Impact of the baseline anti-A/B antibody titer on the clinical outcome in ABO-incompatible kidney transplantation

A2/A2B to B deceased donor kidney transplantation in the Kidney Allocation System era

Kidney transplantation from blood type A2/A2B donors to type B recipients (A2→B) has increased dramatically under the current Kidney Allocation System (KAS). Among living donor transplant recipients, A2-incompatible transplants are associated with an increased risk of all-cause and death-censored graft failure. In light of this, we used data from the Scientific Registry of Transplant Recipients from December 2014 until June 2022 to evaluate the association between A2→B listing and time to deceased donor kidney transplantation (DDKT) and post-DDKT outcomes for A2→B recipients. Among 53 409 type B waitlist registrants, only 12.6% were listed as eligible to accept A2→B offers ("A2-eligible"). The rates of DDKT at 1-, 3-, and 5-years were 32.1%, 61.4%, and 72.1% among A2-eligible candidates and 14.1%, 29.9%, and 44.1% among A2-ineligible candidates, with the former experiencing a 133% higher rate of DDKT (Cox weighted hazard ratio (wHR) = 2.192.332.47; P < .001). The 7-year adjusted mortality was comparable between A2→B and B-ABOc (type B/O donors to B recipients) recipients (wHR 0.780.941.13, P = .5). Moreover, there was no difference between A2→B vs B-ABOc DDKT recipients with regards to death-censored graft failure (wHR 0.771.001.29, P > .9) or all-cause graft loss (wHR 0.820.961.12, P = .6). Following its broader adoption since the implementation of the kidney allocation system, A2→B DDKT appears to be a safe and effective transplant modality for eligible candidates. As such, A2→B listing for eligible type B candidates should be expanded.

Advancement in preoperative desensitization therapy for ABO incompatible kidney transplantation recipients

ABO incompatibility has long been considered an absolute contraindication for kidney transplantation. However, with the increasing number of patients with ESRD in recent years, ABO-incompatible kidney transplantation (ABOi-KT) has expanded the types of donors by crossing the blood group barrier through preoperative desensitization therapy. At present, the desensitization protocols consist of removal of preexisting ABO blood group antibody titers and prevention of ABO blood group antibody return. Studies have suggested similar patient and graft survival among ABOi-KT and ABOc-KT recipients. In this review, we will summarize the effective desensitization regimens of ABOi-KT, aiming to explore effective ways to improve the success rate and the long-term survival rate of ABOi-KT recipients.

Transplant outcomes of 100 cases of living-donor ABO-incompatible kidney transplantation

BACKGROUND

Although ABO-incompatible (ABOi) kidney transplantation (KT) has been performed successfully, a standard preconditioning regimen has not been established. Based on the initial antidonor ABO antibody titers, an individualized preconditioning regimen is developed, and this study explored the efficacy and safety of the regimen.

METHODS

From September 1, 2014, to September 1, 2020, we performed 1668 consecutive living-donor KTs, including 100 ABOi and 1568 ABO-compatible (ABOc) KTs. ABOi KT recipients (KTRs) with a lower antibody titer (≤1:8) were administered oral immunosuppressive drugs (OIs) before KT, while patients with a medium titer (1:16) received OIs plus antibody-removal therapy (plasma exchange/double-filtration plasmapheresis), patients with a higher titer (≥1:32) were in addition received rituximab (Rit). Competing risk analyses were conducted to estimate the cumulative incidence of infection, acute rejection (AR), graft loss, and patient death.

RESULTS

After propensity score analyses, 100 ABOi KTRs and 200 matched ABOc KTRs were selected. There were no significant differences in graft and patient survival between the ABOi and ABOc groups (P  = 0.787, P  = 0.386, respectively). After using the individualized preconditioning regimen, ABOi KTRs showed a similar cumulative incidence of AR (10.0% υs . 10.5%, P  = 0.346). Among the ABOi KTRs, the Rit-free group had a similar cumulative incidence of AR ( P  = 0.714) compared to that of the Rit-treated group. Multivariate competing risk analyses revealed that a Rit-free regimen reduced the risk of infection (HR: 0.31; 95% CI: 0.12-0.78, P  = 0.013). Notably, antibody titer rebound was more common in ABOi KTRs receiving a Rit-free preconditioning regimen ( P  = 0.013) than those receiving Rit. ABOi KTRs with antibody titer rebound had a 2.72-fold risk of AR (HR: 2.72, 95% CI: 1.01-7.31, P  = 0.048). ABOi KTRs had similar serum creatinine and estimated glomerular filtration rate compared to those of ABOc KTRs after the first year.

