Nope. Risk of immunological reaction still possible.
AMAL Anan
2 years ago
A2 is antigenic but with low level so can’t consider as a universal donor as O group
Assafi Mohammed
2 years ago
Although blood group A2 are less immunogenic because of low expression of ABO antigen on the surface of erythrocyte, but still may induce immunogenic reaction. That’s why we can’t deal with A2 as blood group O.
amiri elaf
2 years ago
* Can we treat blood group A2 as group O, i.e., a universal donor?
A2 is less antigenic when compared to A1, but still antigenic, so we can not consider it a universal donor like blood group O, and it need level monitoring before transplantationtrans.
Mahmoud Hamada
2 years ago
IMHO, No.
blood group O persons express no antigens , while blood group A2, although less immunogenic , they express A2 antigen which still may induce immunogenic reaction.
Hamdy Hegazy
2 years ago
Can we treat blood group A2 as group O, i.e., a universal donor? No. We can’t treat blood group A2 as a universal donor as group O.
Blood group A2 is less immunogenic than group A1, but it is still immunogenic not like blood group which is not immunogenic. We need to check the level of anti A2 antibody IgG & IgM titer before transplantation, if it is less than 1:16 it is usually associated with good short-term graft outcomes, high anti-A2 IgG antibody titers are associated with ABMR and poor graft survival
Fatima AlTaher
2 years ago
In ABO, The order of immunogenicity A1 >B >A2
A2 is less immunogenic than other groups. OPTN in 2014 permitted transplanting A2 and A2B kidneys to blood group B recipient. So A2 is less antigenic than others but more than o group.
Tahani Ashmaig
2 years ago
▪︎No, although The ABO blood subgroup A2 expresses lower levels of A antigen on the cell surface and is less immunogenic toward anti-A immunoglobulin present in blood type O or B recipients, attention should be paid to IgM titers in establishing individual center selection criteria for A2 to B kidney transplants.
▪︎Study showed a high incidence of early acute rejection and thrombotic microangiopathy in A2 to O kidney transplants with high recipient anti-A IgM titers despite low IgG titers [1] . ___________________
Ref:
[1] Joshua Tierney et al. Transplantation of ABO A2 kidneys into O recipients: do IgM anti-A1 titers matter?. Clin Transplant. 2015 Apr.
MICHAEL Farag
3 years ago
Blood group A consists of two subtypes, A1 and A2, or more appropriately “non-A1.” Approximately 80 percent of individuals in the United States with blood group A express A1 The antigenic expression of A2 is quantitatively and qualitatively less than that of A1, and the overall immunogenic risk based on antigen expression alone is A1 >B >A2 . Given the lower immunogenic risk of the A2 antigen, donor A2 kidneys can generally be successfully transplanted into recipients with low pretransplant anti-A titers without the use of desensitization
Balaji Kirushnan
3 years ago
There have been speculations of Blood group A2 being used as universal donor in place of O blood group. This is due to Blood group A2 being less immunogenic and is less expressed on the endothelium.
Blood group A are divided into A1 and A2. A1 accounts for 80% of the variety. A2 accounts for 20% of the remaining groups. In many laboratories A1 and A2 subtyping are not done unless requested.
In 2002, Deceased donor renal transplant by the OPTN, allowed transplant of A2 or A2B kidneys from deceased donors to patients with B blood group recipients. They should have Anti A titres repeated at 3 monthly intervals months and should be less than 1:8 for 2 consecutive samples. In this way blood group B recipients moved faster in the deceased donor program by enhancing the organ source donor pool. Atleast half of B group recipients benefitted in this approach and the overall patient and graft survival was comparable. It could benefit O group recipents also. The Ethical question of whether it is fair to all other blood group remains a matter of debate.
No, i will not consider A2 group as universal donor. I would still do Anti A titre in the recipient and check for raising titre within 2 weeks of transplant.
Mohamed Essmat
3 years ago
No, we can’t , anti-A antibody titre should be done before transplantation to determine the need for antibody removal and the risk of antibody mediated rejection.
Mohamed Ghanem
3 years ago
No
however, blood group A2 used for donation to both groups B and O is useful in ABOi-KT (less antigenic and expands the donor pool)
still, the need for assessment of Anti-A2 antibodies before KT with the same precautions is mandatory
if high titer we will need desensitization
and follow of Anti-A2 titer 2 weeks after transplantation
No, A2 donors are still ABOi-TX. Although they are less antigenic but express A2 Ags. But O blood group has no antigens. So antibody titer against A2 Ag should be measured and kept in a low titer before TX.
mohamed hefzy
3 years ago
Can we treat blood group A2 as group O, i.e., a universal donor?
No.
We cannot treat blood group A2 as a universal donor.
Although A2 is less immunogenic than A1, still the level of anti-A2 antibody titres is important in deciding the acceptance of the A2 donor for an ABO incompatible recipient
No , in spite A2 is considered low antigenic , we still need to measure antibodies titer before and few weeks after renal transplant and high titer carry high risk for ABMR , also high titer will need desensitization protocols
Last edited 3 years ago by Abdelsayed Wasef
Mahmud Islam
3 years ago
Although some centres transplanted A2 donors with standard immunosuppression, we can not consider blood group A2 universal donors. notably, the frequency differs from nation to nation. Transplantation even in compatible ABO needs monitoring
CARLOS TADEU LEONIDIO
3 years ago
No, ins´t necessary. Its because organs from group A2 donors have lower immunogenicity of organs.
REFERENCE:
Morath C, Zeier M, Döhler B, Opelz G and Süsal C (2017) ABO-Incompatible Kidney Transplantation. Front. Immunol. 8:234. doi: 10.3389/fimmu.2017.00234
No,
Although blood group A2 is considered less immunogenic as it displays less A antigen, anti-A antibody titer should be done before transplantation to determine the need for antibody removal and the risk of antibody mediated rejection.
Patients with low anti-A antibody titer can proceed to transplantation using conventional immunosuppression without desensitization which decrease the cost and increase access to living donor ABO incompatible transplant with decreased morbidity.
Masterson R, Hughes P, Walker RG, Hogan C, Haeusler M, Robertson AR, Millar R, Suh N, Cohney SJ. ABO incompatible renal transplantation without antibody removal using conventional immunosuppression alone. American journal of transplantation. 2014 Dec;14(12):2807-13.
No . Although blood group A2 antigens have low immunologinicity , it still mandatory to measure anti -A2 antibodies titter in the recipients before deciding to do transplantation or not , so we can not regard it as blood group O.
Blood group A2 cannot be regarded as a universal donor.A2 is less immunogenic than A1, but level of anti-A2 antibody titers remains important in deciding transplantation
Anti A2 antibody tires ≤1:16 is associated with good results regarding graft outcome
High anti A1 IgG antibody titers can result in AMR with poor graft outcome.
No, still we can’t use blood group A2 as a universal donor because we still need to measure anti A2 titer in recipient blood before transplantation
if 2 readings of antibody titer below 1/8 you can use this potential donor for this potential recipient.
References:
Neetika Garg,Leza Warnke,Robert R. Redfield.Discrepant subtyping of blood type A2 living kidney donors
A. A. R. Tobian, R. S. Shirey, R. A. Montgomery, W. Cai, M. Haas, P. M. Ness, K. E. King. ABO Antibody Titer and Risk of Antibody-Mediated Rejection in ABO-Incompatible Renal Transplantation
American Journal of TransplantationVolume 10, Issue 5 p. 1247-1253
First published: 20 April 2010 https://doi.org/10.1111/j.1600-6143.2010.03103.x
Citations: 82
Though A2 is less immunogenic than A1 and other blood groups..We must see what is antibody titre present in receipient against Donor A2 .If titre is high ,we need to do same desentization protocol as we are using with other ABOi transplant.So we cant treat A2 blood group as universal donor.
