failure of the transplanted organ due to antibody-mediated organ injury.
Other antibodies that are discussed in the evolution of chronic AMR are MICA antibodies, angiotensin II type 1 receptor activating antibodies, and other antiendothelial cell antibodies
**Donor HLA-Specific Antibodies Become the Most Important Parameter in the Diagnosis of Antibody-Mediated Kidney Allograft Rejection
detection of C4d-positivity in peritubular capillaries is no longer considered aprecondition for the diagnosis of AMR.
moderate microvascular inflammation or even the demonstration of AMR-specific gene transcripts together with circulating DSA is accepted as diagnostic criterions for the diagnosis of AMR.
in chronic AMR, C4d may often be negative (C4d-negative AMR). Before the introduction of highly sensitive antibody detection techniques, such as the Luminex single antigen bead (L-SAB) assay, there was often no DSA detectable in patients with chronic AMR due to the low levels of antibody.
**Risk Factors for the Development of (De Novo) Donor HLA-Specific Antibodies
circulating HLA class II de novo DSA are considered to be mainly responsible for rejection. T herefore,HLA class II mismatches (not only HLA-DR but also HLA-DQB, DQA, and DP mismatches)conferan increased risk for late graftl loss
Other risk factors for the de novo development of DSA and subsequent occurrence of (chronic) AMR are younger age, deceased donor kidney transplantation, presence of HLA antibodies before transplantation, non-adherence to immunosuppressive medication and insufficient immunosuppression or drug minimization
Even subclinical cellular rejection may lead to HLA antibody development with an increased risk for antibody-mediated allograft injury in subsequent years
**Graft Survival after Development of De Novo Donor HLA-Specific Antibodies
a 10-fold increase in graft loss in patients who developed de novo DSA, with a 40% lower graft survival rate 10 years after DSAdevelopment compared to patients without denovo DSA
Patients with graft loss showed a higher incidence of both DSA and non-DSA than patients without graft loss.
**C1q-Binding HLA Antibodies
We can use solid-phase assays to allow the distinction of complement-binding (C1q assay) or complement-activating (C4d assay) HLA antibodies from HLA antibodies that do not bind or activate complement.
The 5-year graft survival rate in patients who developed complement-binding DSA (de novo and persistent/reemerging) was 54%, strikingly lower than the 93%rateinpatientswithDSAthatwerenotcomplementbinding or the 94% rate in patients without any DSA. The higher graft loss rate in patients with complement-binding DSA was attributable to a higher rate of AMR, especially in the patients who developed complement-binding DSA de novoafterkidneytransplantation
**Non-adherence and Reduction of Immunosuppression as Major Contributors to Late Graft Loss
64% of graft losses in a selected patient cohort with indication biopsies were found attributable to (antibody-mediated) rejection Importantly, about half of the patients with rejection-associated graft loss were identified as non-adherent. de novo DSA were found to appear at a mean of 4.6 years after transplantation, and the prevalence of Denovo DSA after 10 years was 20% in adherent as compared to 60% in nonadherent graft recipients
Not only non adherence of the patient to immunosuppressive medication but also reduction of immunosuppression by the physician may lead to adverse outcomes after kidney transplantation
**What Do the Guidelines of the Transplantation Society (TTS) Tell Us about Posttransplant Antibody Monitoring?
1-Post-transplant screening for DSA is recommended for all patient groups in the early postoperative period
*low risk patients, who were not sensitized to HLA before transplantation and who received their first allograft, the possible presence of DSA should be examine once in period from3 to12months after transplantation.
*intermediate risk patients, who were antibody-negative at the time of transplantation but hadDSA in previous testing, DSA should be examined already during the first month.
*high risk patients and in desensitized crossmatch-positive
*very high risk patients, in addition to DSA monitoring, a biopsy is recommended for all patients during the first 3 months after transplantation.
2-If DSA are present at any time, a biopsy should be performed, and if the biopsy result is positive, treatment of AMR is recommended.
3-after year one, no routine DSA monitoring is recommended for the four risk groups, except when one of the above-mentioned four conditions occurs.
4-if DSA are detected beyond year 1, patients should be treated and monitored for the first year after transplantation.
In recent years the studies show that the acute & chronic AMR are increasing, in some of these studies the late graft failure is due to chronic AMR in 60% of patients, & found that HLA Abs are the responsible for this failure in all solid organ transplantation. Acute AMR occurs in 1-6% of renal transplant & this percentage increased to 21-55% in patients with pre transplant DSA detection especially in patients who receive desensitization regimen.
High level of DSA pre transplantation associated with poor graft survival while low level of DSA is associated with DGF. Early graft insult can progress to chronic changes result in endothelial injury leading to expression of new antigenic epitopes on transplanted tissues. These changes in association of insufficient immunosuppression & activation of memory cells can cause development of de novo DSA leading to graft loss. A study define de novo DSA as presence of DSA in transplanted patient serum only if pre transplant sera at time of transplant was negative (<300MFI) & there is no evidence of AMR in first 6 months of transplantation confirmed by protocol graft biopsy.
There are several risk factors contribute to development of DSA including:
It was found that graft loss is higher in patients with complement binding DSA than non complement binding DSA. All transplanted patients should be screen for the presence of DSA, but the time is different depending on patient pre transplant risk. In patients who are at low risk( non sensitized ) DSA screening done at least once in first 3-12 months of transplantation, while intermediate risk ( DSA negative at time of transplantation but had previous DSA positive result) the screen should be in first month post transplantation. High risk ( DSA +ve) & very high risk (desensitized crossmatch +ve ) patients need renal biopsy for all patients in first 3 months. More frequent monitoring of DSA required in :
There are 2 types of DSA, type I occurs in first 6 months post transplantation & it associated with rapid graft loss. Type II DSA occur after one year & it associated with chronic transplant glomerulopathy.
More than 60% of late renal graft losses are due to antibody-mediated humoral tissue injury that due to HLA antibodies.
-Tissue damage caused by donor HLA Specific antibodies
-Early after transplantation, acute antibody-mediated rejection (AMR) occurs in about 1-6% of patients, however, this frequency may increase up to 21-55% in patients who had detectable DSA already before transplantation and who received desensitization therapy.
-DSA before transplantation is associated with poor allograft outcome while weak pretransplant DSA leads to delayed graft function.
-After transplantation, insufficient immunosuppression and stimulation of the memory cell response by inflammatory events can support the development of de novo against antigenic structure lead to antibody-mediated injury.
Other antibodies involved in chronic AMR are MICA antibodies, angiotensin II type 1 receptor activating antibodies, and other antiendothelial cell antibodies.
-DSA is the most important parameter in the AMR.
-AMR is diagnosed by biopsy, DSA, in addition to positive C4d or microvascular inflammation but in the last BANFF 2013 classification detection of C4d –positivity in peritubular capillaries is no longer considered a prerequisite for diagnosis AMR.
-In chronic AMR, C4d may often be negative due to a low level of antibodies but now with the use of Luminex single-antigen bead can detect DSA with high sensitivity.
– In many patients with late antibody-mediated graft loss, even when HLA I alloantibodies are detectable, circulating HLA II de novo DSA are considered to be mainly responsible for rejection.
–
-Risk factors for the de novo development of DSA :
1.retransplantion.
2. HLA antibodies before transplantation.
3. young age (18-35)
4. Deceased donor transplantation
5. DR, DQ mismatch.
6. Nonadherence
7. Insufficient immunosuppression.
8. Inflammation
9. Subclinical T –cell-mediated rejection.
-There is reduced graft survival after the development of de novo DSA.
-The development of complement-binding DSA after transplantation was associated with adverse outcomes, AMR, and 5-year graft survival was lower than patients with DSA that weren’t complement binding or patients without DSA.
-Chronic AMR is found more frequently in the patient who is nonadherent to immunosuppressive medication, or whose immunosuppressive was reduced or withdrawn for other reasons.
-Guidelines for post-transplant antibodies monitoring :
1. posttransplant screening for DSA is recommended for all patient groups in the postoperative period depending on the pretransplant risk of the patient for AMR.
2. If DSA is present at any time, a biopsy should be performed, and if the biopsy result is the positive treatment of AMR is recommended.
3. Beyond year one, no routine DSA monitoring is recommended except for certain groups.
4. If DSA is detected beyond year one patient should be treated and monitored as described by the guideline.
De novo DSA developed by insufficient immunosuppression and stimulation of the memory cell response by inflammatory events against antigenic structures and result in failure of the transplantedorgan due to antibody-mediated organ injury.
Risk for development of de novo DSA :
• Retransplantation.
• HLA antibodies before transplantation.
• Young age ( 18- 35 y old).
• Deceased donor transplantation .
• DR, DQ mismatch .
•Non-adherence .
•Insufficient immunosuppression .
•Inflammation or infection.
•Subclinical T-cell-mediated rejection.
Now detected by L- SAB. with high sensitivity at low positivity.
• De novo DSA main responsible for late antibodies mediated graft loss.
• Patients with graft loss showed a higher incidence of both DSA and non-DSA than patients without graft loss.
• Increase incidence of AMR with de novo DSA complement binding which no have predictive value pre transplantation.
• For development of antibodies mediated allograft injury that :
***the recognition that deposition of the complement split product C4d (especially in peritubular capillaries of the kidney allograft) may indicate antibody mediated allograft injury .
***the association of donor HLA-specific antibodies (DSA) detected by highly sensitive
techniques with inferior outcome of kidney transplants. There’s also evidence that HLA antibodies are responsible for graft losses not only in kidney but also in other solid organ transplantations.
