A new concept of accommodation in ABO-incompatible kidney transplantation

Strategies for ABO Incompatible Liver Transplantation

Liver transplantation (LT) is a definitive treatment for the decompensated liver cirrhosis and fulminant liver failure. With limited availability of cadaveric liver allograft, ABO incompatible (ABOi) living donor liver transplantation (LDLT) plays an important part in further expansion of donor pool. Over the years, with the introduction of Rituximab and improving desensitisation protocol, outcomes of ABOi LDLT are on par with ABO compatible LT. However, ABOi LDLT protocol varies markedly from centre to centre. Intravenous Rituximab followed by plasmapheresis or immunoadsorption effectively reduce ABO isoagglutinins titre before transplant, thereby reducing the risk of antibody mediated rejection in the post-transplant period. Local infusion therapy and splenectomy are not used routinely at most of the centres in Rituximab era. Post-transplant immunosuppression usually consists of standard triple drug regime, and tacrolimus trough levels are targeted at higher level compared to ABO compatible LT. Introduction of newer therapies like Belatacept and Obinutuzumab hold promise to further improve outcomes and reduce the risk of antibody mediated rejection related complications. ABOi LT in emergency situations like acute liver failure and deceased donor LT is challenging due to limited time period for desensitisation protocol before transplant, and available evidence are still limited but encouraging.

Ex vivo enzymatic treatment converts blood type A donor lungs into universal blood type lungs

Donor organ allocation is dependent on ABO matching, restricting the opportunity for some patients to receive a life-saving transplant. The enzymes FpGalNAc deacetylase and FpGalactosaminidase, used in combination, have been described to effectively convert group A (ABO-A) red blood cells (RBCs) to group O (ABO-O). Here, we study the safety and preclinical efficacy of using these enzymes to remove A antigen (A-Ag) from human donor lungs using ex vivo lung perfusion (EVLP). First, the ability of these enzymes to remove A-Ag in organ perfusate solutions was examined on five human ABO-A1 RBC samples and three human aortae after static incubation. The enzymes removed greater than 99 and 90% A-Ag from RBCs and aortae, respectively, at concentrations as low as 1 μg/ml. Eight ABO-A1 human lungs were then treated by EVLP. Baseline analyses of A-Ag in lungs revealed expression predominantly in the endothelial and epithelial cells. EVLP of lungs with enzyme-containing perfusate removed over 97% of endothelial A-Ag within 4 hours. No treatment-related acute lung toxicity was observed. An ABO-incompatible transplant was then simulated with an ex vivo model of antibody-mediated rejection using ABO-O plasma as the surrogate for the recipient circulation using three donor lungs. The treatment of donor lungs minimized antibody binding, complement deposition, and antibody-mediated injury as compared with control lungs. These results show that depletion of donor lung A-Ag can be achieved with EVLP treatment. This strategy has the potential to expand ABO-incompatible lung transplantation and lead to improvements in fairness of organ allocation.

Complement activation and long-term graft function in ABO-incompatible kidney transplantation

BACKGROUND

ABO-incompatible and ABO-compatible kidney transplantation are equivalent in terms of short-term graft and patient survival. This is thought to be the result of ABO-incompatible graft accommodation, which occurs when anti-blood group antibodies re-occur after transplantation but somehow do not yield their detrimental effect. The underlying mechanism is unclear, but one of the hypotheses is that this is the result of complement inhibition. Since virtually all ABO-incompatible graft biopsies are C4d positive, this complement inhibition must occur somewhere in the complement cascade after the formation of C4d has already taken place, but where exactly is unclear. It is also unclear whether complement inhibition is complete. Incomplete accommodation could explain why recent studies have shown that long-term graft function in ABO-incompatible transplantation is somewhat inferior to ABO-compatible kidney transplantation.

AIM

To unravel the relationship between pre-transplant anti-ABO antibodies, complement activation, and long-term graft function.

METHODS

We included all 27 ABO-incompatible transplantations that were performed between 2008 and 2013 at the Academic Medical Center Amsterdam and the University Medical Center Groningen. For each ABO-incompatible transplantation, we included four ABO-compatible controls matched by age, sex, and transplantation date.

RESULTS

Graft and patient survival were not significantly different. The slope of kidney function during five-year follow-up was also not significantly different, but ABO-incompatible recipients did have a lower kidney function at three months (creatinine clearance 58 vs 69 mL/min, P = 0.02, Modification of Diet in Renal Disease 46 vs 52 mL/min/1.73 m², P = 0.08), due to a high rate of early rejection (33% vs 15%, P = 0.03), mostly T-cell mediated. Pre-transplant anti-ABO IgG titers were positively correlated with C5b-9 staining, which itself was positively correlated with the occurrence of T-cell mediated rejection. This may be the result of concurrent C5a formation, which could function as a costimulatory signal for T-cell activation.

CONCLUSION

Co-stimulation of T-cell activation by ongoing complement activation by anti-ABO antibodies may be responsible for an impaired long-term graft function in ABO-incompatible kidney transplantation.

