Histologic findings of antibody-mediated rejection in ABO blood-group-incompatible living-donor kidney transplantation

Enzymatic conversion of human blood group A kidneys to universal blood group O

ABO blood group compatibility restrictions present the first barrier to donor-recipient matching in kidney transplantation. Here, we present the use of two enzymes, FpGalNAc deacetylase and FpGalactosaminidase, from the bacterium Flavonifractor plautii to enzymatically convert blood group A antigens from the renal vasculature of human kidneys to 'universal' O-type. Using normothermic machine perfusion (NMP) and hypothermic machine perfusion (HMP) strategies, we demonstrate blood group A antigen loss of approximately 80% in as little as 2 h NMP and HMP. Furthermore, we show that treated kidneys do not bind circulating anti-A antibodies in an ex vivo model of ABO-incompatible transplantation and do not activate the classical complement pathway. This strategy presents a solution to the donor organ shortage crisis with the potential for direct clinical translation to reduce waiting times for patients with end stage renal disease.

Acute antibody-mediated rejection limited to medullary lesions in following ABO-incompatible living donor kidney transplantation

Anatomical differences between the renal cortex and medulla may influence inflammatory responses. Owing to the difficulty in diagnosing rejections from the medulla, rejection is usually diagnosed through the cortex. However, previous studies have shown that there are no significant differences in renal cortical and medullary lesions in acute allograft rejection. A 60-year-old man with a history of diabetic nephropathy underwent kidney transplant from a living unrelated donor at our hospital in August 2019. Three days after surgery, his urine output suddenly decreased, whereas the serum creatinine levels increased. A kidney biopsy showed only medullary lesions with positive C4d-staining and a Banff score of PTC grade 3. He was diagnosed with acute antibody-mediated rejection (AMR) and treatment was initiated. He did not respond to conventional treatments, including plasma exchange and intravenous immunoglobulin, but his general condition improved after bortezomib administration. There have been a few cases of acute AMR limited to medullary lesions. We consider that rejection cannot be excluded even if the lesions are confined to the medulla.

A Safe Anti-A2 Titer for a Successful A2 Incompatible Kidney Transplantation: A Single-center Experience and Review of the Literature

Background.

Kidney allocation system allows blood type B candidates accept kidneys from A2/A2B donors. There is no mandate by UNOS on which the anti-A2 level is acceptable. We aimed to investigate the safety of kidney transplant in blood group B patients with anti-A2 titers ≤16.

Methods.

We performed 41 A2-incompatible kidney transplants in blood group B recipients between May 2015 and September 2019. Clinical outcomes were compared with a control group of 75 blood group B recipients who received blood group compatible kidney transplantation at the same period.

Results.

Of the 41 recipients, 85% were male, 48% African American, with a median age of 53 (20–73) y. Thirty-eight (93%) were deceased-donor and 3 (7%) were living-donor kidney transplant recipients. Pretransplant anti-A2 IgG titers were 2 in 16, 4 in 9, 8 in 6, and 16 in 5 and too weak to titer in 5 recipients. Eight patients had pretransplant donor-specific antibodies. During a median follow-up of 32.6 mo (6–57.3) patient and graft survival were 100% and 92% in the A2-incompatible kidney transplant group, and 91% and 92% in the blood group compatible group, respectively. Twelve A2-incompatible recipients underwent a 21 clinically indicated kidney biopsies at a median 28 d (6–390) after transplantation. None of the patients developed acute antibody-mediated rejection and 2 patients (5%) had acute T-cell–mediated rejection. Interestingly, peritubular capillary C4d positivity was seen in 7 biopsies which did not have any findings of acute rejection or microvascular inflammation but not in any of the rejection-free biopsies in the control group. C4d positivity was persistent in 5 of those patients who had follow-up biopsies.

Conclusions.

A2-incompatible transplantation is safe in patients with anti-A2 titers ≤16 with excellent short-term kidney allograft outcomes. C4d positivity is frequent in allograft biopsies without acute rejection.

Analysis of the prevalence of systemic de novo thrombotic microangiopathy after ABO-incompatible kidney transplantation and the associated risk factors

OBJECTIVES

To analyze the prevalence of systemic de novo thrombotic microangiopathy in ABO-incompatible kidney transplantation and risk factors associated with this condition.