••• Increase incidence of AMR in patients who detected DSA pretransplantation and received desensitisation therapy and associated with poor graft outcome .
••• BANFF classification no longer consider positive cd+4 in pertibular capillaries for diagnosis of AMR. Luminex SAB now allows detection of denovo DSA with high sensitivity, can be measured at low positivity .
••• Denovo DSA is main responsible for late antibody mediated graft loss . HLA-DR b , HLA-DQB, DQA and DP mismatches confer an increased risk for late graft loss . Due to the strong linkage disequilibrium between
the DR and DQB or DQA but not DP gene loci, two DR mismatches often indeed represent 6 mismatches are relevant for induction of DSA.
Denovo DSA, which made up 60% of all DSA and
were directed against HLA class II antigen mismatches of the donor, were associated with strongly impaired graft survival within 5 years from DSA detection, 50% of the patients lost their grafts. Patients with graft loss showed a higher incidence of both DSA and non-DSA than patients without graft loss.
••• Solid-phase assays that allow the distinction of complement-binding (C1q assay) or complement-activating (C4d assay) HLA antibodies from HLA antibodies that do not bind or activate complement. Increased incidence of AMR WITH denovo DSA complement binding which not have same predictive value pretransplantation despite about half of the patients lost these antibodies
after transplantation.
••• Non adherents patients ( psychiatric disorders, substance abuse, and insufficient socioeconomic support) or others who with insufficient immunosuppressive for many causes either tapering , withdrawal or adverse effects intolerance associated with chronic AMR . Denovo DSA were found to appear at a mean of 4.6 years after transplantation, and the prevalence of de novo DSA after 10 years was 20% in adherent as compared to a remarkable 60% in nonadherent
graft recipients .
••• According to Transplantation Society Guidlines for posttransplant antibodies monitoring:
~ Post-transplant screening for DSA is recommended for all patient groups in the early postoperative period.
* According to pre-transplant risk for AMR:
i- low risk patients with no pretransplant of sensitisation to HLA should examine for DSA once from 3-12 month post transplant.
ii- intermediate risk patients with previous DSA examine in first month.
* Biopsy should performed if changes in immunosuppression, suspected nonadherence patients , DSA present at any times or patients transferred to remote outside Center, if biopsy positive AMR should received .
*** High risk patients who DSA positive or very high risk who previously desensitised crossmatch positive we must monitor DSA + biopsy 3 month after transplantation ,if the biopsy result is
negative in these two groups but there are rapidly increasing DSA or if the biopsy shows subclinical rejection, treatment of AMR should be initiated.
*The recognition of complement component C4d as a marker of Ab mediated allograft injury.
*The recognition of HLA DSA is associated with worse graft outcomes.
*Acute rejections eventually leads to chronic structural changes which leads to allograft loss.
*Diagnosis of ABMR requires evidence of circulating DSAs with micro vascular inflammation in biopsy , C4d detection , or recently AMR gene transcripts by molecular technologies .
*The new technology of Luminex with single Antigen bead detect DSAs with higher sensitivity.
*DSAs reduces markedly graft survival , especially if the DSAs has complement activating ability .
*Risk factors for development of Denovo-DSAs include :
Preformed DSAs:
– Deceased donor
-DR/DQ mismatches
-Younger age
-further transplantations
-Under immune-supression
-T cell mediated rejection
*High risk should be tested and biopsy should be taken for all patients in the first 3 months
Acute AMR that occurs early posttransplant has stronge relation with preexisting DSA before transplantation and who received desensitization all these will affect on graft survival and outcome also will cause delay graft function ,it’s known that early graft dysfunction or AMR both cause graft damage and this will cause poor graft function especially for those patients with insufficient immunosuppression also lead to inflammatory cells stimulation causing denova DSA formation.
Many methods are used to detect AMR like features in the graft biopsy of AMR and its Banff classification ,detection of C4d in peritubular capillaries also by using highly sensitive Ab detection techniques.
Risk factors that contribute to develop AMR or denovo DSA are:young patients, deceased donor,second transplant ,T cells mediated rejection ,infection and non adherence or immunosuppressive tapering.
Presense of denovo AMR affect mainly on graft survival and increase rate of graft loss due to its effect against HLA class II Ag mismatch of the donor and its consider the mani cause of developing AMR even in the presence of class I Ab .
All patients should be screened for DSA posttransplant but in different intervals depending on risk factors like pretransplant HLA sensitisation and history of transplantation which classify the patients into low risk ,intermediate risk ,high and very high risk groups .
The importance of AMR is increasing. In spite of successful control of acute T cell rejection AMR is sometimes uncontrollable. The presence of C4d in the graft and DSA detection by sensitive methods show AMR importance. There are increasing data that show HLA antibodies in form of DSA causing AMR and is associated with graft loss etiology in more than 60% of late graft losses detection of circulation DSA, C4d positivity or evidence of peritubular capillaries or glomerulitis could be made the diagnosis of AMR but there are C4d negative AMRs too. Nowadays result of Luminex single antigen bead (L-SAB) shows that even low titers de novo DSA are graft survival predictors. Known risk factors for de novo DSA are: younger age, deceased donor, DR mismatch, low-dose immunosuppression and inflammation in term of infection, trauma, and acute T cell rejections. De novo DSAs and non-DSAs can be predictors of graft survival. Complement binding DSAs were associated with higher rate of AMR especially when they were developed de novo and after transplantation. Chronic AMR was seen with high frequency in non-adherent patients to immunosuppression or when reduction of these medications was prescribed by their physician inappropriately. Insufficient immunosuppression such as conversion from cyclosporin to tacrolimus, especially when patients were steroid-free was associated with DSA and AMR and these patients should be screened for anti-HLA antibodies. If DSA were detected physicians should avoid to minimize immunosuppression. Transplantation Society consensus guideline recommends that DSA screening according to their pre-transplant risk should be performed. If DSA was detected biopsy is indicated and if it shows positive results, AMR treatment is recommended. In high risk group, protocol biopsy besides DSA screening is recommended and even subclinical AMR should be treated and high level immunosuppressive during first year should be maintained. After first year at least once in a year HLA Ab monitoring is supported.
☆ HLA antibodies and their association with AMR are the main topic in transplantation nowadays.
Detection of DSA is associated with poor outcomes in transplantation.
Antibodies mediated rejection is responsible for more than 60 % of the kidney graft failure.
☆ Acute AMR incidence significantly rise from 1-6% in all patients early after transplantation to 25% in patients with DSA before transplantation.
Weak pretransplant DSA is linked to delayed graft function.
Development of DSA (due to insufficient immunosuppressive and stimulation of memory cells) leads to antibody-mediated tissue damage and graft failure.
There are several antibodies that contribute to chronic AMR such as MICA AB, angiotensin II type I receptor activating antibodies and antiendothelial cell antibodies.
☆ Diagnosis of AMR is depended on detection of DSA with moderate microvascular inflammation in biopsy.
Detection of C4d positivity in peritubular capillaries is no longer acquired for AMR diagnosis since Banff 2013 classification.
Luminex-SAB is a sensitive tool to detect DSA even in low levels.
Weakly reactive de novo DSA detected by L-SAB at low positive level (cutoff of 300 MFI) is predictive of graft survival.
☆ Risk factors for DSA development and subsequent AMR are:
Retransplantation, HLA antibodies before transplantation, deceased donor transplantation, younger age (18-35 years), DR mismatch, non-adherence or insufficiency of immunosuppression, inflammation (infection, trauma, minor surgery) and subclinical T cell mediated rejection.
☆ De novo DSAs is account of 60% of all DSA and directed against HLA class II antigen mismatches. They are strongly associated with poor graft survival.
Hidalgo et al reported that 50% of patients lost their graft within 5 years from DSA detection.
Wiebe et al reported that a 10 fold increase in graft loss in patients with de novo DSA and 40% lower graft survival rate 10 years from DSA detection.
☆ Detection of complement-binding (C1q assay) and complement-activating (C4d assay) by solid phase immunoassays after transplantation are associated with poor outcomes (low graft survival, higher graft loss due to higher rate of AMR).
Pretransplant complement-binding DSAs nor have the same predictive values because 50% patients lost these antibodies after transplantation.
☆ Non-adherence and reduction of immunosuppression are the main contributing factors to chronic AMR and late graft loss.
Sellarés et al found that 50% of patients with rejection-associated graft loss were nonadherent.
Wiebe et al reported that prevalence of de novo DSA after 10 years after transplantation was 20% in adherent compared to 60% in nonadherent.
Risk factors for non-adherence are young adults in transition phase from pediatric to adult kidney services, previous non-adherence, psychiatric disorders, substance abuse, low socioeconomic status and side effects of immunosuppressive agents.
Patients with reduction or discontinuation of immunosuppressive drugs should be screened regularly for detection of HLA antibodies and antibody-mediated graft injury.
In patients with DSA, minimization of immunosuppression should be avoided.
————————–
☆ Guidelines of Transplantation Society
• Posttransplant screening of DSA is recommended for all patients in early postoperative periods.
• If DSA are present at any time, a biopsy should be performed.
• Beyond year one , no routine DSA monitoring is recommended.
• If DSA are detected beyond year one, patients should be treated and monitored essentially as for the first year after transplantation.
———
☆ Screening of DSA in :
• Low risk patients (not sensitized to HLA before transplantation and received first allograft) —-> at least once in period 3-12 months after transplantation.
• Intermediate risk (AB negative at time of transplantation but has DSA in previous testing) —-> during the first month.