Repeat A2 Into B Kidney Transplantation After Failed Prior A2 Into B Transplant: A Case Report

Kidneys from donors with blood type A2 can be successfully transplanted into blood type B and O recipients without the need for desensitization if the recipient's starting anti-A hemagglutinin titer is within an acceptable range. National kidney allocation policy now offers priority for eligible B recipients to receive A2 or A2B deceased donor kidneys, and therefore, the frequency with which A2 or A2B to B transplants will occur is expected to increase. The precise mechanisms by which antibody-mediated rejection is averted in these cases despite the presence of both circulating anti-A antibody and expression of the A2 antigen on the graft endothelium are not known. Whether this process mirrors proposed mechanisms of accommodation, which can occur in recipients of ABO incompatible transplants, is also not known. Repeated exposure to mismatched antigens after retransplantation could elicit memory responses resulting in antibody rebound and accelerated antibody-mediated rejection. Whether this would occur in the setting of repeated A2 donor exposure was uncertain. Here we report the case of a patient with history of a prior A2 to B transplant which failed owing to nonimmunologic reasons; the patient successfully underwent a repeat A2 to B transplant. Neither rebound in anti-A2 antibody nor clinical evidence of antibody-mediated rejection were observed after the transplant. Current kidney allocation will likely enable more such transplants in the future, and this may provide a unique patient population in whom the molecular mechanisms of incompatible graft accommodation may be investigated.

Effects of Neutralization by Soluble ABH Antigens Produced by Transplanted Kidneys From ABO-Incompatible Secretor Donors

BACKGROUND

Grafts survive despite blood group antigens on the transplant being continuously exposed to antibodies in the blood of recipients in ABO-incompatible kidney transplantation (ABOi KT), owing to the mechanism of accommodation. We analyzed the immunodynamics of soluble ABH antigens in allografts from secretor donors and the influence of such immunodynamics on accommodation and subsequent graft survival in ABOi KT.

METHODS

The genotype of a known human β-galactoside α-1,2-fucosyltransferase gene (FUT2), which determines soluble ABH antigen secretor status, was established in 32 donors for ABOi KT at the Severance Hospital, from June 2010 to July 2015. Clinical outcomes of recipients, such as anti-A/B antibody titer change, renal function, and graft survival, were evaluated.

RESULTS

Twenty-five donors were secretors (78.1%), and seven were nonsecretors (21.9%). The frequency of anti-A/B IgG or IgM antibody titer elevation or reduction post-transplantation was not significantly related to donor secretor status. However, IgM titer was rapidly reduced in recipients transplanted from nonsecretor donors (P=0.01), which could be explained by the lack of absorption effect of soluble antigens, enhancing the binding of antibodies to antigens in the allografts. Interestingly, soluble ABH antigens did not affect rejection-free graft survival, which may be due to the nature of β-galactoside α-1,2-fucosyltransferase.

CONCLUSIONS

Soluble ABH antigens produced by transplanted kidneys from secretor donors played a role in inducing accommodation within three months of KT through neutralization; however, major graft outcomes were not affected.

Reviewing the pathogenesis of antibody-mediated rejection and renal graft pathology after kidney transplantation

The clinicopathological context of rejection after kidney transplantation was well recognized. Banff conferences greatly contributed to elucidate the pathogenesis and to establish the pathologic criteria of rejection after kidney transplantation. The most important current problem of renal transplantation is de novo donor-specific antibody (DSA) production leading chronic rejection and graft loss. Microvascular inflammation is considered as a reliable pathological marker for antibody-mediated rejection (AMR) in the presence of DSA. Electron microscopic study allowed us to evaluate early changes in peritubular capillaries in T-lymphocyte mediated rejection and transition to antibody-mediated rejection. Severe endothelial injuries with edema and activated lymphocyte invaded into subendothelial space with early multi-layering of peritubular capillary basement membrane suggest T-lymphocyte mediated rejection induce an unbounded chain of antibody-mediated rejection. The risk factors of AMR after ABO-incompatible kidney transplantation are important issues. Anti-ABO blood type antibody titre of IgG excess 32-fold before transplant operation is the only predictable factor for acute AMR. Characteristics of chronic active antibody-mediated rejection (CAAMR) are one of the most important problems. Light microscopic findings and C4d stain of peritubular capillary and glomerular capillary are useful diagnostic criteria of CAAMR. Microvascular inflammation, double contour of glomerular capillary and thickening of peritubular capillary basement are good predictive factors of the presence of de novo DSA. C4d stain of linear glomerular capillary is a more sensitive marker for CAAMR than positive C4d of peritubular capillary. Early and sensitive diagnostic attempts of diagnosing CAAMR are pivotal to prevent chronic graft failure.

The Role of Liver Sinusoidal Endothelial Cells in Induction of Carbohydrate Reactive B Cells Tolerance Through the Programmed Death 1/Programmed Death Ligand 1 Pathway

BACKGROUND

A spontaneous tolerance of B cells responding to blood group antigens frequently develops in ABO-incompatible pediatric liver transplantation (LT). Liver sinusoidal endothelial cells (LSECs), which exclusively express blood group antigens in the liver, possess a capacity to induce alloantigen-specific tolerance. In this study, we elucidated the role of LSECs in the tolerance induction of blood group antigen-reactive B cells after ABO-incompatible LT using mice that lack galactose-α(1,3)galactose (Gal) epitopes resembling blood group carbohydrate antigens.

METHODS

Using adoptive transfer of LSECs from wild type (WT) C57BL/6J mice to congenic α1,3-galactosyltransferase gene knockout (GalT) mice, we established orthotropic GalT → GalT LSEC chimera mice. Anti-Gal Ab (antibody) production was evaluated after immunization of GalT → GalT LSEC chimera mice with Gal rabbit RBC.

RESULTS

Adoptive transfer of LSECs isolated from WT GalT mice via the portal vein resulted in persistent engraftment of Gal LSECs in congenic GalT mouse livers. Only when GalT mice were splenectomized before LSEC inoculation, the GalT → GalT LSEC chimera lost the ability to produce anti-Gal Abs. The administration of blocking monoclonal Abs (mAbs) against programmed death ligand 1 to the splenectomized GalT → GalT LSEC chimera resulted in the recovery of anti-Gal Ab production.