METHODS

A total of 201 patients who received living-donor kidney transplantation (114 patients with ABO-identical kidney transplantation and 87 patients with ABO-incompatible kidney transplantation) were retrospectively analyzed. Systemic de novo thrombotic microangiopathy was diagnosed clinically according to the presence of thrombocytopenia with microangiopathic hemolytic anemia and pathological findings of thrombotic microangiopathy. Anti-A and anti-B antibodies were purified from human plasma, and these antibodies' bindings to human kidney were investigated in vitro.

RESULTS

ABO-incompatible kidney transplantation was a significant risk factor of systemic de novo thrombotic microangiopathy (odds ratio 55.9, 95% CI 1.8-8.9, P < 0.001) after transplantation. Multivariate logistic regression analysis showed that non-use of mycophenolate mofetil, pretreatment immunoglobulin G antibody titer ≥64-fold and pretransplant immunoglobulin M antibody titer ≥16-fold were significant risk factors for systemic de novo thrombotic microangiopathy in ABO-incompatible kidney transplantation. Microvascular inflammation of 1-h post-transplant biopsy could be observed more frequently in thrombotic microangiopathy patients than in non-thrombotic microangiopathy patients. Anti-A and anti-B antibodies purified from human plasma showed a strong in vitro reaction against human kidney when the antibody titer was ≥16-fold.

CONCLUSIONS

Antibody titer should be decreased to ≤16-fold until the day of ABO-incompatible kidney transplantation by desensitization therapy including mycophenolate mofetil. The 1-h biopsy results might help to diagnose systemic de novo thrombotic microangiopathy.

Evaluation of Microvascular Inflammation in ABO-Incompatible Kidney Transplantation

BACKGROUND

In ABO-incompatible kidney transplantation, the diagnostic criteria for antibody-mediated rejection remain controversial because C4d deposition is commonly observed. Thus, we investigated microvascular inflammation (MVI score ≥ 2) within 1 year as a predictor of graft outcome.

METHODS

A total of 148 recipients without preformed or de novo donor-specific anti-HLA antibody were stratified based on MVI score less than 2 (n = 117) and MVI score of 2 or greater (n = 31).

RESULTS

We found that 5-year graft survival was significantly lower (P = 0.0129) in patients with MVI (89.8%) than in patients without MVI (97.0%). Graft function, as characterized by serum estimated glomerular filtration rate, was also significantly worse for patients with MVI than it was for patients without MVI, between 3 months and 10 years after transplantation (P = 0.048). Multivariate analysis indicated that HLA class II mismatch (P = 0.0085) was an independent marker of MVI.

CONCLUSIONS

Microvascular inflammation score of 2 or greater is significantly associated with poor graft outcome after ABO-incompatible kidney transplantation. We suggest that MVI score of 2 or greater in ABOi transplantation be used as a basis to diagnose antibody-mediated rejection.

Current status of pediatric renal transplant pathology

Histopathology is still an indispensable tool for the diagnosis of kidney transplant dysfunction in adult and pediatric patients. This review presents consolidated knowledge, recent developments and future prospects on the biopsy procedure, the diagnostic work-up, classification schemes, the histopathology of rejection, including antibody-mediated forms, ABO-incompatible transplants, protocol biopsies, recurrent and de novo disease, post-transplant lymphoproliferative disorder, infectious complications and drug-induced toxicity. It is acknowledged that frequently the correct diagnosis can only be reached in consensus with clinical, serological, immunogenetical, bacteriological and virological findings. This review shall enhance the understanding of the pediatric nephrologist for the thought processes of nephropathologists with the aim to facilitate teamwork between these specialist groups for the benefit of the patient.

Thrombalexins: Cell-Localized Inhibition of Thrombin and Its Effects in a Model of High-Risk Renal Transplantation

Allograft transplantation into sensitized recipients with antidonor antibodies results in accelerated antibody-mediated rejection (AMR), complement activation, and graft thrombosis. We have developed a membrane-localizing technology of wide applicability that enables therapeutic agents, including anticoagulants, to bind to cell surfaces and protect the donor endothelium. We describe here how this technology has been applied to thrombin inhibitors to generate a novel class of drugs termed thrombalexins (TLNs). Using a rat model of hyperacute rejection, we investigated the potential of one such inhibitor (thrombalexin-1 [TLN-1]) to prevent acute antibody-mediated thrombosis in the donor organ. TLN-1 alone was able to reduce intragraft thrombosis and significantly delay rejection. The results confirm a pivotal role for thrombin in AMR in vivo. This approach targets donor organs rather than the recipient and is intended to be directly translatable to clinical use.