• No further testing is recommended for both groups during the first year unless:
. Change of immunosuppression
. Non-adherence to immunosuppression
. Graft dysfunction
. Transfer of patient to remote center
It is important to recognize De novo antibodies formed later on after transplantation. these antibodies may appear 3-4 years even before failure. so recognition of them is crucial for early treatment. solid-phase assays are able to detect even low levels. as colleagues stated, deceased transplant, transplantation, and non-adherence to treatment are the main causes for the formation of such antibodies.
In case of high-risk monitoring of DSA and protocol biopsies are done in many centers over the first year follow-up.
acute AMR occurs in about 1 to 6% of patients; however, this frequency may increase up to 21 to 55% in patients who had detectable DSA already before transplantation and who received desensitization therapy .
How can we diagnose AMR?
biobsy is the gold standard together with the detection of a circulating DSA are required for the histological diagnosis of antibody-mediated kidney graft rejection. In addition, evidence of antibody interaction with the vascular endothelium must be present, either by C4d positivity or microvascular inflammation (peritubular capillaries and/or glomerulitis.
BANF classification , had removed cd4 positivity as acorner stone to diagnose amr(called Amr negative c4d)
luminax single antigen beads (L-SAB) had made a great difference in detecting circulating antibodies especially in chronic amr pt with very low titre antibodies.
what cause denovo dsa?
most studies realte denovo dsa formation to HLA DR mismatch ,another risk factors may increase formation of dsa,like youn recipent with prevoius transplant and has dsa befor with 6 mismatch and non complaint on treatmnet and has aprevoius episode of TCMR.
is garft survuaval afffcetd after developement oF DSA?
de novo DSA, which made up 60% of all DSA and were directed against HLA class II antigen mismatches of the donor, were associated with strongly impaired graft survival: within 5 years from DSA detection.
HOW CAN WE UNDERSATND LATE GRAFT LOSS,
antibody-mediated microcirculation injury is one of the leading causes of late graft loss, together with death with a functioning graft, recurrent renal disease, and interstitial fibrosis/tubular atrophy of unknown origin.
what are the causes of chronic amr ?
1-nonadherent to immunosuppressive medication , especially pediatric or adolescence.
2- whom immunosuppression was reduced or withdrawn for other reasons, for example, conversion to calcineurin-inhibitor-free or steroid-free immunosuppressive protocols,
3-recurrent infection, or malignancy .
4-non adherence due to psychiatric disorders, substance abuse, and insufficient socioeconomic support, but also adverse effects of immunosuppressive medication.
How can we monitor DSA after transplantion, recommend by TTS,
1-low risk” patients, who were not sensitized to HLA before transplantation and who received their first allograft, the possible presence of DSA should be examined at least once in the period from 3 to 12 months after transplantation.
2-intermediate risk” patients, who were antibody-negative at the time of transplantation but had DSA in previous testing, DSA should be examined already during the first month.
3-In DSA-positive “high risk” patients and in desensitized crossmatch-positive “very high risk” patients, in addition to DSA monitoring,a biopsy is recommended for all patients during the first 3 months after transplantation
Beyond year one, no routine DSA monitoring is recommended for the four risk groups
This review article speaks about impact of DSAs on longterm outcomes of renal allograft and suggest a follow up monitoring protocol
This review article speaks about impact of DSAs on longterm outcomes of renal allograft and suggest a follow up monitoring protocol after transplantation
After the development of immunosuppressive medications recently , the T cell mediated immune graft injury as been controlled , and the probleme of ABMR starts to appear
2 major developments have increased the understanding of the ABMR which are :
** the recognition of complement component C4d as a marker of Ab mediated allograft injury
** the recognition of HLA DSA , which is associated with worse graft outcomes
Early after transplantation, Incidence of AMR may reach up to 55% in patients with preformed DSAs who undergone desensitization before tx .
Acute rejections eventually causes chronic structural changes which leads to allograft loss
Lately after transplantation, suboptimal IS , memory t cells , inadherance may lead to denovo DSAs which also causes ABMR
Diagnosis of ABMR requires evidence of circulating DSAs with micro vascular inflammation in biopsy , C4d detection , or AMR gene transcripts by molecular technologies
Introduction of the highly sensitive techniques, Luminex with single Ag leads , enabled detection of DSAs with very high sensitivity
Risk factors for development of denovo DSAs include :
Younger age
2nd transplantation
Preformed DSAs
Deceased donor
DR/DQ mismatches
Nonadherance
Suboptimal IS , inflammation
T cell mediated rejection
DSAs whether preformed or denovo , reduces markedly graft survival , especially if the DSAs has complement activating ability ( as detected by C1q assays )
Studies have proved that non adherent patients or those with suboptimal IS due to various causes ( repated infections ,malignancies , are associated with chronic Ab mediated rejection with eventually leads to graft loss
For all the determintal effects of DSAs whether preformed or denovo , cause acute or chronic events , it was essential to adequately monitor patients for DSAs.
Transplantation society guide lines in post transplant DSA monitoring :
Low risk patients ,should be tested once through 3rd to 12th month post tx.
Intermediate risk should be tested in the 1st month
If DSAs was detected at any time renal biopsy should be done and managed accordingly
High risk should be tested and biopsy should be taken for all patients in 1st 3 month
Beyond 1 year no routin monitoring for DSAs except in certain conditions
The importance of AMR is increasing. In spite of successful control of acute T cell rejection AMR is sometimes uncontrollable. The presence of C4d in the graft and DSA detection by sensitive methods show AMR importance. There are increasing data that show HLA antibodies in form of DSA causing AMR and is associated with graft loss etiology in more than 60% of late graft losses detection of circulation DSA, C4d positivity or evidence of peritubular capillaries or glomerulitis could be made the diagnosis of AMR but there are C4d negative AMRs too. Nowadays result of Luminex single antigen bead (L-SAB) shows that even low titers de novo DSA are graft survival predictors. Known risk factors for de novo DSA are: younger age, deceased donor, DR mismatch, low-dose immunosuppression and inflammation in term of infection, trauma, and acute T cell rejections. De novo DSAs and non-DSAs can be predictors of graft survival. Complement binding DSAs were associated with higher rate of AMR especially when they were developed de novo and after transplantation. Chronic AMR was seen with high frequency in non-adherent patients to immunosuppression or when reduction of these medications was prescribed by their physician inappropriately. Insufficient immunosuppression such as conversion from cyclosporin to tacrolimus, especially when patients were steroid-free was associated with DSA and AMR and these patients should be screened for anti-HLA antibodies. If DSA were detected physicians should avoid to minimize immunosuppression. Transplantation Society consensus guideline recommends that DSA screening according to their pre-transplant risk should be performed. If DSA was detected biopsy is indicated and if it shows positive results, AMR treatment is recommended. In high risk group, protocol biopsy besides DSA screening is recommended and even subclinical AMR should be treated and high level immunosuppressive during first year should be maintained. After first year at least once in a year HLA Ab monitoring is supported.
Antibody mediated graft injury by DSA is an important cause of late graft loss.
Tissue damage caused be DSA:
Early after transplant, AMR is more frequent in patients with detectable DSA who received desensitization.
Persistence or reemergence of DSA (detected pre transplant) is associated with poor allograft outcome.
weak pre transplant DSA may lead to delayed graft function.
Role of DSA in diagnosis of AMR
Diagnosis of AMR require presence of features of AMR in biopsy with evidence of antibody reaction in vascular endothelium either by C4d positivity or microvascular inflammation (peritubular capillaries &/or glomerulitis) together with detection of circulating DSA.
In BANFF 2013, moderate microvascular inflammation or demonstration of AMR-specific gene transcript with circulating DSA are diagnostic for AMR, detection of C4d positivity is no longer needed for diagnosis of AMR.
Luminex single antigen bead (L-SAB) detect low levels of DSA with high sensitivity
A study showed that weakly reactive DSA measured at low positivity can predict graft survival
Risk factors for development of De novo DSA
Graft survival after development of De novo DSA
A study showed that De novo DSA (60% of detected DSA) were directed against HLA class II mismatches of the donor and were associated with increased risk of graft failure within 5 years from detection of DSA
Another study showed that patient who develop De novo DSA have increased risk of graft loss lower graft survival rate 10 years after DSA detection.
Patients developed complement binding DSA De novo after transplant have higher rate of graft loss and antibody mediated rejection.
Solid phase assay can differentiate between complement binding (C1q assay) and complement activating (C4d assay) HLA antibodies from HLA antibodies not bound or activated by complement
Non adherence and reduction of immunosuppression are major contributors to graft loss
Chronic AMR is more common in patients who are not adherent to immunosuppression or had reduction in immunosuppression due to infection or malignancy
Development of De novo DSA after 10 years was more prevalent in non adherent recipients
Insufficient immunosuppression is associated with significantly reduced graft survival in subsequent years
In patients with DSA, reduction of immunosuppression should be avoided.
Post transplantation antibody monitoring
Screening for DSA depends on pre transplant risk of development of AMR:
moderate & low risk patients:
High risk & very high risk patients:
After year one:
If DSA are detected after year one, patient should be treated and monitored as in the first year.
DSA whether de novo ,pre existing or recurrent, play major role in AMR. Presence of post transplant DSA has led to chronic AMR which is the cause in 60% of late graft loss cases.
They lead to tissue damage (the percentage increase from 1-6% to 21-55% if DSA are present pre-transplant even if desensitized. This end with DGF, chronic AMR and graft failure. Tissue damage will expose more antigens which , in the presence of low immunosuppressant concentration, may lead to de novo DSA.