CONCLUSIONS

These findings suggest that LSECs take a part in tolerization of immature but not mature B cells specifically for Gal. Furthermore, the programmed death 1/programmed death ligand 1 pathway likely plays a crucial role in the mechanisms underlying spontaneous tolerization of B cells responding to ABO-blood group antigens in LT.

Complement Interception Across Humoral Incompatibility in Solid Organ Transplantation: A Clinical Perspective

The humoral barrier in transplant biology is the result of preformed donor-specific antibodies (DSAs), directed either against human leukocyte antigens (HLA) or non-HLA antigens such as blood group (ABO) molecules. The term "sensitization" applies to patients carrying these antibodies. Transplantation is widely accepted as a life-saving opportunity for patients with terminal end-organ disease. However, in sensitized patients, transplant outcome is hampered by antibody-mediated rejection (AMR) as a consequence of DSA exposure. Furthermore, sensitized patients have limited access to "matched" organs from the both living and deceased donor pool.Considering the crucial role of the complement system in the pathophysiology of AMR and the availability of complement intervention therapeutics, there is a growing interest in complement-targeting strategies. This review highlights the emerging importance of monitoring and modulation of the complement system in the context of enabling transplantation across humoral incompatibility in sensitized recipients with preformed anti-HLA or natural anti-ABO antibodies. It also discusses the significance of the complement system in the induction of accommodation and further emphasizes current and future perspectives of novel complement therapeutics.

Kinetics of B, T, NK lymphocytes and isoagglutinin titers in ABO incompatible living donor liver transplantation using rituximab and basiliximab

BACKGROUND

The kinetics of isoagglutinin titers and lymphocyte subpopulations including B, T, and natural killer (NK) cells after ABO incompatible (ABO-I) living donor liver transplantation (LDLT) have not been evaluated.

METHODS

From January 2012 to July 2013, consecutive ABO-I LDLT patients were enrolled at the National Cancer Center. Our desensitizing protocol included rituximab, plasma exchanges, basiliximab, and intravenous immune globulin without splenectomy.

RESULTS

Twenty patients (14 males, 6 females) underwent ABO-I LDLT due to HCC (n=15) or liver cirrhosis (n=5). There was no hyperacute and antibody-mediated rejection. The isoagglutinin titers were effectively lowered less than 1:16 before operation. CD 19+ B cells were rapidly eliminated after rituximab and suppressed during 6months postoperatively. CD3+ and CD4+ T cells were elevated higher than CD8+ T cells. CD4/CD8 ratio was increased during first 1month postoperatively and decreased thereafter. CD16+CD56+ NK cells were lowered and restored after 4months of LDLT. Among 15 patients with HCC, 5 patients (33.3%) experienced early tumor recurrence (1/8 within Milan and 4/7 beyond Milan).

CONCLUSIONS

Our protocol showed effective results in preventing antibody-mediated rejection and suppressing B lymphocytes. Application to advanced hepatocellular carcinoma should be considered due to decreased natural immunity after ABO-I LDLT.

Blood group antigen-targeting peptide suppresses anti-blood group antibody binding to antigen in renal glomerular capillaries after ABO-incompatible blood reperfusion

BACKGROUND

Antibody-mediated rejection after ABO-incompatible kidney transplantation (ABO-I KTx) is a major barrier to transplantation success. The advent of immunosuppressive therapy has markedly improved graft survival in ABO-I KTx. However, compared with normal KTx, clinical conditions during ABO-I KTx are difficult to control because of overimmunosuppression. To reduce the need for immunosuppression, we aimed to develop a novel blood group antigen-neutralizing therapy.

METHODS

We screened for an ABO blood group antigen-targeting peptide (BATP) by screening of T7 phage-displayed peptide library. After screening, hemagglutination inhibition assays, enzyme-linked immunosorbent assay, and cytotoxicity assay were used to analyze the blood group antigen-blocking effect and toxicity of BATP. We also tested the inhibitory effects on anti-blood group antibody binding in normal human kidney tissues blocked with BATP and excised kidneys perfused ex vivo with BATP.

RESULTS

We identified six peptide sequences that efficiently suppressed hemagglutination of red blood cells by anti-ABO blood group antibodies and binding of these antibodies to ABO histo-blood group antigens in kidney tissues. Surprisingly, ex vivo perfusion of BATP in kidneys excised from renal cell carcinoma patients caused significant suppression of anti-blood group antibody binding to antigen and IgG and IgM deposition in renal glomerular capillaries after ABO-I blood reperfusion.

CONCLUSIONS

These data indicate that A/B blood group antigens on red blood cells and in kidney tissues may be neutralized by BATP. This approach may enable the development of a novel blood group antigen-neutralizing therapy to overcome the challenges of ABO-I KTx.