The ABO blood group antigens are potent transplantation antigens, so transplantation across ABO barriers usually leads to irreversible hyper-acute rejection. The criteria that determine kidney distribution according to ABO group is the same as for blood transfusions. Group O represent universal donor, and group AB represents universal recipient.
Blood group A2 represents about 20% of group A individuals. these individuals have reduced levels of A antigen on graft endothelium. They allow an exception to the ABOincompatibility barrier because A2 kidneys can be safely transplanted into O or B recipients with low preoperative titers of isoagglutinin. Transplantation of A2 kidneys into B or AB recipients is routine in some centres and is being encouraged under the new KAS. Because patients with blood group O or B wait longer for a blood group–identical donor.
reference:
Handbook of kidney transplantation, Gabriel M. Danovitch 6th edition
Blood group type A carries A1 or A2. The expression of A2 antigen is weaker than that of A1 antigen . A2 kidney may be less likely to suffer antibody rejection in the presence of anti-A antibody.Between 14 and 20% of A donors would be expected to be A2. However the consideration of donors with A2 subgroup as a universal donor is not safe . The eligibility for donation depend on the anti-A titre .Assuming a cut-off of anti-A titres of 1 in 16, 3% of Group O but 68% of Group B waiting list recipients would be eligible for a deceased donor A2 transplant .The dangerous of these minor incompatibilities can be avoided by desensitization .
No, because Blood group O has no antigens unlike Blood group A2 has A2 antigen and the recipient antibody titer against A2 antigen should be measured and followed
Ahmed Abd El Razek
3 years ago
blood group A2 despite being less antigenic ad of less incidence of AMR, yet they still express A2 antigens, unlike blood group O which have no antigens at all being more safe to be considered as a universal donor while blood group A2 is not.
Sahar elkharraz
3 years ago
No, blood group A2 is not universal donor
Despite blood group A2 is less antigenic and low immunological risk but still there is risk of AMR.
it’s still need desensitisation protocol and monitoring to anti A2 antibodies in blood but less aggressive monitoring.
it’s need low desensitisation dose to avoid graft loss
Ben Lomatayo
3 years ago
Results of ABOi-transplant are better when when transplanting kidneys from A2 donors to O recipients.
The A2 sub-type does not have circulating antigens linked von Willebrand factors.
A2 subtype is less immuno-genic compared to A1
So, A2 to O can proceed safely provided that the recipient had low levels of anti-A antibodies.
Ibrahim Omar
3 years ago
A2 is a subtype of blood group A. it is present in about 20 % of people with blood group A. A1 is present in the remaining 80 % of those people.
A2 is less antigenic and so less immunogenic. it can induce a mild form of antibody mediated rejection.
it is not considered as blood group 0 and can’t be considered as universal donor.
in potential kideny recipients, the anti- A2 titre should be checked as pre-procedure ;
1- if the titre is low, transplantation can be proceeded with regular follow up of the titre post-transplantation.
2- if the titre is high, desesnsitization protocols can be applied before transplantation.
. Can we treat blood group A2 as group O, i.e., a universal donor?
No,because blood group O does not have any antigen while blood group type A2 has antigen so there is the risk of sensitization and AMR and we need to measure IgG and IgM titer before proceeding to transplantation.
-The expression of the A2 antigen is weaker than that of the A1 antigen.
– The A2 subtype constitutes approximately 20% of blood type A in white races, while it is only 0.15% in the Japanese population.
-A2 kidney may be less likely to suffer antibody rejection in the presence of anti-A antibodies.
Reference:
Masaki Muramatsu, Hector Daniel Gonzalez et al. ABO incompatible renal transplants: Good or bad?. World J Transplant 2014 March 24; 4(1): 18-29
ISSN 2220-3230 (online)
Blood group antigens have variable immunogenic potential. Blood group A is divided into A1(80%) and A2 -20%. Blood group A1 and B are considered as major and A2 as minor challenge to kidney transplantation . A1 is more immunogenic than B whilst A2 is least immunogenic. As blood group A2 is still immunogenic so antibody titres are expected and should be taken into consideration when planning transplant. Higher anti A2 titres can lead to AMR and poor outcome. A2 incompatible transplantation is safe in if Anti A2 titres are <16. Hence it cannot be a universal donor like blood group O. Reference Christian Morath et al, ABO-Incompatible Kidney Transplantation. Front Immunol. 06 March 2017
Hemant Sharma
Admin
3 years ago
Please see the following Kidney Advisory group document that resonances with responses.
No, We should not regard blood group A2 as a universal donor.
It is known that A2 is less immunogenic than A1, but still the level of anti-A2 antibody titers important in determining the transplantation
The level of ABO antibody titers still important determinant in ABO incompatible transplants.
Anti A2 antibody tires ≤1:16 have good results in graft outcome
High anti A1 IgG antibody titers can lead to AMR and poor graft outcomes.
So, it still need more evidences or study to look at the compatibility to regard as universal donor.
References:
Neetika Garg,Leza Warnke,Robert R. Redfield.Discrepant subtyping of blood type A2 living kidney donors
A. A. R. Tobian, R. S. Shirey, R. A. Montgomery, W. Cai, M. Haas, P. M. Ness, K. E. King. ABO Antibody Titer and Risk of Antibody-Mediated Rejection in ABO-Incompatible Renal Transplantation
American Journal of TransplantationVolume 10, Issue 5 p. 1247-1253
First published: 20 April 2010 https://doi.org/10.1111/j.1600-6143.2010.03103.x
Citations: 82
Can we treat blood group A2 as group O, i.e., a universal donor?The tissue of the A2 subgroup expressed reduced amount of antigen
compared of Antigen subgroup less reacting with the anti-A1 antibody ,naturally in the serum group O and B recipient.
clinical trials started kidney of A2 subgroup into group O and B recipient with no special pre treatment and standard immunosuoression therapy ,number of graft loss expressed but several long time survival graft .
a few centers have adapted the concepts of A2 to non kidney transplant with successful result when the recipient anti A titre are lower or reduced prior to transplant .
need more trials and studies to know more about the out come of this transplantation and graft survival to reply this question .
references
1-Starzl TE,MarchioroTL,holmeJH,et al.Renalhomo graft in patients with major donor-recipient blood group incompatibilities. surgery 1964,55.195.
Thank you, Dr Manal, agree provided the titre is acceptable, but we can not consider it a universal donor without checking the titre (to me would not be considered a universal donor if I need ti check the titre)
Weam Elnazer
3 years ago
The immunogenic risk determined only by Ag expression is A1>B>A2.
It is possible that A2 will be approved in ABOi because of the minimal immunogenic risk and in order to extend the donor pool, which would lower the time spent on dialysis.
In general, donor A2 kidneys can be safely transplanted into recipients with blood groups B or O if the donor’s anti-A titers are low prior to the transplant but still the risk of AMR is still present.
As a result, blood type A2 cannot be considered a universal donor like blood group O.
– Neetika Garg,Leza Warnke,Robert R. Redfield.Discrepant subtyping of blood type A2 living kidney donors
Answer: No
The A2 blood group is expressed at lower levels than A1 and appears to pose a lower barrier to transplantation compared with blood group A1.