AMR diagnosis require DSA presence by serology or tissue evidence of antibodies interaction with endothelium like C4d or moderate MVI. In chronic AMR C4d or DSA by old technique might be often negative. L SAB has high sensitivity in detecting DSA and hence chronic AMR even at low concentration (300 MFI)
risk factors for de novo DSA : HLA class II mismatches(DR,DQ , DP), 2 DR have higher risk , being young(18-35), deceased doner, pre transplant anti HLA, poor compliance or dose prescription, early infection or trauma, early cellular rejection
In the presence of de novo DSA ,the 5 year graft survival is reduced by 50% (Hidalgo study : anti class II),10 year graft survival was reduced by 10 fold ( Wiebe study) and 3 year graft loss 24%( Everly study). the sera of patients with graft loss has higher incidence od DSA and non DSA when compared with control group.
solid-phase assays provide a tool to differentiate between non complement dependent antibodies and complement dependent ( complement-binding :C1q assay ,or complement-activating :C4d assay)
positive C1q assay in post transplant (1,016 patients, by Loupy, )was associated with 5 year graft survival of 54% while it was 93% in those with non complement binding DSA and94% in those with no DSA. This was due to development of AMR
non adherence or poor prescription(Opelz et al ) in form of early withdrawal of CNI or steroid are associated with higher AMR or reduced graft survival .risk factors include patients who were at the transitional age if they got the graft at childhood, drug abuse, mental issues, lack of social support beside development of side effects.
50% of those who developed graft loss secondary to AMR were non compliant with their medications . Wiebe declared that de novo DSA appear at 4.6 year post transplant and are present in 20% of adherent patients 10 year post transplantation compared with 60% in non compliant.
Stopping or decreasing the doses of CNI or MMF after the first year post transplant was
associated with reduced graft survival later on (Opelz and D¨ohler ) and this will be more in patients who already have DSA(Wiebe). conversion to mTOR ended with23% DSA at 3-4.5 months . these results stressed the need for screening for antibodies and evidence of tissue injuries in those patients.
The Transplantation Society (TTS) in 2013 recommendations are :
1- screen for DSA for all patients early postoperatively . low risk(first transplant with no sensitization check once from 3-12 months after transplant, intermediate risk who had historic DSA in the first month . both are not re-tested unless graft dysfunction or the medications are interrupted or changed . no further tests are needed after one year unless indicated and the above instructions will be repeated.
2- high risk patients(DSA )or very high risk ( desensitized ) monitor DSA and do biopsy for all 1-3 months post transplant. If the titer is rising or there is subclinical tissue injury ,start treatment of AMR with keeping immunosuppressant at higher level . no further tests are needed after one year unless indicated and the above instructions will be repeated..
3- DSA presence should be followed by biopsy and starting treatment of AMR if proved.
This review gives a brief overview on the impact of DSA development on graft outcome in organ transplantation with a focus on risk factors for de novo alloantibody induction and guidelines for monitoring of DSA during the posttransplant phase.
The new era in immunosuppression medications led to a significant decrease in the occurrence of T-cell-mediated acute rejection episodes. Recent investigations indicate that more than 60% of late kidney graft losses are due to antibody-mediated humoral tissue injury, and there has been increasing evidence that HLA antibodies are responsible for graft losses.
Tissue Damage Caused by Donor HLA-Specific Antibodies:
Early after transplantation, acute AMR occurs in about 1 to 6% of patients; however, this frequency may increase up to 21 to 55% in patients who had detectable DSA already before transplantation and who received desensitization therapy. During later phases after transplantation, insufficient immunosuppression and stimulation of the memory cell response by inflammatory events can support the development of de novo DSA against antigenic structures and result in failure of the transplanted organ due to antibody-mediated organ injury.
Additional antibodies that are sharing in the evolution of chronic AMR are MICA antibodies, angiotensin II type 1 receptor activating antibodies, and other antiendothelial cells.
The Most Important Parameter in the Diagnosis of Antibody-Mediated Rejection is detection of a circulating DSA In addition, evidence of antibody interaction with the vascular endothelium must be present, either by C4d positivity or microvascular inflammation (peritubular capillaries and/or glomerulitis). The detection of C4d-positivity in peritubular capillaries is no longer considered a prerequisite for the diagnosis of AMR. In chronic AMR, C4d may often be negative (C4d-negative AMR). L-SAB-detected de novo DSA measured at the low positivity cut-off of 300 MFI is predictive of graft survival and some used the higher cut-off of 1,000 MFI.
Risk factors for the development of de novo DSA:
The circulating HLA class II de novo DSA considered to be mainly responsible for rejection. HLA class II mismatches (not only HLA-DR but also HLA-DQB, DQA, and DP mismatches) confer an increased risk for late graft loss. Additional risk factors for the de novo development of DSA are younger age, deceased donor kidney transplantation, presence of HLA antibodies before transplantation, nonadherence to immunosuppressive medication , and insufficient immunosuppression.
Infections, minor surgery, trauma, and early (acute) T-cell-mediated rejection episodes, often precede de novo DSA development and AMR, even if it is subclinical cellular rejection.
Guidelines for Posttransplant Antibody Monitoring:
1-Posttransplant screening for DSA is recommended for all patient groups in the early postoperative period, timing of screening depends on the pretransplant immunologic risk.
2- If DSA are present at any time, a biopsy should be performed, and if the biopsy result is positive, treatment of AMR is recommended.
3- Beyond year one, no routine DSA monitoring is recommended for the four risk groups, except for some exceptions.
4- If DSA are detected beyond year 1, patients should be treated and monitored.
This is very comprehensive replies, well done.
Thank you for mentioning the guidelines recommendations for Post-Transplant DSA monitoring. This is the main core of the question
HLA class II mismatch, which includes HLA-DQ and HLA-DR has been found to be a risk factor of de novo DSAs. In various studies, it has been demonstrated that HLA-DR and HLA-DQ mismatch are independent predictors of de novo DSA. Anti HLA-DP antibodies are less frequent than HLA-DR and HLA-DQ antibodies. HLA-DP antibodies are more common in re-transplanted patients and may be correlated with reduced allograft survival.
Excellent Esmat, well done
DSAs have a crucial role in kidney transplantation outcome.
Kidney transplant recipients who develop a de novo DSA after transplantation can present late-onset ABMR.
More than 60% of kidney graft losses are due to ABMR. Acute ABMR occurs in about 1-6% of patients and in about 20-55% of presensitized patients.
Persistence and reemergence of DSA that were detectable before the transplant is associated with poor allograft outcome, even weak pretransplant DSA associate with DGF. An early damage with injury to endothelial cells and expression of new epitopes can lead to chronic ABMR. Early inflammatory events (infection, surgery, trauma), early T cell mediated rejection and even subclinical, increase the risk of ABMR.
The type of DSA (preexisting or de novo) may be a predictor of worse outcomes in patients with ABMR. De novo DSA is mainly related to medication (conversion to CNI free or steroid free immunosuppressive protocols), non-adherence, inadequate immunosuppression, younger age, and deceased donor kidney transplantation, and has been associated with poorer outcome compared with preexisting DSA. Patients who have undergone reduction or discontinuation of immunosuppressive agents should be rigorously screened for occurrence of de novo DSA and ABMR.
DSA and histologic evidence such as C4d deposition or microvascular inflammation are required for diagnosis of ABMR. Although C4d positivity is no longer considered a prerequisite of ABMR. By using Luminex-SAB even a weak DSA can be detected and de novo DSA with MFI of about 300 is predictive of graft survival. HLA class II de novo DSAs are considered to be mainly responsible for late allograft loss even in the presence of HLA class I de novo antibodies.
Because of the strong linkage between HLA DR and DQA or DQB, two DR mismatches often represent 6 mismatches.
Discrimination between complement binding (C1q assay) or complement activating HLA antibodies with HLA antibodies do not bind or activate complement is possible now days with introduction of solid phase assays. De novo post-transplant complement binding HLA DSA are associated with higher graft loss compared to non-complement binding DSA.
Screening for DSA is recommended for all patients groups in the early postoperative period, but the frequency and timing of screening depends on the pretransplant risk of ABMR. In low risk patients (not sensitized and first allograft), they should be examined for DSA at least once in the period between 3-12 months after kidney transplantation. In intermediate risk patients (no DSA at the time of transplantation, previous history of presence of DSA), DSA should be examined during the first month. In high risk patients (DSA-positive) and very high risk patients (desensitized crossmatch positive) in addition to DSA examination, allograft biopsy is recommended during the first 3 months after kidney transplantation.
Excellent, well done.
AMR accounts for 60% of late kidney graft losses and there is increasing evidence that HLA antibodies are responsible for graft losses in kidney and other solid organ transplantation.
De novo DSA are Ab that are formed after transplantation and were not present before.
AMR can occure in up to 6% of recipients in early posttransplantation time but this percentage increases up to 55% with presence of DSA before transplantation and desensitization and it was associated with poor graft outcomes .
Chronic antibody-mediated rejection with its consequences on graft is thought to be due to endothelial injury with new antigenic epitopes are expressed on the surface of transplanted tissue.
Later after transplantation,insufficient immunosuppression and stimulation of the memory cell response by inflammatory events can support the development of de novo DSA against antigenic structures and result in failure of the transplanted organ due to antibody-mediated organ injury.
The latest update of the BANFF classification (BANFF 2013), detection of C4d-positivity in peritubular capillaries is no longer considered a prerequisite for the diagnosis of AMR.
moderate microvascular inflammation or even the demonstration of AMR-specific gene transcripts together with circulating DSA is accepted as diagnostic criterions for the diagnosis of AMR.
highly sensitive antibody detection techniques,as the Luminex single antigen L SAB allows the detection of DSA with high sensitivity.
While befor this technique DSA couldn’t be detected in chronic AMR and C4d might be negative in AMR.