Anti-H can trigger apoptosis and down-regulate FUT1 expression in erythroid differentiated K562 cells without complement mediation

The reason why delayed RBC engraftment and pure red cell aplasia (PRCA) develop only in some but not all recipients of major ABO-incompatible hematopoietic stem cell transplantation (HSCT) remains elusive and the underlying mechanisms are not fully understood. Understanding how incompatible erythroid blood group antibodies (Abs) interact with ABH antigens (Ags) of grafts, and investigating how to induce artificially accommodation of grafts are of obvious importance in transplantation immunology. The effects of anti-H on proliferation, apoptosis, and α-(1,2)-fucosyltransferase gene (FUT1) expression in erythroid differentiated K562 cells were analyzed by the MTT assay, Annexin V/PI staining, and quantitative RT-PCR method. The growth of erythroid differentiated K562 cells was significantly suppressed when anti-H dilution was ≤ 1:8 (P<0.001, as compared with 1:16). Under the complement-free culture conditions, the apoptotic ratio of erythroid differentiated K562 cells was significantly increased when anti-H dilution was ≤ 1:16 (P<0.05, as compared with 1:32). The apoptosis was not only closely associated with anti-H dilution (F=138.991, P<0.001), but also correlated with treated time (F=583.249, P<0.001), which indicated typical dose- and time-dependent effects. Under the complement-free culture conditions, the FUT1 mRNA expression level was also suppressed when anti-H dilution was ≤ 1:16 (P<0.05, as compared with 1:32), which also manifested in typical dose-dependent (F=130.356, P<0.001) and time-dependent (F=1432.00, P<0.001) effects. The results confirm that anti-H can trigger apoptosis and down-regulate FUT1 expression in erythroid differentiated K562 cells without complement mediation. The findings suggest that anti-H could accommodate grafts through triggering apoptosis and down-regulating Fut1 expression to reduce ABH antigens.

Selective capture of anti-A antibodies from human blood using a novel integrated bead and hollow fiber module

Anti-A/B antibody removal from blood in the peritransplantation period facilitates ABO-incompatible transplantation and significantly increases the donor pool. We have been developing an anti-A/B immunoadsorption device (BSAF), compatible with whole blood perfusion. The BSAF is based on integrated microfiltration hollow fibers with antibody capturing beads uniformly distributed within the fiber interstitial space. In this study we fabricated BSAF prototypes, appropriately scaled down from a conceptual clinical scale device. We then, for the first time, measured the time course of anti-A capture from blood samples recirculating through the scaled down BSAF devices. We observed a significant reduction in IgM (96% ± 5%, n = 5, p < 0.001), and IgG (81% ± 18%, n = 5, p < 0.05) anti-A antibody titers within 2 h. We did not observe a significant change between the initial and final values of hematocrit, total plasma protein concentration, plasma free hemoglobin concentration, and anti-B antibody titer over five experiments. In conclusion we showed that the BSAF modules selectively removed anti-A antibodies from blood in a simple one step process, without requiring a separate plasmapheresis unit.

ABO-incompatible kidney transplantation

Owing to the shortage of deceased donors in Japan, since 1989, we have performed ABO-incompatible kidney transplantation (ABO-IKTx) to expand the indication for living donor kidney transplantation. During the past two decades, about 2000 ABO-IKTxs were performed. Since 2001 the success rate for these kidney transplants has reached 96% for 1-year, 91% for 5-year and 83% for 9-year graft survival, similar to outcomes of ABO-compatible kidney transplantation (ABO-CKTx). This dramatic improvement in results means that ABO-IKTx has become accepted as a therapeutic alternative for end-stage renal failure. Today ABO-IKTx accounts for approximately 30% of all living donor kidney transplantations performed in Japan. We have been making a lot of efforts to elucidate the mechanism of acute antibody-mediated rejection in ABOI-KTx in order to overcome the ABO barrier and to improve the outcome. From careful and precise clinical observations, proteomic analysis of ABO histo-blood group antigens in graft endothelial cells and deep insight into immunology and biology, we have reached the hypothesis that the structural difference of ABO histo-blood group antigens and de novo corresponding antibody production would be the key and keyhole of the development of acute AMR in ABOI-KTx. Preoperative desensitization therapy would be the best solution for the suppression of acute AMR and graft loss, which is now widespread and improves the outcome.

Long-term recurrence-free survival after liver transplantation from an ABO-incompatible living donor for treatment of hepatocellular carcinoma exceeding Milano criteria in a patient with hepatitis B virus cirrhosis: a case report

The early results of liver transplantations (OLT) in patients with advanced hepatocellular carcinoma (HCC) were poor because of frequent tumor recurrence. However, OLT has significant, theoretical advantage that it removes both the tumor and the organ that is at a risk of malignancy. The Japanese law on organ transplantation limited the availability of cadaveric liver donors until its revision on July 17, 2011. ABO-incompatible OLT was formerly contraindicated because performed anti-A/B antibodies on recipient endothelial cells raised the risk of antibody-mediated humoral graft rejection. We have herein described four successful cases of steroid withdrawal among adult patients who underwent living donor OLT from ABO-incompatible donors. In addition, we transplanted a liver from a living donor into an ABO-incompatible recipient on August 9, 2004. The 55-year-old man with HCC due to hepatitis B virus (HBV) a cirrhosis had a Child-Pugh score of C, and Model for End-stage Liver Disease score of 22. Two tumors greater than 5 cm, exceeded the Milan criteria. His des-gamma-carboxy prothrombin level was 6 mAu/mL, and alpha-fetoprotein, 18.78 ng/mL. Antirejection therapy included multiple perioperative plasmaphereses and splenectomy; with an immunosuppressive regimen consisting of tacrolimus, methylprednisolone, and mycophenolate mofetil. The maintenance dose of immunosuppression did not differ from that of ABO-identical cases. After transplantation, we used intrahepatic arterial infusion therapy with prostaglandin E1 (PG E1). The patient had complications of portal vein thrombosis, hepatic artery thrombosis, and acute myocardial infarction, which were treated by interventional radiology in the posttransplantation period. We controlled the HBsAb titer by administering hepatitis B immunoglobulin and lamivudine (200 IU/L doses) for 1 year after OLT and 100 IU/L doses thereafter. As a result, the patient achieved long-term, disease-free graft survival without steroids. He currently has good liver function and leads a normal lifestyle. Our results suggested the feasibility of controlling antibody-mediated humoral rejection and other complications in living donor liver transplantations into ABO-incompatible adults via intrahepatic arterial PG E1 infusion splenectomy, and plasmapheresis with regular immunosuppression. Withdrawal of steroids, HBV vaccination, and lamivudine, an nucleoside analog reverse transcriptase inhibitor, have achieved long-term (7 years) survival without recurrent HBV infection or tumor.