A2 kidneys transplanted into O or B recipients may need less pretransplant PEX or IA
However, some studies have suggested that kidneys from A2/A2B donors transplanted into blood group B or O patients who have high titers of A isoagglutinins (anti-A immunoglobulin [Ig]G) can develop rejection and graft loss
A2 donors may be preferable for O or B recipients, they should never the less be treated as fully ABOi transplants
Antibody titers were determined before and after each posttransplant TPE treatment, 72 h after the last planned treatment, at weekly intervals for the first month and at 2, 3, 6 and 12 months.
Reference
1- Bryan, Christopher F.1,8; Winklhofer, Franz T.2; Murillo, Daniel3; Ross, Gilbert4; Nelson, Paul W.5; Shield, Charles F. III6; Warady, Bradley A.7. Improving Access to Kidney Transplantation without Decreasing Graft Survival: Long-Term Outcomes of Blood Group A2/A2B Deceased Donor Kidneys in B Recipients. Transplantation: July 15, 2005 – Volume 80 – Issue 1 – p 75-80
doi: 10.1097/01.TP.0000164288.82238.52.
2-A. A. R. Tobian, R. S. Shirey, R. A. Montgomery, W. Cai, M. Haas, P. M. Ness, K. E. King. ABO Antibody Titer and Risk of Antibody-Mediated Rejection in ABO-Incompatible Renal Transplantation
American Journal of TransplantationVolume 10, Issue 5 p. 1247-1253
First published: 20 April 2010 https://doi.org/10.1111/j.1600-6143.2010.03103.x
Citations: 82
3- Nicholas Torpey, Nadeem E Moghal, Evelyn Watson, and David Talbot. OSH Renal Transplantation. Published online: Oct 2011.
According to understanding to the question
yes i can consider the blood group A2 as universal donor such as the blood group o
The ABO subgroup A2 has been reported to be less reactive with the anti-A1 antibody naturally occurring in the serum of group O and B recipients and to occur in approximately 20% of group A individuals We recommend the screening of A donors for the A2 subgroup in both the cadaver-donor and living-related groups, and suggest that the utilization of A2 donors in non-A patients may contribute to the transplantation of group O and highly sensitized patients–and, in some cases, improve the degree of HLA matching
REF: Successful transplantation of blood group A2 kidneys into non-A recipient
Thank you, Dr Manal, agree provided the titre is acceptable, but we can not consider it a universal donor without checking the titre (to me would not be considered a universal donor if I need ti check the titre)
Zahid Nabi
3 years ago
The ABO blood group consists of four common categories (A, B, AB, and O), with types A and O most frequently found in the United States population. Antigen is expressed on red blood cells, lymphocytes, and platelets, as well as epithelial and endothelial cells. Formation of blood group antibodies occurs against those antigens not native to the host. Thus, antibodies to both A and B are found in an individual with blood type O, while an individual with blood type AB has no antibodies to A or B antigens. Given the distribution of blood group antigens in the United States, the waiting time on the deceased-donor allograft (DDA) list is markedly prolonged for patients with blood group B or O.
Blood group A consists of two subtypes, A1 and A2, or more appropriately “non-A1.” Approximately 80 percent of individuals in the United States with blood group A express A1 The antigenic expression of A2 is quantitatively and qualitatively less than that of A1, and the overall immunogenic risk based on antigen expression alone is A1 >B >A2 . Given the lower immunogenic risk of the A2 antigen, donor A2 kidneys can generally be successfully transplanted into recipients with low pretransplant anti-A titers without the use of desensitization .
Inspite if all this we cannot consider A2 as universal donor however using such donor efficiently can reduce waiting time for many patients
The basic structure of ABO system is frucosyl galactase H-Ag of O-type blood which present on RBC surface & other tissues. other blood group Ags differ from H-Ag by presence of additional sugar moiety. So blood group can be a universal donor you blood group A2 can’t be universal donor due to presence of these Ags that can lead to immune response activation.
References:
Rahfeld P and Withers S. Toward universal donor blood: Enzymatic conversion of A and B to O type. J.Biol.Chem, 2020; 295(2):325-334.
The writing style and grammar need to be improved, Dr. Ban to deliver the best response.
Doaa Elwasly
3 years ago
For the A-blood group specifically there are two phenotypes with different immunogenicity. The A1 phenotype expresses more A epitopes than A2 as the A2 epitope can only be expressed on two of four possible core saccharide chains of the ABO antigen, whereas A1 epitopes can be expressed on all four rendering A2 antigen less immunogenic .Multiple studies concluded that A2 grafts can be safely transplanted into blood group O recipients when ABO-matched grafts are not available indicating that transplantation of A2 kidney or liver grafts was not stopped by high anti-A titers ,also transplanting of A2B-liver grafts to blood group B recipients could have same outcomes of A2-to-O transplantation without the need for induction therapy or maintenance agents. Theoretically, A2-to-B liver transplantation should also be safe.But no enough data was available to confirm those possibilities. (1)
Forbes RC et al concluded that A2i kidney transplantation didnot adversely affect graft or patient survival and it was has been included in the new Kidney AllocationSystem and is considered a favorable option for transplant centers to increase transplant volume and reduce wait times for disadvantaged B waitlist recipients.(2)
Martins PN etal noticed an increase in A2i Deceased Donor Kidney Transplanation among blood group B recipients, in fact the improvement in access for those minorities need to be implicated through the A2/A2B→B component of the new allocation system. In order for A2 incompatible transplantation to be performed and in efforts to increase blood group B access to transplantation among minorities, a protocol for A2 incompatible transplantation need to be done , with standardized assessment of isoagglutinin titers and putting cut points for anti-A titer levels before transplantation.(3)
Meanwhile till now blood group O is the only blood group to be considered as a universal donor
Reference
1-Kluger, Michael D., Guarrera, James V. ,Olsen, Sonja K. , Brown, Robert S. Jr; Emond, Jean C., , Cherqui, Daniel. .Safety of Blood Group A2-to-O Liver Transplantation, Transplantation Journal, 2012 – 94 (5): 526-531
2-Forbes RC, Feurer ID, Shaffer D. A2 incompatible kidney transplantation does not adversely affect graft or patient survival. Clin Transplant. 2016 May;30(5):589-97.
3-Martins PN, Mustian MN, MacLennan PA, Ortiz JA, Akoad M, Caicedo JC, Echeverri GJ, Gray SH, Lopez-Soler RI, Gunasekaran G, Kelly B, Mobley CM, Black SM, Esquivel C, Locke JE. Impact of the new kidney allocation system A2/A2B → B policy on access to transplantation among minority candidates. Am J Transplant. 2
You need to answer the question first.
The immunology concept with liver transplantation is a bit different.
Be specific to the point on future responses.
Filipe prohaska Batista
3 years ago
Despite being less immunogenic than A1 carriers, individuals who have A2 antigens can trigger an immunogenic response and, therefore, could not be universal donors. The only blood group that lacks antigens is group O.
However, with appropriate therapies to minimize the antibodies produced by this antigen, desensitization in this profile should be considered to make it a potential donor.