Wiebeetal. reported that even weakly reactive, L-SAB-detected de novo DSA measured at the low positivity cut-off of 300 MFI is predictive of graft survival . Everly et al. confirmed this observation, with the exception that they used the highercut-off of 1,000MFI.
Risk Factors for the Development of (De Novo) Donor HLA-Specific Antibodies
circulating HLA class II de novo DSA are the main cause for rejection. Mainly HLA class II mismatches (not only HLA-DR but also HLA-DQB, DQA, and DP mismatches) increase risk for late graft loss .
Due to the strong linkage disequilibrium between the DR and DQB or DQA (but not DP) gene loci, two DR mismatches often indeed represent 6 mismatches that are relevant for induction of DSA.
Ab to DQ antigen is usually associated with chronic AMR and transplant glomerulopathy.
Additional risk factors for the de novo development of DSA and subsequent occurrence of (chronic) AMR are :
younger recipients.
deceased donor kidney transplantation.
presence of HLA antibodies before transplantation even with desensitization therapy.
nonadherence to immunosuppressive medication and insufficient immunosuppression or drug minimization.
early inflammatory events, as infections, minor surgery, trauma, and particularly early (acute) T-cell-mediated rejection episodes, often precede de novo DSA development and AMR.
De novo DSA was associated with poor graft survival in many studies particularly those against HLA class II mismatches .
HLA AB are found to be either complement binding or activating
complement-binding DSA (de novo and persistent/reemerging) was associated with lower graft survival patients with DSA that were not complement binding or patients without any DSA due to higher rate of AMR.
Chronic AMR is found more frequently in patients who are nonadherent to immunosuppressive medication or in whom immunosuppression was reduced or withdrawn for other reasons.
Nonadherant patient found to have higher percentage of De novo DSA with development of Chronic AMR and graft loss.
Nonadherence to immunosuppressive medication and insufficient immunosuppression does not only lead to the development of de novo DSA but has also significant impact when DSA already are present .
Wiebe et al. found nonadherence in 100% of patients with de novo DSA and acute graft dysfunction.
Guidelines for screening DSA post transplantation recommended screening for all patients at the early post transplant period & at different times according to pretransplant risk
low risk patient with no pretransplant DSA and first transplantation screened Once from 3-12 months post transplantation
For intermediate risk patients who were antibody-negative at the time of transplantation but had DSA in previous testing,
Examination during the first month
No further testing is required for both groups unless there is a change in immunosuppressant medication, non adherence, the patient transferred to a remote center.
If DSA is detected then biopsy should be done.
For high risk patients who are DSA-positive and in desensitized crossmatch-positive “very high risk” patients, in addition to DSA monitoring, graft biopsy for all patients at the first 3 months post transplantation.
Beyond 1 year , no monitoring required except when the previously mentioned conditions happened.
Excellent, well done.
Early postoperative DSA screening is indicated for all patient groups, depending on pretransplant AMR risk.
In “low risk” patients who had not been sensitized to HLA before transplantation and got their first allograft, DSA should be checked at least once in the 3-12 months after transplantation.
Patients with “intermediate risk” who were antibody-negative at transplant but had DSA before should be tested within the first month.
If immunosuppression is changed, nonadherence is detected, graft malfunction develops, or the patient is relocated to a distant facility, no additional testing is suggested for both groups during the first year.
To treat AMR if DSA is present, a biopsy should be conducted. In addition to DSA monitoring, in “very high risk” DSA-positive patients, desensitized crossmatch monitoring
All patients should get a biopsy within 3 months after transplantation.
It is important to treat AMR even if the biopsy results are negative in these two categories but there is a fast DSA increase or subclinical rejection.
Absent AMR, DSA should be evaluated and immunosuppression increased. After the first year, DSA monitoring is not suggested for the four risk categories, unless one of the four requirements is met.
A minority of the recommendations group members favoured HLA antibody surveillance once a year in all patients to rule out antibody-mediated allograft damage early on.
If DSA is diagnosed after year 1, patients should be treated and monitored as mentioned above.
AMR and graft loss are associated with HLA antibodies that are complement-binding/activating. However, recurrence of preexisting antibodies or the formation of de novo non-DSA may further raise graft loss risk.
Excellent, well done.
AMR is responasable for loss of around 60% of transplant grafts . Presence of DSA either preformed or do novo trigger humeral immune response causing graft injury and subsequent failure. AMR is characterized by presense of circulating DSA and histologically by deposition of C4D in microvascular structures .
The risk for developing preformed DSA includes previuos transplantation , blood transfusion and pregnancy , while de novo DSA are more common in case of previuos transplantation , younger recipient age (18-35) , deceased donor , Dr and DQ mismatch , presense of preformed Anti HLA Ab , infection , inflammation underimmunesuppression and subclinical T cell mediated rejection.
Transplantation Society guidelines recommend posttransplantation monitoring of DSA based on risk stratefications of the patient into :
1- Low risk patient ( who have their first transplantation and no Preformed DSA) : check DSA at least once after 3 to 12 month posttransplantation
2- Intermediate risk patients (who have pretransplantation DSA that were treated and was negative at time of transplantation : check DSA during the first month postoperative
If DSA were negative in the previuos patients , no need for rechecking the DSA again during the first year except if there is a change in graft function or immunesuppression or suspecting patient non compliance .
In case of positive DSA , biopsy should be performed and if reveal AMR , treat it .
3- In high risk sensitized patients : monitor by DSA and biopsy during the first 3 month postrtransplant .
After first year posttransplantion , no routine recommendation for DSA monitoring , but few authors recommend checking DSA at least once a year.
Excellent, well done.
Actually, we monitor the effect of DSA by monitoring graft function. Some DSA disappear with time.
De Novo DSA are antibodies that was not present before transplantation and became only developed postsensetization.
The management of de novo DSA is dependent on clinical syndrome. the tools used may include plasmapharesis sessions, IV immunoglobulin infusion, or Rituximab usage.
What are the phenotypes of these de novo DSA?
ClASS 1 OR CLASS 2?
De novo DSA may be either class I or II.
HLA antibody monitoring after transplantation
Tissue Damage caused by donor HLA specific antibodies
-AMR occurs 1-6% during early Tx but increases up to 21-55% who had DSA pre-Tx
-persistence/resurgence of DSA predicts poor graft survival
-MICA, antibodies, angiotensin 2 type 1 receptor activating and anti endothelial cell antibodies
DSA in diagnosing AMR
AMR- detection of DSA + HPE of AMR
BANFF 2013-moderate micro vascular inflammation or demonstration of AMR specific gene transcription + DSA is more relevant than C4d positivity in PTC
cAMR- may have negative C4d
LUMINEX SAB-high sensitivity to detect DSA
Wiebe et al
-even weakly positive L-SAB with cut off of 300 MFI predicts graft survival
Risk factor for the development of dDSA
1. HLA class 2 – not only HLA -DR but also HLA DQB , DQA and DP mismatches
-due to strong linkage disequilibrium between DR,DQB or DQA (not DP) gene loci, 2 DR mismatches represent 6 mismatches – induce DSA
2. Younger age (18-35)
3. Deceased donor kidney
4. Presence of HLA antibody before Tx
5. Non adherence to IS
6. Insufficient IS
7. Drug minimisation
8. Inflammatory conditions
9. Subclinical T cell rejection episodes
Graft Survival after Development of De Novo Donor HLA – specific Antibodies
Hidalgo et al
-DSA found in 37%
-dDSA-60% directed to all DSA and were directed against HLA 2 antigen mismatches of the donor – strongly associated with impaired graft survival: 5 year , 50% loss the graft
Wiebe et al
-10 fold increase in graft loss if dDSA
-40% lower graft survival rate in 10 years if DSA positive
Everlt et al
-24% graft loss rate at 3 years afte dDSA
C1q-binding HLA antibodies
Lousy et al- landmark trial showed that occurrence post transplantation of complement -binding DSA was associated with adverse outcome. 5 year graft survival rate -54% than DSA that were not complement binding (93%) or 94% without DSA
Higher AMR in those with complement binding DSA
But , pre-tranpalnt complement binding DSA- no predictive value as half of the patient lose those antibodies after transplantation
Non-adherence and reduction of immunosuppression as major contributors to late graft loss
Einecke et al 2009- antibody -medicated micro circulation injury -leading causes of late graft loss, death with functioning graft, recurrent renal disease, and interstitial fibrosis/tubular atrophy (of unknown origin)
Chronic AMR – non adherent to IS medication or in whom IS was reduced or withdrawn
High risk for non adherence
– Young age
– Psy disorders
– Substance abuse
– Insufficient socioeconomic support
– Adverse effect of meds
64% of graft losses due to AMR ( 50% of them non adherence to meds)
Wiebe et al – dDSA were found to appear at mean 4.6 years, after 10 year prevalence is 20%in adherent and 60% in non adherent
Opelz and Dohler et al 2008- insufficient IS as a major cause of graft loss, below certain level of IS significantly reduce graft survival
Patient with DSA – minimisation of IS should be avoided
Post Transplantation antibody monitoring
-recommended for all patient in the early postoperative period but at different timing
-low risk -no HLA sensitisation and first Tx- once at least once in the period from 3-12 months
-intermediate risk – antibody negative at the time if Tx but history of DSA – monitor DSA at 1 month
-no further test needed unless
-change in IS
-non adherence suspected
-graft dysfunction
-patient transferred to outside centre
-DSA present at any time- biopsy and start IS
-(high risk)DSA positive and desensitised XM positive ( very high risk)- DSA monitoring and biopsy first 3 month after Tx
-even if biopsy is negative but DSA increasing -AMR treatment should started
-beyond 1 year- no need DSA monitoring unless : change in IS, Nonadherence of IS, graft dysfunction or patient transferred to remote area
Excellent, well done.