Desensitization with antigen-specific immunoadsorption interferes with complement in ABO-incompatible kidney transplantation

BACKGROUND

Complement activation was characterized during and after desensitization treatment in 19 consecutive patients receiving ABO-incompatible (ABOi) living donor kidney transplants to assess the effect of desensitization protocol including antigen-specific immunoadsorption (IA) on complement activation.

METHODS

All patients received rituximab- and tacrolimus-based triple treatment. Anti-A/B antibodies were removed by IA. Serial determinations of C3, C3a, the C3a/C3 ratio, and sC5b-9 were carried out between day -30 and postoperative day 30. C1q was measured on day -30 and the day before the transplantation. In two recipients, eluates from immunoadsorbent columns were analyzed for C3a, C1q, and immunoglobulins by western blotting. Same complement analysis was performed in eluate from a control column after in vitro perfusion of AB-plasma.

RESULTS

Patient and graft survival were 100% for a median follow-up of 40 months (range, 12-60 months). There were no humoral rejections based on ABO-antigen-antibody interactions. C3a and the C3a/C3 ratio declined with the start of IA treatment, and this decline was maintained postoperatively. C1q declined from day -30 to a lower value on the day before transplantation (P<0.05). In eluates from both patient and control, immunoadsorbent column immunoglobulins together with C3a and C1q were detected.

CONCLUSIONS

The current protocol including antigen-specific IA interferes with the complement system; this effect may be partially responsible for the absence of humoral rejection resulting from ABO-antigen-antibody interactions and the excellent outcomes obtained after ABO-incompatible kidney transplantation.

ABO Incompatible Kidney Transplantation-Current Status and Uncertainties

In the past, ABO blood group incompatibility was considered an absolute contraindication for kidney transplantation. Progress in defined desensitization practice and immunologic understanding has allowed increasingly successful ABO incompatible transplantation during recent years. This paper focused on the history, disserted outcomes, desensitization modalities and protocols, posttransplant immunologic surveillance, and antibody-mediated rejection in transplantation with an ABO incompatible kidney allograft. The mechanism underlying accommodation and antibody-mediated injury was also described.

Short-term results of ABO-incompatible living donor kidney transplantation: comparison with ABO-compatible grafts

Purpose

ABO incompatible (ABOi) kidney transplantation (KT) has been increasing to compensate for the shortage of organ donors. However, detailed comparative analyses of ABOi KT with ABO compatible (ABOc) KT are still rare.

Methods

This retrospective study compared 12 consecutive ABOi KTs to 50 ABOc KTs that employed the same maintenance immunosuppressive agents during the same period. Comparisons of patient survival, graft survival, graft function, and complications were made until post-transplant day 90.

Results

Baseline characteristics of the two groups were similar except for the positivity of panel reactive antibody (12% in the ABOc group vs. 42% in the ABOi group; P = 0.029). There were no significant differences in patient survival, graft survival, post-operative renal function, incidence of acute rejection, infections, or medical and surgical complications. However, bleeding complications were more common in the ABOi group (25%) than versus the ABOc group (6%) (P = 0.08). The preoperative and total hospital stay of the ABOi patients was significantly longer than the ABOc patients (P = 0.001).

Conclusion

ABOi KT is a viable and safe option for patients whose only donor is blood incompatible, despite the longer preoperative hospital stay for preparation.

Prompt reversal of a severe complement activation by eculizumab in a patient undergoing intentional ABO-incompatible pancreas and kidney transplantation

We describe the presumably first intentional ABO-incompatible deceased-donor kidney and pancreas transplantation with a severe antibody-mediated rejection during a rebound of isoagglutinins. Rejection was successfully treated with eculizumab, which inhibits the terminal pathway of complement. Complement analysis (C3, C3d,g, and a modified assay of classical complement-related hemolytic function) documented complement activation and confirmed that eculizumab completely blocked complement function. At 6 months, the patient had normal kidney and pancreas function, and histological evaluations revealed no evidence of sustained graft damage. This successful transplantation suggests that ABO barriers can safely be overcome without extensive preconditioning, when the complement inhibitor eculizumab is included.

Correlation between insulin requirements and anti-galactose antibodies in patients with type 1 diabetes transplanted with neonatal pig islets

Pig xenografts represent an alternative source of organs for transplantation. Immunosuppression can prevent rejection, but involves high risk and cost. New anti-rejection techniques have been developed; however, results have not been successful. Few studies have reported xenoantibody levels in xenotransplanted patients with diabetes and no patients have reported a clinical correlation. We analysed anti-galactose (Gal) and other anti-pig antibody (APA) levels in xenotransplanted patients with type 1 diabetes and the relation to the clinical outcome. Twenty-three patients with type 1 diabetes were transplanted with porcine islets inside a device without immunosuppression. Demographic characteristics, insulin dose and xenoantibody levels at different periods were recorded. Anti-Gal and anti-pig antibodies were measured through indirect enzyme-linked immunosorbent assay (ELISA) and haemolytic anti-pig antibody assay. More than 50% were female; the mean current age, current diabetes duration, diabetes duration at xenotransplantation and time post-transplantation were: 20·8, 11, 5·5 and 5·7 years, respectively. Insulin doses remained with a mean reduction greater than 33% in more than 50% of the patients. The lowest anti-Gal antibody levels were related to the highest insulin dose reductions. This relationship could be explained by the device, Sertoli cells and accommodation process.