Mohamed Mohamed
3 years ago
2. Can we treat blood group A2 as group O, i.e., a universal donor?
Of the 4 main blood types, A, B, AB, & O, only O can be given to any patient (universal donor). A & B blood differ from the O type in the presence of an additional sugar antigen (GalNAc & Gal, respectively) on the core H-antigen found on O-type RBCs. So conversion of A, B, & AB RBCs to O-type RBCs could be done by removal of that sugar with an appropriate glycosidase. New α-galactosidases & α-N-acetylgalactosaminidases were identified in 2007, allowing improved conversion of B & the 1st useful conversions of A-type RBCs. In 2019, 2 more efficient enzymatic systems, involving a GalNAc deacetylase & a galactosaminidase, for A conversion were discovered. Removal of the A/B antigens from the donor organ prior to transplant would greatly reduce the need for IS & possibly PP. Studies have not progressed beyond the use of glycosidases to remove tissue surface antigens from whole organs during perfusion. However the appearance of improved enzymes and improved perfusion procedures is expected to lead a new hope in this regard. A2, compared to A1 is less expressed & less immunogenic. A2 donors have been successfully transplanted into B & A2B recipient. But this cannot be literally considered as a universal donor because there is still the need for IS & PP in this setting. Reference J Biol Chem. 2020 Jan 10; 295(2): 325–334. Published online 2019 Dec 2. doi: 10.1074/jbc.REV119.008164
For the timebeing A2 or any other blood group can not be treated as a universal donor; A2 is less expressed and less immunogenic but still would not be considered as universal donor. But enzymatic manipulation can make such changes in the future.
saja Mohammed
3 years ago
Can we treat blood group A2 as group O, i.e., a universal donor?
The ABO group consists of four subtypes (A, B, AB, O)
A and O blood groups are the most frequent subtypes in US population, both A and B abs found on blood group O,
Both blood group B and O have prolong waiting list for DDA
A2 phenotype around 10% of US and 8% in black race, 0% in Asia.
The answer is no we cannot consider A2 group as a universal donor like group O, but can be limited for minor ethnic background (African American black with blood group B
A2 incompatible transplantation consider minor donor group with less immunogenicity compared to A1. Minor ABO incompatibility’ from blood group A2 donors into blood group B recipients. This significantly increased the number of such transplants done without desensitization ,also less cost and allow to reduce waiting list without compromise the graft survival (2) should be limited to those with low anti-IgG titer < 1:8 as there is still a risk of post-transplant rebound of anti – IgG antibodies with increased risk of AMR (3).
References:
1-Bryan CF, Winklhofer FT, Murillo D, et al. Improving access to kidney transplantation without decreasing graft survival: long-term outcomes of blood group A2/A2B deceased donor kidneys in B recipients. Transplantation. 2005; 80:75–80
2- Gilbert AJ. Kidney transplantation across minor ABO incompatibility: the use of A2 to B transplants. Curr Opin Organ Transplant. 2019 Aug;24(4):365-369.
3- Williams WW, Cherikh WS, Young CJ, Fan PY, Cheng Y, Distant DA, Bryan CF. First Report on the OPTN National Variance: Allocation of A2 /A2 B Deceased Donor Kidneys to Blood Group B Increases Minority Transplantation. Am J Transplant. 2015 Dec;15(12):3134-42. doi: 10.1111/ajt.13409. Epub 2015 Aug 4. PMID: 26372745.
Excellent response and great insight on how this may increase access to transplantation. Thank you, Dr. Saja
kumar avijeet
3 years ago
1.Blood group A2 can’t be treated as universal donor,as it has an antigen not like group o,though less immunogenic than other group like A1>B>A2 but still not zero.
Hence A2 titre less than 1/16 is advisable.
Mohamed Saad
3 years ago
Blood group A consists of two subtypes, A1 and A2. Approximately 80 % of individuals in North America with blood group A express A1. Antigenic expression of A2 is quantitatively and qualitatively less than that of A1. Immunogenic risk based on antigen expression alone is A1>B>A2 (1). We can considered it safe but not as universal donor and it dependent on anti-A2 titers which better to be ≤16. A2-incompatible transplantation is safe in patients with anti-A2 titers ≤16 with excellent short-term kidney allograft outcomes (2). A2i kidney transplantation does not adversely affect graft or patient survival (3). Or can be called semi-compatible. References: 1-ABO Incompatible Kidney Transplantation (Part 1) lecture,Abu baker Hassan Associate Professor (ASNRT). 2-Azzi Y, Nair G, Loarte-Campos P, et al . A Safe Anti-A2 Titer for a Successful A2 Incompatible Kidney Transplantation: A Single-center Experience and Review of the Literature. Transplant Direct. 2021 Jan 26;7(2):e662. doi: 10.1097/TXD.0000000000001099. PMID: 33521251; PMCID: PMC7837880. 3-Forbes RC, Feurer ID, Shaffer D. A2 incompatible kidney transplantation does not adversely affect graft or patient survival. Clin Transplant 2016; 30:589.
Huda Al-Taee
3 years ago
No, we cannot. Although the A2 blood group is less immunogenic, the level of anti A antibody ( IgG ) is important for ABOi transplantation.
Reference:
Tobian AA, Shirey RS, Montgomery RA, Cai W, Haas M, Ness PM, King KE. ABO antibody titer and risk of antibody-mediated rejection in ABO-incompatible renal transplantation. Am J Transplant. 2010 May;10(5):1247-53.
It has been widely reported that ABO blood subgroup A2 kidneys have reduced expression of antigen on endothelial surfaces.
A2 kidneys are biologically similar to O kidneys, which means they are more universally accepted by recipients of all blood types, including blood type B.
Many centers have reported their successful experiences with A2 incompatible kidney transplants, most are for blood group B recipients.
Similar success rates for living A2 incompatible transplants to B and O recipients have also been reported.
Patients with blood groups B & O have to wait for a long time to find a blood group compatible donor, so using donors with blood group A2 will shorten their waiting time and expand the donor pool.
However, previous single-centre studies have shown acceptable outcomes for A2 incompatible kidney transplants when the recipient’s pre-transplant anti-A IgG titer is less than or equal to 1:8, so there is a role for Anti-A IgG titer for successful transplantation.
Reference:
Forbes RC, Feurer ID, Shaffer D. A2 incompatible kidney transplantation does not adversely affect graft or patient survival. Clin Transplant 2016: 30: 589–597.
Shereen Yousef
3 years ago
Blood type B and O kidney transplant candidates have the longest wait-times on dialysis.
Subtyping of A and AB donors is important in kidney transplantation because among non-A1 individuals, the A antigenic expression is both quantitatively and qualitatively lower. As a result, kidneys from non-A1 (or non-A1B) donors can be successfully transplanted into blood type B or O recipients (or B) using the same immunosuppression protocols as ABO-compatible transplantation, without desensitization, as long as anti-A titers are low in the recipient at the time of transplantation.
Inaccurate A2 subtyping represents a significant lost opportunity in transplantation, especially in KPD where A2 donors can not only facilitate living donor transplantation for O and highly sensitized candidates, but can also facilitate additional living donor transplants.
Neetika Garg,Leza Warnke,Robert R. Redfield.Discrepant subtyping of blood type A2 living kidney donors: Missed opportunities in kidney transplantation.Clinical TransplantationVolume 35.2021
As A2 is weakly antigenic compared to A1
The incidence of A2 to A1 is 20% in white race
Yet it is 0.15% in Japanese!
This makes titre monitoring mandatory as a decision is taken to go with the Tx.
You are right work up is needed thoroughly so as not to decline potentially good cases.
Alaa eddin salamah
3 years ago
Case Scenario II Can we treat blood group A2 as group O, i.e., a universal donor?
Blood group A constitutes 45% of all ABO system, 9% is A2.
Immunogenic risk based on Ag expression alone is A1>B>A2.