CONCLUSIONS

An individualized preconditioning regimen can achieve comparable graft and patient survival rates in ABOi KT with ABOc KT. Rit-free preconditioning effectively prevented AR without increasing the risk of infectious events in those with lower initial titers; however, antibody titer rebound should be monitored.

ABO incompatibility in renal transplantation

ABO blood group incompatibility (ABO-I) was historically considered an absolute contraindication to kidney transplantation due to the significant risk of acute antibody-mediated rejection and early graft loss. Nevertheless, the urge to minimize the gap between the candidates’ number on the waitlist for kidney transplants and the available kidney donors encourage investigation into finding ways to use organs from ABO-I kidney donors, especially in the era of using more potent immunosuppression therapies. This review aims to discuss a general overview of ABO-I kidney transplantation and the different protocols adopted by some transplant centers to meaningfully overcome this barrier.

Synergistic impact of pre-sensitization and delayed graft function on allograft rejection in deceased donor kidney transplantation

The aim of this study is to investigate whether or not delayed graft function (DGF) and pre-transplant sensitization have synergistic adverse effects on allograft outcome after deceased donor kidney transplantation (DDKT) using the Korean Organ Transplantation Registry (KOTRY) database, the nationwide prospective cohort. The study included 1359 cases between May 2014 and June 2019. The cases were divided into 4 subgroups according to pre-sensitization and the development of DGF post-transplant [non-pre-sensitized-DGF(−) (n = 1097), non-pre-sensitized-DGF(+) (n = 127), pre-sensitized-DGF(−) (n = 116), and pre-sensitized-DGF(+) (n = 19)]. We compared the incidence of biopsy-proven allograft rejection (BPAR), time-related change in allograft function, allograft or patient survival, and post-transplant complications across 4 subgroups. The incidence of acute antibody-mediated rejection (ABMR) was significantly higher in the pre-sensitized-DGF(+) subgroup than in other 3 subgroups. In addition, multivariable cox regression analysis demonstrated that pre-sensitization combined with DGF is an independent risk factor for the development of acute ABMR (hazard ratio 4.855, 95% confidence interval 1.499–15.727). Moreover, DGF and pre-sensitization showed significant interaction (p-value for interaction = 0.008). Pre-sensitization combined with DGF did not show significant impact on allograft function, and allograft or patient survival. In conclusion, the combination of pre-sensitization and DGF showed significant synergistic interaction on the development of allograft rejection after DDKT.

ABO-incompatible living kidney transplantation

ABO-incompatible living kidney transplantation is nowadays a routine procedure to expand living donor pool. The past decades have seen the evolution of desensitization protocol and immunosuppression regimen. Despite increased bleeding events, infectious complications, and rejection episodes reported in some studies, favorable graft and patient survival rate are now achieved, regardless of various protocols among transplant centers. Several issues such as the usage of rituximab and standardization of blood group antibody titration remain to be settled. The deposition of C4d is no longer the histopathologic hallmark of antibody-mediated rejection, which have inspired innovative strategies of peripheral molecular screening and the improvement of histological diagnosis of AMR (antibody-mediated rejection). The better understanding of the underlying mechanism might facilitate the distinction and therapeutic schemes of AMR.

A case of successful late steroid withdrawal after ABO-incompatible kidney transplantation

Few data exist regarding steroid withdrawal in ABO-incompatible (ABO-i) kidney transplantation (KT). Here, we report a case of steroid withdrawal after ABO-i KT. A 46-year-old man diagnosed with Henoch-Schonlein purpura received ABO-i KT from his 42-year-old sister. The recipient and donor blood types were O and AB, respectively. His preoperative ABO antibody titers were anti-A of 1:16 and anti-B of 1:8 in isoagglutinin test. HLA mismatch was 0 and he received a single 325 mg/m² dose of intravenous (IV) rituximab 4 weeks before KT. Three sessions of plasma exchange were undertaken before KT and low-dose IV immunoglobulin of 0.1 g/kg was administered after plasma exchange. On the day of the operation, ABO antibody titer decreased to anti-A of 1:4 and anti-B of 1:2. Renal function remained stable after KT. The patient wished to stop steroid treatment despite the risk of rejection after withdrawal. Steroid tapering was initiated at 20 months and accomplished at 26 months after KT. At that time, serum creatinine level was 1.13 mg/dL, and anti-A and anti-B titers were 1:8 and 1:2, respectively. No issues were observed after steroid withdrawal. At 48 months after KT, serum creatinine level was 1.21 mg/dL, and anti-A and anti-B antibody titers were 1:32 and 1:2, respectively. Steroid withdrawal in ABO-i KT might be considered in immunologically low-risk patients.