Current progress in ABO-incompatible liver transplantation

BACKGROUND

ABO-incompatible (ABOi) living donor liver transplantation (LDLT) in adult patients has been controversial because of the high risk of antibody-mediated rejection (AMR) mediated by preformed anti-ABO antibodies. However, outcomes have recently improved owing to various treatment advances.

MATERIALS AND METHODS

This review article describes the history and current progress in ABOi liver transplantation, mainly from the viewpoint of the Japanese experience.

RESULTS

The typical clinical manifestations of AMR are hepatic necrosis and intrahepatic biliary complication. The outcomes of early ABOi LDLT were poor, especially in older children and adult cases. Since we first introduced portal vein infusion therapy into adult ABOi LDLT in 1998, local graft infusion therapy has emerged in Japan as a crucial breakthrough to overcome the ABO blood group barrier. From 2003, rituximab prophylaxis has been widely used with local graft infusion, and has resulted in markedly improved patient survival. The novel approach of intravenous immunoglobulin induction may become another option to suppress AMR. Continued patient enrollment and controlled trials will allow further validation of these treatments.

CONCLUSIONS

The outcome of ABOi LDLT is now similar to that of blood-type-matched transplantation in Japan. However, infection is the major cause of morbidity and mortality after ABOi LDLT. Thus, evaluation of the patients' immune status and adjustment of immunosuppression will be the way forward in the future.

Therapeutic plasma exchange for desensitization prior to transplantation in ABO-incompatible renal allografts

BACKGROUND

Although there have been desensitization protocols used for ABO-incompatible (ABOi) renal transplants, there are a lack of studied protocols. Our center developed a preconditioning protocol that involved mycophenolic acid, therapeutic plasma exchange (TPE), anti-CD20 monoclonal antibody (rituximab), and intravenous immunoglobulin (IVIG) that allowed for ABOi renal transplantation.

METHODS

Ten patients in our institution with end-stage renal disease who were unable to procure ABO-compatible donor kidneys underwent treatment with this protocol (which included a uniform 5 TPE sessions) prior to an ABOi renal transplant. A retrospective chart review was performed on these patients and clinical endpoints including ABO antibody titers, serum creatinine, clinical complications, and graft performance were analyzed.

RESULTS

The median ABO antibody titers at presentation, after completion of the protocol, and after transplant for the patients were 32 (range, 2-128), 8 (range, 1-64), and 4 (range, 2-32), respectively. The mean serum creatinine at study conclusion was 1.45 +/- 1.04 mg/dl at an average of 262.20 days from transplant. There were four incidents of antibody-mediated rejection (AMR) and two incidents of delayed graft function (DGF). There was one incident of graft failure and no patient deaths.

CONCLUSIONS

The desensitization protocol used by our institution allowed for successful ABOi renal transplantation. Although there were incidents of AMR and DGF, the majority of the transplants resulted in viable grafts. A larger patient study group may be needed to fully evaluate the efficacy and safety of this protocol.

ABO-incompatible adult living donor liver transplantation for hepatocellular carcinoma

Living donor liver transplantation (LDLT) offers timely transplantation for patients with hepatocellular carcinoma (HCC). If ABO-incompatible LDLT is feasible, the need for pretransplantation treatment may be eliminated, which may reduce overall morbidity. In this article, we have described 8 adult HCC patients who successfully underwent LDLT from ABO-incompatible donors. Antirejection therapy included multiple preoperative plasmaphereses, splenectomy, and an immunosuppressive regimen with tacrolimus, methylprednisolone, and mycophenolate mofetil. The maintenance dose of immunosuppression did not differ from that of the ABO-identical cases. In addition, we also performed intrahepatic arterial infusion of prostaglandin E1. In 5 patients, we administered a single dose of rituximab, a chimeric CD20 monoclonal antibody. As a result of this treatment, 6/8 patients are still alive. Our experience has shown that it is possible to control antibody-mediated humoral rejection and other complications in adult ABO-incompatible LDLT.

Removal of blood group A/B antigen in organs by ex vivo and in vivo administration of endo-beta-galactosidase (ABase) for ABO-incompatible transplantation

BACKGROUND

ABO incompatibility in organ transplantation is still a high risk factor for antibody-mediated rejection, despite the progress in effective treatments. We have explored the possibility of using the enzyme to remove the blood type A/B antigen in organs.

METHODS

Recombinant endo-beta-galactosidase (ABase), which releases A/B antigen, was produced in E. coli BL-21. Human A/B red blood cells (RBC) were digested with ABase, and subjected to flow cytometric analysis after incubation with human sera. Purified recombinant ABase was intravenously administered to a baboon. Biopsies were taken from kidney and liver before and 1, 4 and 24 h after in vivo administration. Excised baboon kidneys were perfused with cold UW solution+/-purified recombinant ABase and preserved at 4 degrees C. Biopsies were taken before and 1 and 4 h after ex vivo perfusion. The change in A/B antigen expression was analyzed by immunohistochemical study.