A2 may be accepted in ABOi due to low immunogenic risk, but it is not equal to zero.
Nope. Risk of immunological reaction still possible.
A2 is antigenic but with low level so can’t consider as a universal donor as O group
Although blood group A2 are less immunogenic because of low expression of ABO antigen on the surface of erythrocyte, but still may induce immunogenic reaction. That’s why we can’t deal with A2 as blood group O.
* Can we treat blood group A2 as group O, i.e., a universal donor?
A2 is less antigenic when compared to A1, but still antigenic, so we can not consider it a universal donor like blood group O, and it need level monitoring before transplantationtrans.
IMHO, No.
blood group O persons express no antigens , while blood group A2, although less immunogenic , they express A2 antigen which still may induce immunogenic reaction.
Can we treat blood group A2 as group O, i.e., a universal donor?
No. We can’t treat blood group A2 as a universal donor as group O.
Blood group A2 is less immunogenic than group A1, but it is still immunogenic not like blood group which is not immunogenic.
We need to check the level of anti A2 antibody IgG & IgM titer before transplantation, if it is less than 1:16 it is usually associated with good short-term graft outcomes, high anti-A2 IgG antibody titers are associated with ABMR and poor graft survival
In ABO, The order of immunogenicity A1 >B >A2
A2 is less immunogenic than other groups. OPTN in 2014 permitted transplanting A2 and A2B kidneys to blood group B recipient. So A2 is less antigenic than others but more than o group.
▪︎No, although The ABO blood subgroup A2 expresses lower levels of A antigen on the cell surface and is less immunogenic toward anti-A immunoglobulin present in blood type O or B recipients, attention should be paid to IgM titers in establishing individual center selection criteria for A2 to B kidney transplants.
▪︎Study showed a high incidence of early acute rejection and thrombotic microangiopathy in A2 to O kidney transplants with high recipient anti-A IgM titers despite low IgG titers [1] . ___________________
Ref:
[1] Joshua Tierney et al. Transplantation of ABO A2 kidneys into O recipients: do IgM anti-A1 titers matter?. Clin Transplant. 2015 Apr.
Blood group A consists of two subtypes, A1 and A2, or more appropriately “non-A1.” Approximately 80 percent of individuals in the United States with blood group A express A1 The antigenic expression of A2 is quantitatively and qualitatively less than that of A1, and the overall immunogenic risk based on antigen expression alone is A1 >B >A2 . Given the lower immunogenic risk of the A2 antigen, donor A2 kidneys can generally be successfully transplanted into recipients with low pretransplant anti-A titers without the use of desensitization
There have been speculations of Blood group A2 being used as universal donor in place of O blood group. This is due to Blood group A2 being less immunogenic and is less expressed on the endothelium.
Blood group A are divided into A1 and A2. A1 accounts for 80% of the variety. A2 accounts for 20% of the remaining groups. In many laboratories A1 and A2 subtyping are not done unless requested.
In 2002, Deceased donor renal transplant by the OPTN, allowed transplant of A2 or A2B kidneys from deceased donors to patients with B blood group recipients. They should have Anti A titres repeated at 3 monthly intervals months and should be less than 1:8 for 2 consecutive samples. In this way blood group B recipients moved faster in the deceased donor program by enhancing the organ source donor pool. Atleast half of B group recipients benefitted in this approach and the overall patient and graft survival was comparable. It could benefit O group recipents also. The Ethical question of whether it is fair to all other blood group remains a matter of debate.
No, i will not consider A2 group as universal donor. I would still do Anti A titre in the recipient and check for raising titre within 2 weeks of transplant.
No, we can’t , anti-A antibody titre should be done before transplantation to determine the need for antibody removal and the risk of antibody mediated rejection.
No
however, blood group A2 used for donation to both groups B and O is useful in ABOi-KT (less antigenic and expands the donor pool)
still, the need for assessment of Anti-A2 antibodies before KT with the same precautions is mandatory
if high titer we will need desensitization
and follow of Anti-A2 titer 2 weeks after transplantation
Renal transplantation across the ABO barrier using A2 kidneysA M Alkhunaizi 1, A M de Mattos, J M Barry, W M Bennett, D J Norman
No, A2 donors are still ABOi-TX. Although they are less antigenic but express A2 Ags. But O blood group has no antigens. So antibody titer against A2 Ag should be measured and kept in a low titer before TX.
Can we treat blood group A2 as group O, i.e., a universal donor?
No.
We cannot treat blood group A2 as a universal donor.
Although A2 is less immunogenic than A1, still the level of anti-A2 antibody titres is important in deciding the acceptance of the A2 donor for an ABO incompatible recipient
No , in spite A2 is considered low antigenic , we still need to measure antibodies titer before and few weeks after renal transplant and high titer carry high risk for ABMR , also high titer will need desensitization protocols
Although some centres transplanted A2 donors with standard immunosuppression, we can not consider blood group A2 universal donors. notably, the frequency differs from nation to nation. Transplantation even in compatible ABO needs monitoring
No, ins´t necessary. Its because organs from group A2 donors have lower immunogenicity of organs.
REFERENCE:
Morath C, Zeier M, Döhler B, Opelz G and Süsal C (2017) ABO-Incompatible Kidney Transplantation. Front. Immunol. 8:234. doi: 10.3389/fimmu.2017.00234
Well done.
No,
Although blood group A2 is considered less immunogenic as it displays less A antigen, anti-A antibody titer should be done before transplantation to determine the need for antibody removal and the risk of antibody mediated rejection.
Patients with low anti-A antibody titer can proceed to transplantation using conventional immunosuppression without desensitization which decrease the cost and increase access to living donor ABO incompatible transplant with decreased morbidity.
Masterson R, Hughes P, Walker RG, Hogan C, Haeusler M, Robertson AR, Millar R, Suh N, Cohney SJ. ABO incompatible renal transplantation without antibody removal using conventional immunosuppression alone. American journal of transplantation. 2014 Dec;14(12):2807-13.
Well done.
No . Although blood group A2 antigens have low immunologinicity , it still mandatory to measure anti -A2 antibodies titter in the recipients before deciding to do transplantation or not , so we can not regard it as blood group O.
Well done.
Although it had less immunogenicity but still antibodies can be formed to word it ,so we couldn’t accepted as universal donor like o blood group
Well done. Nice to read your reply
Blood group A2 cannot be regarded as a universal donor.A2 is less immunogenic than A1, but level of anti-A2 antibody titers remains important in deciding transplantation
Anti A2 antibody tires ≤1:16 is associated with good results regarding graft outcome
High anti A1 IgG antibody titers can result in AMR with poor graft outcome.
Well done. Nice to read your reply
No, still we can’t use blood group A2 as a universal donor because we still need to measure anti A2 titer in recipient blood before transplantation
if 2 readings of antibody titer below 1/8 you can use this potential donor for this potential recipient.
References:
Neetika Garg,Leza Warnke,Robert R. Redfield.Discrepant subtyping of blood type A2 living kidney donors
A. A. R. Tobian, R. S. Shirey, R. A. Montgomery, W. Cai, M. Haas, P. M. Ness, K. E. King. ABO Antibody Titer and Risk of Antibody-Mediated Rejection in ABO-Incompatible Renal Transplantation
American Journal of TransplantationVolume 10, Issue 5 p. 1247-1253
First published: 20 April 2010
https://doi.org/10.1111/j.1600-6143.2010.03103.x
Citations: 82
Well done. Nice to read your reply
No , although A2 Ag is less immunogenic than A1 , it is still incompatible to those with blood group B & AB ( as having Anti A Ab in their sera ) .