This review article gives a brief summary of the impact of DSA on graft outcome, risk factors for de novo DSA formation and the guidelines for monitoring DSA post transplantation.
Early after transplantation, ABMR occure in 1 to 6% of patients, and this rate rises up to 21-55% in patients who had DSA pretransplantation & received desensitization therapy. The presence of DSA whether it is pre transplant or formed de novo post transplantation is associated with poor allograft out ome due to the risk of ABMR . De novo DSA which made up to 60%of DSA directed against class II HLA and considered the main cause of rejection( not only DR mismatch but HLA DQB, DQA and DP).
Risk factors for development of de novo DSA are:
Young age, deceased donor kidney transplantation, the presence of HLA ab before transplantation, non-adherence to immunosuppressive medications and insufficient immune suppression or drug minimization, retransplantation, DR, DQ mismatch, infection and subclinical T cell mediated rejection.
Complement binding DSA associated with lower graft survival rate than non complement binding , pretransplant complement binding DSA did not have the same prediction as about half of the patients lost these antibodies after transplantation.
Non adherence to medication lead to the development of de novo DSA in around 60% of the non adherent patients. Risk factors for non adherence are:
Young adults who are in transition from pediatric to adult care.
Psychiatric disorders
Substance abuse
Insufficient socioeconomic support
Adverse effects of immunosuppressive medications
Guidelines for screening DSA post transplantation recommended screening for all patients at the early post transplant period & at different times according to pre transplant risk
For low risk patient:
Once from 3-12 months post transplantation
For intermediate risk:
Examination during the first month
No further testing is required for both groups unless there is a change in immunosuppressant medication, non adherence, the patient transferred to a remote center
If DSA is detected then biopsy should be done.
For high risk patients:
DSA monitoring + graft biopsy for all patients at the first 3 months post transplantation.
Beyond 1 year , no monitoring required except when the previously mentioned conditions happened.
Have you heard about de novo DSA?
de novo DSA are the DSA which develop in a transplant recipient post-transplant
What are the phenotypes of these DSA and how they affect graft survival?
The phenotype of de-novo DSA induced AMR is different from that of pre-existing DSA associated AMR. (1)
de-novo DSA usually occur in the first year post transplant, can be class I or class II. Class I de novo DSA develop earlier, are associated with acute AMR and graft. Class II antibodies, especially DQ are the predominant ones, appear later and are usually associated with chronic AMR and transplant glomerulopathy. (2)
de-novo DSA associated AMR has poorer graft survival as compared to pre-existing DSA associated AMR (34% versus 63% at 8 years post rejection). (3)
References
1) Djamali A, Kaufman DB, Ellis TM, et al. Diagnosis and management of antibody-mediated rejection:current status and novel approaches. Am J Transpl 2014;14:255-271.
2) Valenzuela NM, Reed EF. Antibodies in transplantation: the effects of HLA and non-HLA binding and mechanisms of injury. Methods mol biol 2013;1034:41-70.
3) Aubert O, Loupy A, Hidalgo L, et al. Antibody-Mediated Rejection Due to Preexisting versus De Novo Donor-Specific Antibodies in Kidney Allograft Recipients. J Am Soc Nephrol 2017;28:1912-1923.
Well done Amit
“Class II antibodies, especially DQ are the predominant ones, appear later and are usually associated with chronic AMR and transplant glomerulopathy”
Antibody mediated graft rejection (AMR) is an important cause of graft loss. The presence of donor specific antibodies (DSA) is associated with poor graft prognosis. Early acute AMR is seen in 1-6% of transplant recipients, but the percentage increases to 21-55% in those with preexisting DSAs or who underwent desensitization. This early damage can later on progress to chronic graft dysfunction.
AMR diagnosis is on the basis of Banff criteria (presence of DSA and features of AMR on biopsy). Risk factors for de novo DSA formation include prior history of transplant, prior DSA presence, younger recipient, cadaveric donor, class II (DR, DQ) mismatch, inflammation (infection, trauma, minor surgery), early acute T cell mediated rejection, subclinical T cell mediated rejection, nonadherence and insufficient immunosuppression.
Circulating class II de novo DSA are the ones which are mainly responsible for AMR. Rates of graft loss are increased with presence of DSA with as high as 24%, and 50% at 3 year and 5 year after DSA detction. Graft loss increases by 10 times in presence of de novo DSA post transplant.
DSA may be complement activating (C4d) or complement binding (C1q). 5 year graft survival is only 54% with complement binding DSAs as compared to 93% with non-complement binding DSA and 94% without any DSA. Non-adherence is a very important risk factor for DSA formation. 64% of graft loss happens due to AMR out of which non-adherence accounts for 50% cases. The formation of de-novo DSA in non-adherent patient at 10 year post transplant is 3 times more than that in an adherent patient.
With such a high risk of graft loss associated with DSAs, post transplant DSA monitoring is an important step in transplant management. Guidelines recommend:
In low risk group (first transplant, no desensitization, no DSA pre transplant): Check DSA at least once in first 3 to 12 months post transplant.
In Intermediate risk group (DSA negative, but prior history of DSA presence): Check DSA in first month post transplant
If DSA is negative, no further testing is required in these 2 groups unless there is change in immunosuppression, graft dysfunction, non-adherence or if the patient is transferred to remote unit.
If DSA is positive, kidney biopsy is done and if it shows AMR, it should be treated.
In high risk group (DSA positive) and very high risk group (desensitized cross match positive), DSA testing with kidney biopsy should be done during first 3 months. If biopsy is negative, but DSA rising, then it should be treated as AMR. If no AMR in biopsy, monitor DSA.
After one year post transplant, routine DSA monitoring is not recommended except if there is change in immunosuppression, graft dysfunction, non-adherence or if the patient is transferred to remote unit.
But a recent paper (Crespo et al, Transplantation 2020) recommends DSA monitoring in low risk group at least once in 12 to 24 months and in other groups annually.
Have you heard about de novo DSA?
What are the phenotypes of these DSA and how they affect graft survival?
de novo DSAs are antibodies formed after renal transplantation and responsible for chronic graft dysfunction and chronic antibody mediated rejection.
multiple factors affect their formation like non compliance to immunosuppressive medications(drugs) ISDs and low dose of ISDs based on dose reduction in the late period post transplant, also presence of autoimmune antibodies, viral infection, and HLA mismatch.
DSA are IG subclasses, endothelial cell antibodies, angiotensin receptor antibodies
Hee-Yeon Jung, Su-Hee Kim, Min-Young Seo. Characteristics and Clinical Significance of De Novo Donor-Specific Anti-HLA Antibodies after Kidney Transplantation. J Korean Med Sci. 2018 Aug 20; 33(34): e217.
Dear Dr Ahmed,
Have you heard about de novo DSA?
Donor-specific antibodies (DSAs) can be classified according to the time of detection into a preformed DSA detected in the patient serum before transplantation and de novo DSA, which will be detected post-transplantation due to sensitization HLA antigens of the allograft. possible causes of de novo DSA formation is non-compliance, a trial of reducing the dose of immune suppressant by the treating team, inflammation and previous attacks of rejection (1, 2).
What are the phenotypes of these DSA and how they affect graft survival?
De novo DSAs against class I HLA antigens are usually detected early after transplant and usually IgG1 and IgG3 subclasses. They are associated with acute antibody-mediated rejection and early graft loss (2).
De novo DSAs against class II HLA antigens usually appear later and are commonly non-complement binding IgG2 or IgG4 subclass. They are persistent and associated with chronic antibody-mediated rejection and transplant glomerulopathy (2). The complement dependant and complement non-dependant allograft injury mechanisms were summarized in the attached diagram (2).
Additionally, another study that involved 125 recipients who had DSA detected in the first year had found an association between the DSA IgG subclass and the outcome. IgG3 dominant DSA was associated with a shorter time to rejection, increased microvascular injury, C4d capillary deposition, and graft failure. While IgG4 dominant DSA was associated with later allograft injury, increased allograft glomerulopathy, and interstitial fibrosis/tubular atrophy (IF/TA) (3).
References:
1) Arjang Djamali, and Daniel C Brennan. Kidney transplantation in adults: Prevention and treatment of antibody-mediated rejection of the renal allograft. © 2021 UpToDate. (Accessed on 17 November 2021).
2) Zhang R. Donor-Specific Antibodies in Kidney Transplant Recipients. Clin J Am Soc Nephrol. 2018 Jan 6;13(1):182-192.
3) 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.
Class II antibodies, especially DQ are the predominant ones, appear later and are usually associated with chronic AMR and transplant glomerulopathy (From Amit Sharma’s replies)
Recent investigations indicate that more than 60% of late kidney graft losses are due to antibody-mediated humoral tissue injury, and there has been increasing evidence that HLA antibodies are responsible for graft losses not only in kidney but also in other solid organ transplantations
Therefore, HLA antibodies and their association with AMR have become the main focus of research in organ transplantation
Tissue Damage Caused by Donor HLA-Specific Antibodies
Early after transplantation, acute AMR occurs in about 1 to 6% of patients; however, this frequency may increase up to 21 to 55% in patients who had detectable DSA already before transplantation and who received desensitization therapy [6–8]. Persistence or reemergence of DSA that were detectable already before transplantation is associated with poor allograft outcome.