ABO-incompatible heart transplantation in children-a systematic review of current practice

Pediatric heart transplantation has significantly improved in the survival of children with cardiomyopathy and/or complex congenital heart defects. With the increasing number of children needing transplantation, there is a growing demand for the organ, making it harder to cope with the increasing number of children on the waiting list. One of the advances that helped reduce the waiting list mortality significantly is the ability to transplant children from donors with ABO incompatibility. Modification of perfusion abilities and management of donor organ improves outcome in this select population, making ABO-incompatible transplantation an attractive option in the wider armamentarium available for pushing boundaries in these children without impacting on outcomes.

Clinical significance of isoagglutinin titre with the current desensitization protocol in ABO-incompatible kidney transplantation

AIM

ABO-incompatible (ABOi) kidney transplantation (KT) has become a routine procedure with graft survival rates comparable to those of ABO-compatible KT. However, the clinical significance of the isoagglutinin titre in ABOi KT remains uncertain. Therefore, in this study, we analysed the clinical outcomes of ABOi KT according to the baseline and post-operative isoagglutinin titre.

METHODS

All patients who received ABOi KT between 2009 and 2013 were reviewed and followed up until December 2016. The patients were classified according to baseline (<1:128 or ≥1:128) and post-operative rebound isoagglutinin titre (<1:16 or ≥1:16), and the clinical outcomes of KT were compared.

RESULTS

Patients with a high baseline isoagglutinin titre showed a poor titre reduction rate (1.48 ± 0.41 vs 1.32 ± 0.34, P = 0.008), and more patients experienced titre rebound ≥1:16 after KT (15.0% vs 35.8%, P = 0.002). The occurrence of both T-cell-mediated rejection and antibody-mediated rejection did not show a significant difference (P = 0.805 and 0.714, respectively). The rate of rejection-free survival was not different among groups (P = 0.680, log-rank test). Furthermore, the rate of death-censored graft survival was not different among groups (P = 0.701, log-rank test). Urinary tract infection was the most frequently reported infectious complication overall. The incidence of urinary tract infection, pneumonia and viral infections (BK virus and cytomegalovirus) was not different among groups.

CONCLUSION

In conclusion, high baseline isoagglutinin titre was associated with a high rebound isoagglutinin titre, low titre reduction rates and more sessions of plasmapheresis. However, the isoagglutinin titre may not be as important as it was in the past in ABOi KT if appropriate desensitization is performed.

Management of Juvenile Idiopathic Arthritis in ABO-incompatible Kidney Transplantation: A Case Report

Biologic agents are a beneficial therapy for juvenile idiopathic arthritis (JIA). However, there is a lack of evidence with regard to management of these agents for JIA patients who undergo kidney transplantation (KTx). A 36-year-old woman with JIA who was treated with tocilizumab targeting interleukin-6 (IL-6) receptor underwent ABO-incompatible kidney transplantation (ABOi KTx). To prevent over-immunosuppression, tocilizumab was discontinued before ABOi KTx. Rituximab, tacrolimus, mycophenolate mofetil, everolimus, and methylprednisolone were used for immunosuppression. Clinical remission of joint pain was maintained for over 3 years despite complete discontinuation of tocilizumab. Both serum IL-6 and soluble IL-6 receptor levels were markedly decreased, suggesting that multitargeted immunosuppression for ABOi KTx induced long-term clinical remission of JIA through inhibition of the IL-6 pathway. However, levels of C-reactive protein (CRP) and matrix metalloproteinase-3 (MMP-3) gradually increased thereafter and abatacept was initiated to prevent joint deterioration. These levels decreased without any adverse events. The patient's renal graft function was well maintained.