Well done. Nice to read your reply
Though A2 is less immunogenic than A1 and other blood groups..We must see what is antibody titre present in receipient against Donor A2 .If titre is high ,we need to do same desentization protocol as we are using with other ABOi transplant.So we cant treat A2 blood group as universal donor.
Well done. Thank you
No, we can not, although; it is less immunologic.
The ABO blood group antigens are potent transplantation antigens, so transplantation across ABO barriers usually leads to irreversible hyper-acute rejection. The criteria that determine kidney distribution according to ABO group is the same as for blood transfusions. Group O represent universal donor, and group AB represents universal recipient.
Blood group A2 represents about 20% of group A individuals. these individuals have reduced levels of A antigen on graft endothelium. They allow an exception to the ABOincompatibility barrier because A2 kidneys can be safely transplanted into O or B recipients with low preoperative titers of isoagglutinin. Transplantation of A2 kidneys into B or AB recipients is routine in some centres and is being encouraged under the new KAS. Because patients with blood group O or B wait longer for a blood group–identical donor.
reference:
Handbook of kidney transplantation, Gabriel M. Danovitch 6th edition
Well done. Thank you
Blood group type A carries A1 or A2. The expression of A2 antigen is weaker than that of A1 antigen . A2 kidney may be less likely to suffer antibody rejection in the presence of anti-A antibody.Between 14 and 20% of A donors would be expected to be A2. However the consideration of donors with A2 subgroup as a universal donor is not safe . The eligibility for donation depend on the anti-A titre .Assuming a cut-off of anti-A titres of 1 in 16, 3% of Group O but 68% of Group B waiting list recipients would be eligible for a deceased donor A2 transplant .The dangerous of these minor incompatibilities can be avoided by desensitization .
Reference ;
https://nhsbtdbe.blob.core.windows.net/umbraco-assets-corp/5840/transplanting-blood-group-incompatible-kidneys.pdf
No, because Blood group O has no antigens unlike Blood group A2 has A2 antigen and the recipient antibody titer against A2 antigen should be measured and followed
blood group A2 despite being less antigenic ad of less incidence of AMR, yet they still express A2 antigens, unlike blood group O which have no antigens at all being more safe to be considered as a universal donor while blood group A2 is not.
No, blood group A2 is not universal donor
Despite blood group A2 is less antigenic and low immunological risk but still there is risk of AMR.
it’s still need desensitisation protocol and monitoring to anti A2 antibodies in blood but less aggressive monitoring.
it’s need low desensitisation dose to avoid graft loss
1- if the titre is low, transplantation can be proceeded with regular follow up of the titre post-transplantation.
2- if the titre is high, desesnsitization protocols can be applied before transplantation.
Well done. Thank you
. Can we treat blood group A2 as group O, i.e., a universal donor?
No,because blood group O does not have any antigen while blood group type A2 has antigen so there is the risk of sensitization and AMR and we need to measure IgG and IgM titer before proceeding to transplantation.
-The expression of the A2 antigen is weaker than that of the A1 antigen.
– The A2 subtype constitutes approximately 20% of blood type A in white races, while it is only 0.15% in the Japanese population.
-A2 kidney may be less likely to suffer antibody rejection in the presence of anti-A antibodies.
Reference:
Masaki Muramatsu, Hector Daniel Gonzalez et al. ABO incompatible renal transplants: Good or bad?. World J Transplant 2014 March 24; 4(1): 18-29
ISSN 2220-3230 (online)
Well done. Thank you
Blood group antigens have variable immunogenic potential. Blood group A is divided into A1(80%) and A2 -20%. Blood group A1 and B are considered as major and A2 as minor challenge to kidney transplantation . A1 is more immunogenic than B whilst A2 is least immunogenic. As blood group A2 is still immunogenic so antibody titres are expected and should be taken into consideration when planning transplant.
Higher anti A2 titres can lead to AMR and poor outcome. A2 incompatible transplantation is safe in if Anti A2 titres are <16.
Hence it cannot be a universal donor like blood group O.
Reference
Christian Morath et al, ABO-Incompatible Kidney Transplantation. Front Immunol. 06 March 2017
Please see the following Kidney Advisory group document that resonances with responses.
https://nhsbtdbe.blob.core.windows.net/umbraco-assets-corp/5840/transplanting-blood-group-incompatible-kidneys.pdf
thank you
No, We should not regard blood group A2 as a universal donor.
It is known that A2 is less immunogenic than A1, but still the level of anti-A2 antibody titers important in determining the transplantation
The level of ABO antibody titers still important determinant in ABO incompatible transplants.
Anti A2 antibody tires ≤1:16 have good results in graft outcome
High anti A1 IgG antibody titers can lead to AMR and poor graft outcomes.
So, it still need more evidences or study to look at the compatibility to regard as universal donor.
References:
Neetika Garg,Leza Warnke,Robert R. Redfield.Discrepant subtyping of blood type A2 living kidney donors
A. A. R. Tobian, R. S. Shirey, R. A. Montgomery, W. Cai, M. Haas, P. M. Ness, K. E. King. ABO Antibody Titer and Risk of Antibody-Mediated Rejection in ABO-Incompatible Renal Transplantation
American Journal of TransplantationVolume 10, Issue 5 p. 1247-1253
First published: 20 April 2010
https://doi.org/10.1111/j.1600-6143.2010.03103.x
Citations: 82
Yes, agree, well done
Can we treat blood group A2 as group O, i.e., a universal donor?The tissue of the A2 subgroup expressed reduced amount of antigen
compared of Antigen subgroup less reacting with the anti-A1 antibody ,naturally in the serum group O and B recipient.
clinical trials started kidney of A2 subgroup into group O and B recipient with no special pre treatment and standard immunosuoression therapy ,number of graft loss expressed but several long time survival graft .
a few centers have adapted the concepts of A2 to non kidney transplant with successful result when the recipient anti A titre are lower or reduced prior to transplant .
need more trials and studies to know more about the out come of this transplantation and graft survival to reply this question .
references
1-Starzl TE,MarchioroTL,holmeJH,et al.Renalhomo graft in patients with major donor-recipient blood group incompatibilities. surgery 1964,55.195.
Thank you, Dr Manal, agree provided the titre is acceptable, but we can not consider it a universal donor without checking the titre (to me would not be considered a universal donor if I need ti check the titre)
The immunogenic risk determined only by Ag expression is A1>B>A2.
It is possible that A2 will be approved in ABOi because of the minimal immunogenic risk and in order to extend the donor pool, which would lower the time spent on dialysis.
In general, donor A2 kidneys can be safely transplanted into recipients with blood groups B or O if the donor’s anti-A titers are low prior to the transplant but still the risk of AMR is still present.
As a result, blood type A2 cannot be considered a universal donor like blood group O.
–
Neetika Garg,Leza Warnke,Robert R. Redfield.Discrepant subtyping of blood type A2 living kidney donors
Yes, agree, well done
Answer: No
The A2 blood group is expressed at lower levels than A1 and appears to pose a lower barrier to transplantation compared with blood group A1.
A2 kidneys transplanted into O or B recipients may need less pretransplant PEX or IA
However, some studies have suggested that kidneys from A2/A2B donors transplanted into blood group B or O patients who have high titers of A isoagglutinins (anti-A immunoglobulin [Ig]G) can develop rejection and graft loss
A2 donors may be preferable for O or B recipients, they should never the less be treated as fully ABOi transplants
Antibody titers were determined before and after each posttransplant TPE treatment, 72 h after the last planned treatment, at weekly intervals for the first month and at 2, 3, 6 and 12 months.