Currently, features of AMR in the biopsy together with the detection of a circulating DSA are required for the histological diagnosis of antibody-mediated kidney graft rejection. In addition, evidence of antibody interaction with the vascular endothelium must be present, either by C4d positivity or microvascular inflammation
Risk Factors for the Development of (De Novo) Donor HLA-Specific Antibodies
circulating HLA class II de novo DSA are considered to be mainly responsible for rejection.
Therefore, most authors believe that specifically HLA class II mismatches (not only HLA-DR but also HLA-DQB, DQA, and DP mismatches) confer an increased risk for late graft loss
Due to the strong linkage disequilibrium between the DR and DQB or DQA (but not DP) gene loci, two DR mismatches often indeed represent 6 mismatches that are relevant for induction of DSA
Additional risk factors for the de novo development of DSA and subsequent occurrence
of (chronic) AMR are younger age, deceased donor kidney transplantation, presence of HLA antibodies before transplantation, nonadherence to immunosuppressive medication, and insufficient immunosuppression or drug minimization.
Most importantly, early inflammatory events, such as infections, minor surgery, trauma, and particularly early (acute) T-cell-mediated rejection episodes, often precede de novo DSA development and AMR [18–20]. Even subclinical cellular rejection may lead to HLA antibody development with an increased risk for antibody-mediated allograft injury in subsequent years
Graft Survival after Development of De Novo Donor HLA-Specific Antibodies
It leads to negative impact on graft survival
C1q-Binding HLA Antibodies
The 5-year graft survival rate in patients who developed complement-binding DSA (de novo
and persistent/reemerging) was 54%, strikingly lower than the 93% rate in patients with DSA that were not complement binding or the 94% rate in patients without any DSA.
Nonadherence and Reduction of Immunosuppression as Major Contributors to Late Graft Loss
Chronic AMR is found more frequently in patients who are nonadherent to immunosuppressive
medication or in whom immunosuppression was reduced or withdrawn for other reasons, for example, conversion to calcineurin-inhibitor-free or steroid-free immunosuppressive protocols, recurrent infection, or malignancy
What Do the Guidelines of the Transplantation Society (TTS) Tell Us about Posttransplant Antibody Monitoring?
(1) Posttransplant screening for DSA is recommended for all patient groups in the early postoperative period, however, at different time points dependent on the pretransplant risk of the patient for AMR.
a) In “low risk” patients, who were not sensitized to HLA before transplantation and who received their first allograft, the possible presence of DSA should be examined at least once in the period from 3 to 12 months after transplantation.
b) In “intermediate risk” patients, who were antibody-negative at the time of transplantation but had DSA in previous testing, DSA should be examined already during the first month.
No further testing is recommended for both groups during the first year, unless (i) there is a change in immunosuppression, (ii) nonadherence is suspected, (iii) graft dysfunction occurs, or (iv) the patient is transferred to a remote outside center.
(2) If DSA are present at any time, a biopsy should be performed, and if the biopsy result is positive, treatment of AMR is recommended. In DSA-positive “high risk” patients and in desensitized crossmatch-positive “very high risk” patients, in addition to DSA monitoring, a biopsy is recommended for all patients during the first 3 months after transplantation. Even if the biopsy result is negative in these two groups but there are rapidly increasing DSA or if the biopsy shows subclinical rejection, treatment of AMR should be initiated.
In the absence of AMR, DSA should be monitored and immunosuppression maintained at higher
levels.
(3) Beyond year one, no routine DSA monitoring is recommended for the four risk groups, except when one of the above mentioned four conditions occurs. Of note, a
minority of members within the guidelines group supported HLA antibody monitoring at least once a year in all patients to rule out antibody-mediated allograft injury at its earliest stage.
(4) If DSA are detected beyond year 1, patients should be treated and monitored essentially as described above for the first year after transplantation.
Antibody mediated rejection became understandable when the deposition of the complement split product C4d and donor HLA-specific antibodies (DSA) were recognised as both correlated with poor outcome of kidney transplants
-Tissue Damage Caused by Donor HLA-Specific Antibodies
The presence of DSA either before or after transplantion indicates poor prognosis of the allograft.Antibody-mediated organ injury can occur later in transplantation process due to emerging of denovo DSA caused by inadequate immunosuppression and stimulation of the memory cell response. Chronic Antibody mediated rejection is caused by MICA antibodies, angiotensin II type 1 receptor activating antibodies, and other antiendothelial cell antibodies
-Donor Specific Antibodies are the Most Important Parameter in the Diagnosis of Antibody-Mediated Kidney Allograft Rejection
In order to diagnose AMR in the biopsy DSA , C 4d in peritubular capillaries and microvascular inflammation need to be detected.Om the other hand BNF 2013 stated that is not mandatory to detect C4d to diagnose AMR . Meanwhile microvascular inflammation or AMR-specific gene transcripts and DSA is considered diagnostic for diagnosing AMR.Luminex SAB technique is highly sensitive in detection of DSA
-Risk Factors for the Development of (De Novo) DSA
Includes HLA type II mismatch, younger age, deceased donor kidneys, HLA antibodies before transplantation, inappropriate use or dose of immunosuppressive therapy and inflammatory events.
– Graft Survival after Development of De Novo DSA
In a study byHidalgo et al. de novo DSA, represented 60% of all DSA and it was directed against HLA class II antigen mismatches of the donor, this found to have positive correlation with impaired graft survival.
-C1q-Binding HLA Antibodies
The incidence of graft loss was higher in patients with complement-binding DSA due to a higher rate of AMR, particularly in those who developed complement-binding DSA de novo after transplantation.
-Late Graft Loss is mainly attributed to nonadherence and Reduction of Immunosuppression.
– Transplantation Society (TTS) guidelines about Posttransplant Antibody Monitoring
· Screening for DSA during post transplantation period
· DSA presence , neccesistate biopsy taking
· No need for routinely DSA monitoring after 1 year with exceptions. Some adviced to monitor HLA antibody at least once a year in all patients.
· If DSA are detected after 1 year , patients should be treated and monitored for the first year after transplantation
Over the past few decades, with the discovery of new immunosuppressive therapies directed mainly against T lymphocyte-mediated immune response, the incidence of acute cellular rejection has declined markedly. In addition to careful HLA typing, adequate matching, screening for DSAs and identification of ABO compatibility, hyper-acute and acute antibody mediated rejection has been eliminated to great extent. But some patients with kidney transplantation, in the era of potent immunosuppression, are still losing their graft lately because of antibody mediated rejection. Antibody mediated rejection is defined based on the histologic evidence of complement mediated injury characterized by detection of C4d in the peritubular capillaries and also detection of circulating DSAs. So if both criteria are present, antibody mediated rejection is confirmed.
DSAs could be preformed, in the pretransplantation period, or de novo formed after kidney transplantation.
The appearance of de novo DSAs over time is variable and dependent on several risk factors: retransplantation, HLA antibodies before transplantation, young age (18–35 years old), deceased donor transplantation, DR, DQ mismatch, nonadherence, Insufficient immunosuppression, Inflammation or infection, intraindividual variability of immunosuppressant levels, cutoff of medium fluorescence intensity (to define DSAs( 1000-1500) based on laboratory definition.
Acute antibody mediated damage can cause chronic changes, most likely because endothelial injury and new antigenic epitopes expressionon the surface of transplanted tissue. Lately after transplantation, insufficient immunosuppression and stimulation of the memory cell response by inflammatory events can induce activation formation de novo DSA against kidney graft.
Additional antibodies against non-HLA antigens can also produce chronic AMR . Examples include MICA antibodies, angiotensin II type 1 receptor activating antibodies, and other antiendothelial cell antibodies.
Relationship between DSA detection and AMR is poorly described. In some patients, AMR proves to be concurrent with DSA detection, but in others, AMR develops over time.
DSA monitoring should be performed based on recipient’s immunological stratification.
Low: No anti-HLA antibodies, no sensitizing events, and first RT.
Medium: Anti-HLA antibodies (panel reactive antibodies, calculated by the most sensitive technique available < 80,<80%) with previous sensitizing events but no DSAs, re-RT, DR-DQ incompatibility, or acute rejection> with previous sensitizing events but no DSAs, re-RT, DR-DQ incompatibility, or acute rejection.
The patient’s immune risk should be stratified before deciding on the DSA monitoring regimen.
High: Anti-HLA antibodies (>80%) with DSA levels detected pre-RT.
In low risk patients as defined above, the possible presence of DSA should be examined at least once in the period from 3 to 12 months after transplantation which is compatible with the recommendation by Spanish panel requesting at least 1 DSA determination between 3 and 12 month post-RT in all patients.
In intermediate risk patients, DSA should be examined already during the first month. No further testing is recommended during the first year, unless (i) there is a change in immunosuppression, (ii) nonadherence is suspected, (iii) graft dysfunction occurs, or (iv) the patient is transferred to a remote outside center. Graft biopsy should be performed whenever DSA are present , and if the biopsy result is positive, treatment of AMR is recommended.
In high risk patients a biopsy is recommended for all patients during the first 3 months after transplantation in addition to DSAs level. If the biopsy result is negative and DSA or if the biopsy shows subclinical rejection, treatment of AMR should be initiated. In the absence of AMR, DSA should be monitored and immunosuppression maintained at higher levels.
ABMR is the most common cause of graft failure, constituting 64% of the causes of graft loss and detection of DSA is associated with 40 % lower graft survival at 10 years after appearance of DSA and 10 fold increase in risk of graft loss.
Complement binding DSA are associated with significantly lower graft survival than non complement binding DSA
Incidence of occurrence of early ABMR is markedly increased in patient with preformed DSA and those who received desensitization and that affect graft survival.