Clinical outcomes of ABO- and HLA-incompatible kidney transplantation: a nationwide cohort study

This was a nationwide cohort study to investigate the impact of anti-A/B and donor-specific anti-HLA (HLA-DSA) antibodies on the clinical outcomes in kidney transplant recipients (KTRs). We classified a total of 1964 KTRs into four groups: transplants from ABO-incompatible donors (ABOi, n = 248); transplants in recipients with HLA-DSA (HLAi, n = 144); transplants from combined ABOi and HLAi donors (ABOi + HLAi, n = 31); and a control group for whom neither ABOi nor HLAi was applicable (CONT, n = 1541). We compared the incidence of biopsy-proven acute rejection (BPAR), allograft and patient survival rates. The incidence of BPAR was higher in the HLAi and ABOi + HLAi groups relative to the CONT group; in contrast, it was not higher in the ABOi group. Death-censored graft survival rates did not differ across the four groups. However, relative to the CONT group, patient survival rate was reduced in the ABOi and ABOi + HLAi groups, and with infection being the most common cause of death. Further, multivariable analysis revealed that desensitization therapy because of ABOi or HLAi was independent risk factors for patient mortality. HLAi was a more important risk factor for BPAR compared with ABOi. However, pretransplant desensitization therapy for either ABOi or HLAi significantly increased the risk of infection-related mortality.

Acquired Downregulation of Donor-Specific Antibody Production After ABO-Incompatible Kidney Transplantation

The mechanism of long-term B cell immunity against donor blood group antigens in recipients who undergo ABO-incompatible (ABOi) living-donor kidney transplantation (LKTx) is unknown. To address this question, we evaluated serial anti-A and anti-B antibody titers in 50 adult recipients. Donor-specific antibody titers remained low (≤1:4) in 42 recipients (84%). However, antibodies against nondonor blood group antigens were continuously produced in recipients with blood type O. We stimulated recipients' peripheral blood mononuclear cells in vitro to investigate whether B cells produced antibodies against donor blood group antigens in the absence of graft adsorption in vivo. Antibodies in cell culture supernatant were measured using specific enzyme-linked immunosorbent assays (ELISAs). Thirty-five healthy volunteers and 57 recipients who underwent ABO-compatible LKTx served as controls. Antibody production in vitro against donor blood group antigens by cells from ABOi LKTx patients was lower than in the control groups. Immunoglobulin deposits were undetectable in biopsies of grafts of eight recipients with low antibody titers (≤1:4) after ABOi LKTx. One patient with blood type A1 who received a second ABOi LKTx from a type B donor did not produce B-specific antibodies. These findings suggest diminished donor-specific antibody production function in the setting of adult ABOi LKTx.

Comparison of clinical outcomes between ABO-compatible and ABO-incompatible spousal donor kidney transplantation

Background

Kidney transplantation (KT) is the treatment of choice for end-stage renal disease patients. The spouse is a major donor in living KT. Clinical outcomes of spousal donor KT are not inferior to those of living related donor KT. In this study, we compared clinical outcomes between ABO-compatible (ABOc) and ABO-incompatible (ABOi) spousal donor KTs.

Methods

Thirty-two cases of spousal donor KT performed from January 2011 to August 2013 were analyzed retrospectively. Twenty-one ABOc KTs and 11 ABOi KTs were performed. We investigated patient survival, graft survival, acute rejection, graft function, and complications.

Results

During follow-up, patient and graft survival rates were 100% in both groups. There were no significant differences in the incidence of delayed graft function, acute rejection, and the change in graft function between the 2 groups. Medical and surgical complications were not significantly different between the groups.

Conclusion

The clinical outcomes of ABOc and ABOi spousal donor KTs were equivalent. In ABOi KT, an emotionally motivated spousal donor KT may be a good alternative to the problem of the absolute shortage of kidney donations.

Excellent long term patient and renal allograft survival after ABO-incompatible kidney transplantation: Experience of one center

AIM: To investigate the long-term results of ABO-incompatible (ABOi) kidney transplantation in a single center in Greece.

METHODS: Thirty consecutive ABOi kidney transplantations were performed from June 2005 to December 2013. All patients received rituximab one month prior to transplantation. Immunoadsorption therapy was performed for the removal of anti-A/B IgG antibodies until the titer was ≤ 1:16. Additional apheresis sessions were performed post-operatively. Intravenous immunoglobulin and oral immunosuppression consisting of tacrolimus (TAC) in combination with either everolimus or mycophenolate acid was administered. We compared the long term results of our ABOi group to those of a matched group of 30 ABO compatible (ABOc) living kidney recipients with similar baseline characteristics. The ABOc recipients received an immunosuppressive regimen consisting of TAC and mycophenolate acid. All patients in both groups received induction therapy with Basiliximab or Daclizumab, whereas corticosteroids were instituted on the day of surgery. During the follow-up period, indication biopsies were performed and interpreted by an experienced nephropathologist. The parameters we analyzed included the following: Donor/recipient age, gender, blood type, human leukocyte antigen mismatches, panel reactive antibodies, primary cause of renal failure, mean time on dialysis, immunosuppressive regimen, patient survival, graft outcome, incidence of rejections, surgical and infectious complications.