RESULTS

ABase removed 82% of A antigen and 95% of B antigen in human A/B red blood cells, and suppressed anti-A/B antibody binding and complement activation effectively. ABase was also found to remain active at 4 degrees C. In vivo infusion of ABase into a blood type A baboon demonstrated a marked reduction of A antigen expression in the glomeruli of kidney (85% at 1 h, 9% at 4 h and 13% at 24 h) and the sinusoids of liver (47% at 1 h, 1% at 4 h and 3% at 24 h) without serious adverse effects. After ex vivo perfusion and cold storage of excised baboon kidney (blood type B) with ABase, the expression levels of B antigen in glomeruli were reduced to 49% at 1 h and 6% at 4 h.

CONCLUSIONS

This alternative approach might be useful for minimizing antibody removal and anti-B cell immunosuppression as an adjuvant therapy in ABO-incompatible kidney, liver and possibly heart transplantation.

Long-term follow-up ABO-incompatible adult living donor liver transplantation in cirrhotic patients

ABO-incompatible liver transplantation is usually contraindicated. The presence in the recipient of preformed anti-A/B antibodies located on endothelial cells raises the risk of antibody-mediated humoral rejection of the graft. We describe four successful cases of steroid withdrawal in adult patients who had living-donor liver transplantation from ABO-incompatible donors. Antirejection therapy included multiple perioperative plasmapheresis, splenectomy, and a triple immunosuppressive regimen with tacrolimus, methylprednisolone (MPSL), and cyclophosphamide or mycophenolate mofetil (MMF). The maintenance dose of immunosuppression did not differ from that of ABO-identical cases. After transplantation, intrahepatic arterial infusion therapy with prostaglandin E1 (PG E1) was used. As a result, all four patients were able to achieve long-term graft survival without steroid use. They all have good liver function and are leading normal lifestyles. Our experience with these four patients suggests the feasibility of controlling humoral rejection and other complications in adult ABO-incompatible living donor liver transplantations with intrahepatic arterial infusion of PGE1, splenectomy, and plasmapheresis with a regular base of immunosuppression protocol to prevent antibody-mediated humoral rejection.

Recent findings in ABO-incompatible kidney transplantation: classification and therapeutic strategy for acute antibody-mediated rejection due to ABO-blood-group-related antigens during the critical period preceding the establishment of accommodation

In Japan, ABO-incompatible kidney transplantation has been performed in more than 1000 patients since 1989, and recently accounts for about 18% of all living donor kidney transplants. As for outcomes, since 2001 the 1-year and 3-year graft survival rates have increased to 96% and 94%, respectively, which are similar to those in ABO-compatible transplantation. These improved outcomes are attributed to a clearer understanding of the mechanisms underlying accommodation and acute antibody-mediated rejection, permitting the development of new therapeutic strategies. This review classifies and discusses the clinical significance of acute antibody-mediated rejection due to ABO-blood-group-related antigens during the critical period preceding the establishment of accommodation.

Unexpected immunoresponse to Gal and APA antigens in diabetic type 1 patients receiving neonatal pig islets after 6 years

Cotransplantation of porcine islets and Sertoli cells into preimplanted subcutaneous devices improve metabolic control in type 1 diabetic patients, and survive grafted for more than 4 years. We report here, further assessment of the endocrine and porcine nature of the surviving cells and the immune responses elicited toward Gal alpha(1,3)-Gal beta(1,4)-GlcNAc (Gal) antigen in patients who received a second and third transplants. No immunosuppressive drugs were administered. We were able to immunostain insulin- and glucagon-positive cells in all biopsies of patients and Sertoli cell markers in 60.9% of biopsies. Additionally, all biopsies tested, amplified the porcine COII gene. Patients demonstrated an increase in antipig antibodies in response to the first transplant with a decreasing response toward the second and third transplants. In all transplants, the IgG levels promptly returned to basal values after 3-4 months. The long-term survival of porcine cells and the reduced humoral immune response to multiple transplants indicate a form of tolerance. We have not been able to find CD25-positive cells, indicating that it is probably an immune accommodation of the graft.

Development of a Novel ELISA for Detection of Anti-A and Anti-B Antibodies in Recipients of ABO-Incompatible Living Donor Liver Grafts

The survival rate in ABO-incompatible (ABO-I) liver transplantation was much lower than that in ABO-compatible recipients for the early experiences. It is therefore essential to develop the precise and fast measurement of anti-A and anti-B antibodies (Abs) to prevent humoral rejection in ABO-I liver transplantation. Agglutination titer has been the standard method to measure these Abs, but the interpretation of the results is subject to bias. Here, we have developed an objective and quantitative enzyme-linked immunosorbent assay (ELISA) to measure anti-A and anti-B Abs. This test requires only a small amount (10 microl) of recipient's serum. We applied the newly developed ELISA to monitor living donor liver transplant recipients and investigated the correlation between ELISA and agglutination titer. The Spearman's correlation coefficient for Abs ranged from 0.461 to 0.812. Moreover, in one case of humoral rejection, the increase of Abs was detected by ELISA one day earlier than by the agglutination titer. In conclusion, our ELISA method proved useful to detect an increase of anti-A and anti-B Abs titers at an early stage, thereby contributing to a prompt treatment of humoral rejection due to ABO-I.

ABO incompatible kidney transplantation - an analysis of UNOS Registry data

BACKGROUND

The ABO incompatible kidney transplants have been performed successfully from large numbers of living donors and some blood type A2 deceased donors. However, there are few reports to support the feasibility of ABO incompatible transplants from non-A2 deceased donors. This problem was examined in the United Network for Organ Sharing (UNOS) data file.