Reference
1- Bryan, Christopher F.1,8; Winklhofer, Franz T.2; Murillo, Daniel3; Ross, Gilbert4; Nelson, Paul W.5; Shield, Charles F. III6; Warady, Bradley A.7. Improving Access to Kidney Transplantation without Decreasing Graft Survival: Long-Term Outcomes of Blood Group A2/A2B Deceased Donor Kidneys in B Recipients. Transplantation: July 15, 2005 – Volume 80 – Issue 1 – p 75-80
doi: 10.1097/01.TP.0000164288.82238.52.
2-A. A. R. Tobian, R. S. Shirey, R. A. Montgomery, W. Cai, M. Haas, P. M. Ness, K. E. King. ABO Antibody Titer and Risk of Antibody-Mediated Rejection in ABO-Incompatible Renal Transplantation
American Journal of TransplantationVolume 10, Issue 5 p. 1247-1253
First published: 20 April 2010
https://doi.org/10.1111/j.1600-6143.2010.03103.x
Citations: 82
3- Nicholas Torpey, Nadeem E Moghal, Evelyn Watson, and David Talbot. OSH Renal Transplantation. Published online: Oct 2011.
Yes, agree, well done
No still can initiate an immunological response ,only blood group B And O with low anti-
A titers can receive transplant from blood group A2.
Given the longer waiting times of blood type B and O candidates, the allocation of A2
kidneys to select blood group B and O candidates has been studied, demonstrating
significantly reduced wait times to transplant with no significant increase in graft loss or
death .
Ref.
Medline ® Abstract for Reference 22 of ‘Kidney transplantation in adults: ABO
incompatibility.
http://optn.transplant.hrsa.gov/ContentDocuments/OPTN_Policies.pdf.
Yes, agree, well done
According to understanding to the question
yes i can consider the blood group A2 as universal donor such as the blood group o
The ABO subgroup A2 has been reported to be less reactive with the anti-A1 antibody naturally occurring in the serum of group O and B recipients and to occur in approximately 20% of group A individuals We recommend the screening of A donors for the A2 subgroup in both the cadaver-donor and living-related groups, and suggest that the utilization of A2 donors in non-A patients may contribute to the transplantation of group O and highly sensitized patients–and, in some cases, improve the degree of HLA matching
REF:
Successful transplantation of blood group A2 kidneys into non-A recipient
Thank you, Dr Manal, agree provided the titre is acceptable, but we can not consider it a universal donor without checking the titre (to me would not be considered a universal donor if I need ti check the titre)
The ABO blood group consists of four common categories (A, B, AB, and O), with types A and O most frequently found in the United States population. Antigen is expressed on red blood cells, lymphocytes, and platelets, as well as epithelial and endothelial cells. Formation of blood group antibodies occurs against those antigens not native to the host. Thus, antibodies to both A and B are found in an individual with blood type O, while an individual with blood type AB has no antibodies to A or B antigens. Given the distribution of blood group antigens in the United States, the waiting time on the deceased-donor allograft (DDA) list is markedly prolonged for patients with blood group B or O.
Blood group A consists of two subtypes, A1 and A2, or more appropriately “non-A1.” Approximately 80 percent of individuals in the United States with blood group A express A1 The antigenic expression of A2 is quantitatively and qualitatively less than that of A1, and the overall immunogenic risk based on antigen expression alone is A1 >B >A2 . Given the lower immunogenic risk of the A2 antigen, donor A2 kidneys can generally be successfully transplanted into recipients with low pretransplant anti-A titers without the use of desensitization .
Inspite if all this we cannot consider A2 as universal donor however using such donor efficiently can reduce waiting time for many patients
Well done
The basic structure of ABO system is frucosyl galactase H-Ag of O-type blood which present on RBC surface & other tissues. other blood group Ags differ from H-Ag by presence of additional sugar moiety. So blood group can be a universal donor you blood group A2 can’t be universal donor due to presence of these Ags that can lead to immune response activation.
References:
Rahfeld P and Withers S. Toward universal donor blood: Enzymatic conversion of A and B to O type. J.Biol.Chem, 2020; 295(2):325-334.
The writing style and grammar need to be improved, Dr. Ban to deliver the best response.
For the A-blood group specifically there are two phenotypes with different immunogenicity. The A1 phenotype expresses more A epitopes than A2 as the A2 epitope can only be expressed on two of four possible core saccharide chains of the ABO antigen, whereas A1 epitopes can be expressed on all four rendering A2 antigen less immunogenic .Multiple studies concluded that A2 grafts can be safely transplanted into blood group O recipients when ABO-matched grafts are not available indicating that transplantation of A2 kidney or liver grafts was not stopped by high anti-A titers ,also transplanting of A2B-liver grafts to blood group B recipients could have same outcomes of A2-to-O transplantation without the need for induction therapy or maintenance agents. Theoretically, A2-to-B liver transplantation should also be safe.But no enough data was available to confirm those possibilities. (1)
Forbes RC et al concluded that A2i kidney transplantation didnot adversely affect graft or patient survival and it was has been included in the new Kidney AllocationSystem and is considered a favorable option for transplant centers to increase transplant volume and reduce wait times for disadvantaged B waitlist recipients.(2)
Martins PN etal noticed an increase in A2i Deceased Donor Kidney Transplanation among blood group B recipients, in fact the improvement in access for those minorities need to be implicated through the A2/A2B→B component of the new allocation system. In order for A2 incompatible transplantation to be performed and in efforts to increase blood group B access to transplantation among minorities, a protocol for A2 incompatible transplantation need to be done , with standardized assessment of isoagglutinin titers and putting cut points for anti-A titer levels before transplantation.(3)
Meanwhile till now blood group O is the only blood group to be considered as a universal donor
Reference
1-Kluger, Michael D., Guarrera, James V. ,Olsen, Sonja K. , Brown, Robert S. Jr; Emond, Jean C., , Cherqui, Daniel. .Safety of Blood Group A2-to-O Liver Transplantation, Transplantation Journal, 2012 – 94 (5): 526-531
2- Forbes RC, Feurer ID, Shaffer D. A2 incompatible kidney transplantation does not adversely affect graft or patient survival. Clin Transplant. 2016 May;30(5):589-97.
3-Martins PN, Mustian MN, MacLennan PA, Ortiz JA, Akoad M, Caicedo JC, Echeverri GJ, Gray SH, Lopez-Soler RI, Gunasekaran G, Kelly B, Mobley CM, Black SM, Esquivel C, Locke JE. Impact of the new kidney allocation system A2/A2B → B policy on access to transplantation among minority candidates. Am J Transplant. 2
You need to answer the question first.
The immunology concept with liver transplantation is a bit different.
Be specific to the point on future responses.
Despite being less immunogenic than A1 carriers, individuals who have A2 antigens can trigger an immunogenic response and, therefore, could not be universal donors. The only blood group that lacks antigens is group O.
However, with appropriate therapies to minimize the antibodies produced by this antigen, desensitization in this profile should be considered to make it a potential donor.
2. Can we treat blood group A2 as group O, i.e., a universal donor?
Of the 4 main blood types, A, B, AB, & O, only O can be given to any patient (universal donor).
A & B blood differ from the O type in the presence of an additional sugar antigen (GalNAc & Gal, respectively) on the core H-antigen found on O-type RBCs.