RESULTS: The mean follow-up period was 6 years (range 1 to 9 years). A mean of 5.0 ± 3.0 (range 0-14) pre-transplant immunoadsorptions were required in order to reach the target titer. Patient survival in ABOi group in comparison to ABOc group at 1, 3, 5 and 8 years did not differ significantly (100% vs 100%, 96% vs 100%, 92% vs 100% and 92% vs 100%, P = ns). Additionally, graft survival was similar in the two groups at the same time points (100% vs 100%, 96% vs 96%, 92% vs 96% and 81% vs 92%, P = ns). The mean serum creatinine and the estimated glomerular filtration rate by the modification of diet in renal disease formula at 1, 3, 5 and 8 years did not differ significantly between ABOi and ABOc group. None of the patients in the ABOi group developed acute or chronic antibody-mediated rejection evidenced by histological signs. Four patients (13.3%) in the ABOi group and 3 (10%) in the ABOc group experienced acute cellular rejection, which was treated successfully in all cases. Bacterial and viral infections were also similar between the two groups.

CONCLUSION: ABOi kidney transplantation is a safe and effective alternative that enables kidney transplantation in countries with unacceptably long deceased-donor waiting lists.

Postoperative rebound of antiblood type antibodies and antibody-mediated rejection after ABO-incompatible living-related kidney transplantation

The purpose of this study is to examine whether postoperative antiblood type antibody rebound is attributed to kidney allograft rejection in ABO blood type-incompatible (ABO-I) living-related kidney transplantation (KTx). A total of 191 ABO-I recipients who received ABO-I living-related KTx between 2001 and 2013 were divided into two groups: Group 1 consisted of low rebound [(≦1:32), N = 170] and Group 2 consisted of high rebound [(≧1:64), N = 21], according to the levels of the rebounded antiblood type antibodies within 1 year after transplantation. No prophylactic treatment for rejection was administered for elevated antiblood type antibodies, regardless of the levels of the rebounded antibodies. Within 1 year after transplantation, T-cell-mediated rejection was observed in 13 of 170 recipients (13/170, 8%) in Group 1 and in 2 of 21 recipients (2/21, 10%) in Group 2 (Groups 1 vs. 2, P = 0.432). Antibody-mediated rejection was observed in 15 of 170 recipients (15/170, 9%) and 2 of 21 recipients (2/21, 10%) in Groups 1 and 2, respectively (P = 0.898). In this study, we found no correlation between the postoperative antiblood type antibody rebound and the incidence of acute rejection. We concluded that no treatment is necessary for rebounded antiblood type antibodies.

Impact of ABO Incompatibility on the Development of Acute Antibody-Mediated Rejection in Kidney Transplant Recipients Presensitized to HLA

Whether the coexistence of anti-A/B antibody and donor specific anti-HLA antibody (HLA-DSA) has a synergistic impact on the development of acute antibody-mediated rejection (AAMR) in kidney transplant recipients (KTRs) is unclear. This study includes 92 KTRs who received a kidney from an ABO-incompatible (ABOi) donor or were presensitized to donor HLA (HLAs) and 292 controls (CONT). HLAs was defined as a crossmatch positivity or the presence of HLA-DSA. We compared the incidence of AAMR among ABOi (n = 58), ABOi+HLAs (n = 12), HLAs (n = 22), and CONT (n = 292) groups and evaluated the risk factors and antibody type (anti-A/B vs. HLA-DSA) responsible for AAMR. AAMR developed less frequently in ABOi and CONT than in the ABOi+HLAs or HLAs (P < 0.05 for all); however, there was no difference between the ABOi+HLAs and HLAs groups. AAMR developed more frequently with strong HLA-DSA at baseline; however, high baseline anti-A/B titer did not affect AAMR development. Strong baseline HLA-DSA was an independent predictor for AAMR, however the baseline anti-A/B titer was not. All four AAMR episodes in ABOi+HLAs were positive to HLA-DSA but not to anti-A/B. In conclusion, ABO incompatibility does not increase the risk for AAMR in HLAs KTRs.