PATIENTS AND METHODS

The UNOS Registry data of kidney transplants performed between 1995 and 2003 from 256 centers was utilized for Kaplan-Meier curves and log-rank tests to compare graft and functional graft survival rates.

RESULTS

Deceased donor transplants from all ABO incompatible donors had the same graft survival rates, as that from ABO compatible donors regardless of whether the blood group incompatibility was A (A1), A2 or B. Graft survival from 201 ABO incompatible donors was 66.9% at 5 yr, compared with 66.7% for ABO compatible donors (p = 0.83). Non-A2 incompatible donors also yielded comparable survival rates to ABO compatible donors. From living donors, ABO incompatible donors yielded significantly lower graft survival rates than the ABO compatible group, although long-term graft survival rates of those who survived >1 yr did not differ significantly.

CONCLUSION

Except higher initial graft loss possibility because of insufficient removal of antibodies, non-A2 kidneys yielded equivalent graft survival rates to ABO compatible transplants. In addition to A2 incompatibilities, Blood group A1 and B incompatibilities can also be considered in ABO incompatible transplants.

Pinpoint targeted immunosuppression: anti-CD20/MMF desensitization with anti-CD25 in successful ABO-incompatible kidney transplantation without splenectomy

BACKGROUND

In Japan, ABO-incompatible (ABO-I) kidney transplantation began in 1989; these transplantations have flourished because of the lack of cadaveric donors, and more than 600 cases were performed up to 2004. Splenectomy has been considered to be necessary for successful ABO-I kidney transplantation, and the majority of pre-conditioning protocols include splenectomy in Japan. However, we have lost some grafts due to antibody-mediated rejection (AMR) accompanying explosive elevation of anti-A/B antibody (Ab) titer even though the patients had a low pre-operative Ab titer.

PATIENTS AND METHODS

We utilized two doses of anti-CD20, rituximab, simply combined with mycophenolate mofetil (MMF)/low-dose steroid desensitization started 1 month before surgery in ABO-I kidney transplantation. Two sessions of pre-operative Ab removal by double filtration plasmapheresis or plasma exchange were carried out. We performed six ABO-I kidney transplantations without splenectomy. Anti-A/B Ab titers were more than 16 to 32 times before treatment. We did not plan any post-operative repeated Ab removal or intravenous immunoglobulin G (IVIG).

RESULTS

Pre-operative anti-A/B Ab titers were successfully reduced to less than eight times in all cases. Except for one case in which we had to remove the graft due to aspiration pneumonia and methicillin-resistant staphylococcus epidermidis (MRSE) sepsis, the other five cases did not experience antibody-mediated rejection (AMR). An additional session of post-operative Ab removal and/or IVIG was not necessary. In all patients, B cells (CD19+, CD20+, CD21+) and activated T cells (CD25+) were selectively suppressed, although CD3+, CD4+ and CD8+ cell populations remained stable, thus we call our protocol "pinpoint targeted immunosuppression." Plasma immunoglobulin level was also successfully suppressed, especially after 6 weeks of surgery.

CONCLUSION

Anti-CD20/MMF desensitization is safe and allows successful ABO-I kidney transplantation without splenectomy.

Present status of ABO-incompatible kidney transplantation in Japan

BACKGROUND

We have been making continuous efforts in ABO-incompatible kidney transplantation since 1989 to expand the opportunities for kidney transplantation from living donors in Japan.

PATIENTS AND METHOD

From the Japanese registry, we reviewed the long-term patient and graft survival of ABO-incompatible kidney transplantation. This survey focused on 564 patients who received ABO-incompatible kidney grafts from January 1989 to December 2003 in whom monitoring follow-up could be achieved in 60 institutions all over Japan. The mean age of 367 (65%) male and 197 (35%) female patients at surgery was 34.5 yr. Pre-operative anti-A/B antibody (Ab) removal and splenectomy (n = 553, 98%) were routinely performed combined with triple or quadruple immunosuppression using calcinurine inhibitor (CNI), anti-metabolites and steroids with or without deoxyspurgualin (DSG) or anti-lymphocyte Abs.

RESULTS

The overall patient survival rate at 1, 3, 5 and 10 yr after transplantation was 94, 91, 88 and 81%, with overall graft survival rates of 86, 82, 74 and 53%, respectively. The graft survival rate was significantly higher in patients aged 29 and younger compared with those aged 30 and older. Children aged 15 or younger in particular have shown excellent graft survival rates at 1, 3, 5 and 10 yr of 90, 90, 86 and 76%, respectively. Patients with anticoagulation therapy (n = 285) showed a significantly higher graft survival rate than those without anticoagulation (n = 213), with 10-yr graft survival rates of 59 vs. 48%. There were no significant differences between A and B incompatibility with respect to clinical outcomes. There were also no significant difference in numbers of human leukocyte antigen mismatches, induction and maintenance CNI (cyclosporin A (CYA) vs. tacrolimus) and donor/recipient relationships with respect to the outcomes. We divided the patients into five groups according to the transplanted year periods. The outcome of the most recent 124 cases since 2001 had dramatically improved, with 2-yr graft survival of 94%, and there is a significant difference between the groups in 2001 onwards and the other four groups.

CONCLUSION

This study confirms that the long-term outcome of ABO-incompatible living kidney transplantation is excellent and is similar to that of ABO-compatible cases. Recent data show that short-term graft survival has also improved. ABO-incompatible kidney transplantation is a radical, but safe and effective, treatment choice for end-stage renal disease.