Diagnosis of ABMR :
⦁ Histologic evidence of acute tissue injury (capillaritis and/or glomerulitis)
⦁ Evidence of antibody interaction with vascular endothelium (C4d staining in peritubular capillaries [PTCs])
⦁ Serologic evidence of circulating DSAs
If the patient has first criteria and only one of the other 2 criteria, the patient is considered to have ABMR, this means C4d staining can replace DSA, and C4d negative ABMR exists (ABMR without activation of complement cascade)
DSA best detected by Luminex which can detect very week DSA with MFI of 300
Risk factors for developing denovo DSA
1. HLA mismatch especially class II (DR, DQB, DRQA, DP), 2HLA-DR mismatch is associated with poor graft and patient survival this is because of linkage disequilibrium between DR and DQ alleles so 2 DR mismatch means 6 class II mismatch
2. Presence of preformed DSA before transplantation
3. Younger age
4. Non living related (deceased) donor kidney
5. Planned subtherapeutic immunosuppression (due to malignancy, infection) or conversion to CNI free or CS free protocols
6. Non compliance on immunosuppressive medication ( very significant risk factor)
7. Inflammation induced by infections, surgery or TCMR
8. Other factors including psychiatric disorders and substance abuse
Monitoring of DSA
DSA should be monitored once in early post transplant period (first 3 month) in all patients
After first 3 month no further testing is required except in the following situations
⦁ Patients who has received desensitization to render cross match negative (only for first 1 year post transplant)
⦁ Modification of immunosuppression
⦁ Suspicion of non adherence
⦁ Graft dysfunction
⦁ Transfer of the patient to another center
Some recommend assement of DSA annually
Indications of renal biopsy
1- All patients with detectable DSA
2- Patients who receive desensitization protocol biopsy should be done in the first 3 m post transplant regardless of DSA
Indications for treatment of ABMR
1- Presence of DSA together with histologic features of ABMR
2- Rapid increase of DSA with normal or near normal biopsy in in patients who received desensitization to render cross match negative
Dear All, please respond to the question and emphasize the clinical importance of Post-transplant monitoring of DSA.
Please, check this very recent Evidence-based Expert Paper from Transplantation: August 2020 – Volume 104 – Issue 8S2 – p S1-S12
DOI: 10.1097/TP.0000000000003270
De Novo DSA monitoring and management IS
This article designed to establish recommendation for DSA monitoring and its correlation with IS therapy. The paper has 2 sections : monitoring the DSA and methods to be taken if DSA present.
Monitoring DSA
1. Immunological risk
• Characteristic of each patient is important to take into consideration as different DSA types confer different level of risk
• Common anti -HLA antibodies are class 2 – mainly anti-DQ followed by DR
• Isolated anti HLA antibodies towards class 1 is rare
• Temporal relationship between DSA and AMR is poorly described
Low- No anti -HLA antibodies, no sensitising events and first RT
Medium: Anti-HLA antibodies (PRA,CPRA 80% with DSA level detected pre-RT
2. Recommended at least 1 DSA determination between 3-12 months in ALL
3. Subsequent monitoring
-low risk with normal renal function – every 12-24months
-medium and high risk with normal renal function – monitor every 12 months
4. Monitoring frequency should be according to patients clinical indication
5. DSA should be performed if:
a. Significant change in IS (minimisation/suspension/conversion)
b. Significant variability of CNI drug levels(esp tacrolimus
c. Poor adherence to IS is suspected
d. Graft dysfunction ( increased creat/ proteinuria)
At least one antibody determination with solid phase techniques -Luminex platform
6. dDSA positivity should be correlated with clinical situation
7. dDSA positive patient should be evaluated for adherence to meds
8. dDSA positive patients should be monitored closely
9. dDSA positive patient should be regarded as high risk
10. dDSA positive should guide the management of IS- increase the IS
11. dDSA positive should have renal biopsy done if feasible
Management of DSAs
1. objective is to prevent recurrence according to risk factors –
a. young age,
b. female gender,
c. presence of pre-Tx antibodies other than DSA,
d. larger number of HLA mismatch -DR,DQ,
e. re-RTx or other sensitising events like transfusions or pregnancies
f. early T cell mediated rejections
g. noon-adherence to meds
h. intraindividual variability of IS levels
i. stopping or minimisation of IS dosage
j. stopping/ reduction of CNI dosage
k. use of mTOR without CNI
2. minimise tacrolimus variability – variability >30% increase risk of DSA development
a. oral variability is low ( 25% on average) with high intrapatient variability (5-90%)
b. once a day dose increases adherence and variability
c. factors affecting variability – diarrhoea , vomiting, anaemia , hypoalbuminemia, diet, drugs that interacts , pregnancy
3. minimisation of tacrolimus dosage in combination with MPA should be avoided to prevent DSA occurrence
a. evidence from studies
i. tac level ,8mg/dL during first year associated with increased risk of dDSA and chive hum oral rejection at 1 year, increased risk of graft loss at 5year
ii. tacrolimus level <5ng/dL have been stated to be associated with graft loss
iii. another – tac level between 6.4-6.4 at 1 and 3 year improved graft survival compared to standard dose CyA or low dose sirolimus
iv. 2 RCTs comparing CyA,MPA and steroids vs CyA convert to everolimus without steroids- evero and without steroid had higher risk dDSA and AMR
4. Improve adherence by education and use less frequency drugs
Pharmacological Management
1. IS treatment based on patient profile
2. When developed dDSA,
a. Normal kidney function and normal biopsy -not lowering IS
b. Normal kidney function and microinflammation in biopsy – optimise the IS
c. Cannot perform biopsy- do not reduce the IS, some might need incrementin IS
d. Acute dysfunction – combination of PLEX or IA or polyclonal gamma globulin with or without rituximab
e. Proteinuria or subclinical /chronic renal function impairment – optimising IS and introduce RAAS
Several SLRs showed that IA with protein A or PLEX- decrease DSA levels and improve histological renal function
Use of Rituximab is controversial -combination with other therapies – generally positive effect
• RCT with 40 patients combining PLEX as well as IvIg and steroids – RTX did not have added benefit at 1 year
• cAMR – given RTX- no added benefit at 1 year
Bortezumab vs placebo- no differences but more ADR
Ecuzimab -may stabilise kidney function with ACEI
Toclizumab -may improve graft function at 2 year
To summarize the take-home message of this paper in points:
· The introduction of potent immune-suppressive medications has dramatically decreased the incidence of acute T-cell mediated rejection. However, this revealed the significant impact of DAS and antibody-mediated rejection (ABMR) on long term allograft outcomes.
· The incidence of acute ABMR is about 1-6% of cases in the first few months post-transplantation. However, the percentage will increase up to 55% in patients who have detectable DSA pretransplantation.
· Even very low levels of DAS (detected by Luminex single antigen bead [L-SAB] at a cut-off of 300 MFI) has a prognostic impact on allograft survival.
· The circulating HLA class II DSA has a much more significant influence on graft survival than class I.
· The recognized risk factors for the development of de novo DSA with subsequent ABMR and graft loss include young recipient, deceased donor kidney, pre-existing DSA, non-compliance, a trial of reducing the dose of immune suppressant by the treating team, inflammation and previous attacks of rejection.
· Based on the abovementioned points, it was recommended to screen for DSA in the following scenarios: 1) early post-transplantation for all patients. There is no need to be repeated if the patient is negative for DSA and at low immunological risk. 2) testing the recipient for DSA is recommended whenever there is suspicion of non-compliance, unexplained allograft dysfunction or trial of lowering the immune suppression.
· Once de novo DSA is detected, a kidney biopsy should be taken, and if there are histological findings suggestive of ABMR, the treatment of rejection should be started immediately.
· In high-risk recipients, even if the biopsy result is not diagnostic for rejection but he has a significantly rising DSA titre, the treatment of ABMR should be started.
The induction and maintenance of immunosuppression drugs (ISD) in renal transplantation of course improve graft survival and decrease incidence of cellular and humoral rejection.
In addition, chronic rejection is evident especially antibody mediated rejection which characterized by deposition of peritubular c4d in the graft and circulating donor specific antibody.
Presence of detectable DSA pretransplant was associated with 20-50 % incidence of acute AMR, this percent is 1-6% in patients with undetected DSA.
Weak pretransplant DSA will be associated with graft injury but subclinical and this will lead chronic graft damage and exposure of endothelium, which leads to De novo DSA formation, and there is decrease in immunosuppression doses in the late period after transplantation and this will be added factor to induction of chronic AMR.
DSA can be detected with high sensitive luminex –SAB which detects low level of DSA .
There are multiple risk factors for de novo DSA formation as previous transplant, blood transfusion, pregnancy, previous infection, previous attacks of rejection, surgery, HLA mismatch, under immunosuppression by either dose reduction protocol or non-adherence (non-compliance) to immunosuppressive medications, in addition to young age, or deceased donor transplantation.
De novo DSA formation is associated with 10 fold increase in graft loss and 40% decrease in graft survival at 10 years than the patients have no de novo DSA.
Monitoring of DSA after transplant is very important especially in the early period, and after that depending on risk factors pretransplant like sensitized or not, 1st or 2nd graft, immunosuppression protocol changed or reduced, suspected noncompliance to medications, and if DSA is detected, biopsy should be done to confirm chronic AMR.
All patients should be submitted for DSA detection once yearly.
What do you mean by (Weak Pretransplant DSA)?
not high level, or not inducing evident clinical symptoms
T cell expresses class I HLA, and B cell expresses both class I & class II HLA. Weak pre transplant DSA means positive T cell cross match and and Negative B cell crossmatch(class I = low titre, and class II Ab = is negative )