So conversion of A, B, & AB RBCs to O-type RBCs could be done by removal of that sugar with an appropriate glycosidase.
New α-galactosidases & α-N-acetylgalactosaminidases were identified in 2007, allowing improved conversion of B & the 1st useful conversions of A-type RBCs.
In 2019, 2 more efficient enzymatic systems, involving a GalNAc deacetylase & a galactosaminidase, for A conversion were discovered.
Removal of the A/B antigens from the donor organ prior to transplant would greatly reduce the need for IS & possibly PP.
Studies have not progressed beyond the use of glycosidases to remove tissue surface antigens from whole organs during perfusion. However the appearance
of improved enzymes and improved perfusion procedures is expected to lead a new hope in this regard.
A2, compared to A1 is less expressed & less immunogenic.
A2 donors have been successfully transplanted into B & A2B recipient. But this cannot be literally considered as a universal donor because there is still the need for IS & PP in this setting.
Reference
J Biol Chem. 2020 Jan 10; 295(2): 325–334.
Published online 2019 Dec 2. doi: 10.1074/jbc.REV119.008164
Be specific to the point
For the timebeing A2 or any other blood group can not be treated as a universal donor; A2 is less expressed and less immunogenic but still would not be considered as universal donor.
But enzymatic manipulation can make such changes in the future.
Can we treat blood group A2 as group O, i.e., a universal donor?
The ABO group consists of four subtypes (A, B, AB, O)
A and O blood groups are the most frequent subtypes in US population, both A and B abs found on blood group O,
Both blood group B and O have prolong waiting list for DDA
A2 phenotype around 10% of US and 8% in black race, 0% in Asia.
The answer is no we cannot consider A2 group as a universal donor like group O, but can be limited for minor ethnic background (African American black with blood group B
A2 incompatible transplantation consider minor donor group with less immunogenicity compared to A1. Minor ABO incompatibility’ from blood group A2 donors into blood group B recipients. This significantly increased the number of such transplants done without desensitization ,also less cost and allow to reduce waiting list without compromise the graft survival (2) should be limited to those with low anti-IgG titer < 1:8 as there is still a risk of post-transplant rebound of anti – IgG antibodies with increased risk of AMR (3).
References:
1-Bryan CF, Winklhofer FT, Murillo D, et al. Improving access to kidney transplantation without decreasing graft survival: long-term outcomes of blood group A2/A2B deceased donor kidneys in B recipients. Transplantation. 2005; 80:75–80
2- Gilbert AJ. Kidney transplantation across minor ABO incompatibility: the use of A2 to B transplants. Curr Opin Organ Transplant. 2019 Aug;24(4):365-369.
3- Williams WW, Cherikh WS, Young CJ, Fan PY, Cheng Y, Distant DA, Bryan CF. First Report on the OPTN National Variance: Allocation of A2 /A2 B Deceased Donor Kidneys to Blood Group B Increases Minority Transplantation. Am J Transplant. 2015 Dec;15(12):3134-42. doi: 10.1111/ajt.13409. Epub 2015 Aug 4. PMID: 26372745.
Excellent response and great insight on how this may increase access to transplantation. Thank you, Dr. Saja
1.Blood group A2 can’t be treated as universal donor,as it has an antigen not like group o,though less immunogenic than other group like A1>B>A2 but still not zero.
Hence A2 titre less than 1/16 is advisable.
Blood group A consists of two subtypes, A1 and A2.
Approximately 80 % of individuals in North America with blood group A express A1.
Antigenic expression of A2 is quantitatively and qualitatively less than that of A1.
Immunogenic risk based on antigen expression alone is A1>B>A2 (1).
We can considered it safe but not as universal donor and it dependent on anti-A2 titers which better to be ≤16.
A2-incompatible transplantation is safe in patients with anti-A2 titers ≤16 with excellent short-term kidney allograft outcomes (2).
A2i kidney transplantation does not adversely affect graft or patient survival (3).
Or can be called semi-compatible.
References:
1-ABO Incompatible Kidney Transplantation (Part 1) lecture, Abu baker Hassan Associate Professor (ASNRT).
2-Azzi Y, Nair G, Loarte-Campos P, et al . A Safe Anti-A2 Titer for a Successful A2 Incompatible Kidney Transplantation: A Single-center Experience and Review of the Literature. Transplant Direct. 2021 Jan 26;7(2):e662. doi: 10.1097/TXD.0000000000001099. PMID: 33521251; PMCID: PMC7837880.
3-Forbes RC, Feurer ID, Shaffer D. A2 incompatible kidney transplantation does not adversely affect graft or patient survival. Clin Transplant 2016; 30:589.
No, we cannot. Although the A2 blood group is less immunogenic, the level of anti A antibody ( IgG ) is important for ABOi transplantation.
Reference:
Tobian AA, Shirey RS, Montgomery RA, Cai W, Haas M, Ness PM, King KE. ABO antibody titer and risk of antibody-mediated rejection in ABO-incompatible renal transplantation. Am J Transplant. 2010 May;10(5):1247-53.
Short response. How this may affect access to transplantation?
It has been widely reported that ABO blood subgroup A2 kidneys have reduced expression of antigen on endothelial surfaces.
A2 kidneys are biologically similar to O kidneys, which means they are more universally accepted by recipients of all blood types, including blood type B.
Many centers have reported their successful experiences with A2 incompatible kidney transplants, most are for blood group B recipients.
Similar success rates for living A2 incompatible transplants to B and O recipients have also been reported.
Patients with blood groups B & O have to wait for a long time to find a blood group compatible donor, so using donors with blood group A2 will shorten their waiting time and expand the donor pool.
However, previous single-centre studies have shown acceptable outcomes for A2 incompatible kidney transplants when the recipient’s pre-transplant anti-A IgG titer is less than or equal to 1:8, so there is a role for Anti-A IgG titer for successful transplantation.
Reference:
Forbes RC, Feurer ID, Shaffer D. A2 incompatible kidney transplantation does not adversely affect graft or patient survival. Clin Transplant 2016: 30: 589–597.
Blood type B and O kidney transplant candidates have the longest wait-times on dialysis.
Subtyping of A and AB donors is important in kidney transplantation because among non-A1 individuals, the A antigenic expression is both quantitatively and qualitatively lower. As a result, kidneys from non-A1 (or non-A1B) donors can be successfully transplanted into blood type B or O recipients (or B) using the same immunosuppression protocols as ABO-compatible transplantation, without desensitization, as long as anti-A titers are low in the recipient at the time of transplantation.
Inaccurate A2 subtyping represents a significant lost opportunity in transplantation, especially in KPD where A2 donors can not only facilitate living donor transplantation for O and highly sensitized candidates, but can also facilitate additional living donor transplants.
Neetika Garg,Leza Warnke,Robert R. Redfield.Discrepant subtyping of blood type A2 living kidney donors: Missed opportunities in kidney transplantation.Clinical TransplantationVolume 35.2021
As A2 is weakly antigenic compared to A1
The incidence of A2 to A1 is 20% in white race
Yet it is 0.15% in Japanese!
This makes titre monitoring mandatory as a decision is taken to go with the Tx.
You are right work up is needed thoroughly so as not to decline potentially good cases.
Case Scenario II
Can we treat blood group A2 as group O, i.e., a universal donor?
Blood group A constitutes 45% of all ABO system, 9% is A2.
Immunogenic risk based on Ag expression alone is A1>B>A2.
A2 may be accepted in ABOi due to low immunogenic risk, but it is not equal to zero.
Exactly so titre monitoring is a must.