Current progress in ABO-incompatible kidney transplantation

ABO-incompatible kidney transplantation (ABOi KT) was introduced to expand the donor pool and minimize shortage of kidneys for transplantation. Because improved outcomes of ABOi KT were reported in Japan in the early 2000s, the number of ABOi KTs has been increasing worldwide. In addition, a better understanding of immune pathogenesis and subsequent aggressive immunosuppression has helped to make effective desensitization protocols. Current strategies of ABOi KT consist of pretransplant antibody removal using plasmapheresis or immunoadsorption to prevent hyperacute rejection and potent maintenance immunosuppression, such as tacrolimus and mycophenolate mofetil, to inhibit antibody-mediated rejection. Recent outcomes of ABOi KT are comparable with ABO-compatible KT. However, there are still many problems to be resolved. Very high anti-ABO antibody producers are difficult to desensitize. In addition, ABOi KT is associated with an increased risk of infection and possibly malignancy due to aggressive immunosuppression. Optimization of desensitization and patient-tailored immunosuppression protocols are needed to achieve better outcomes of ABOi KT. This review provides an overview of the history, immune mechanism, immunosuppressive protocol, outcomes, current obstacles, and future perspectives in ABOi KT.

Optimizing HLA matching in a highly sensitized pediatric patient using ABO-incompatible and paired exchange kidney transplantation

BACKGROUND

Kidney transplantation is the treatment of choice for end-stage renal disease. However, since pediatric patients have long projected life-years, it is also optimal for them to get well-matched transplants to minimize long-term sensitization. In North America, pediatric kidney transplantation is largely dependent upon the use of deceased donor organs, making it challenging to identify timely, well-matched transplants. Pediatric recipients may have willing living donors who are either HLA- or ABO-incompatible (ABOi); therefore, one solution is to utilize ABOi transplants and paired exchange programs to enhance HLA matching and living donation.

CASE-DIAGNOSIS/TREATMENT

We adopted this approach for a highly sensitized patient with cPRA 90%, who received a successful ABOi paired exchange transplant. The recipient received pre-transplant immunomodulation until an acceptable isohemagglutinin titer <1:8 was reached before transplantation. The patient was induced with anti-thymocyte globulin and maintained on steroid-based triple immunosuppression. Eighteen-month allograft function is excellent with an estimated glomerular filtration rate (eGFR) of 83.53 ml/min/1.73 m(2). The patient did not develop de novo donor-specific HLA antibodies or have any episodes of acute rejection

CONCLUSIONS

This case highlights the safety and efficacy of using paired exchange in combination with ABOi transplants in pediatric kidney transplantation to optimize HLA matching, minimize wait times, and enhance allograft survival.

Quantifying renal allograft loss following early antibody-mediated rejection

Unlike antibody-mediated rejection (AMR) with clinical features, it remains unclear whether subclinical AMR should be treated, as its effect on allograft loss is unknown. It is also uncertain if AMR's effect is homogeneous across donor (deceased/live) and (HLA/ABO) antibody types. We compared 219 patients with AMR (77 subclinical, 142 clinical) to controls matched on HLA/ABO-compatibility, donor type, prior transplant, panel reactive antibody (PRA), age and year. One and 5-year graft survival in subclinical AMR was 95.9% and 75.7%, compared to 96.8% and 88.4% in matched controls (p = 0.0097). Subclinical AMR was independently associated with a 2.15-fold increased risk of graft loss (95% CI: 1.19-3.91; p = 0.012) compared to matched controls, but not different from clinical AMR (p = 0.13). Fifty three point two percent of subclinical AMR patients were treated with plasmapheresis within 3 days of their AMR-defining biopsy. Treated subclinical AMR patients had no difference in graft loss compared to matched controls (HR 1.73; 95% CI: 0.73-4.05; p = 0.21), but untreated subclinical AMR patients did (HR 3.34; 95% CI: 1.37-8.11; p = 0.008). AMR's effect on graft loss was heterogeneous when stratified by compatible deceased donor (HR = 4.73; 95% CI: 1.57-14.26; p = 0.006), HLA-incompatible deceased donor (HR = 2.39; 95% CI: 1.10-5.19; p = 0.028), compatible live donor (no AMR patients experienced graft loss), ABO-incompatible live donor (HR = 6.13; 95% CI: 0.55-67.70; p = 0.14) and HLA-incompatible live donor (HR = 6.29; 95% CI: 3.81-10.39; p < 0.001) transplant. Subclinical AMR substantially increases graft loss, and treatment seems warranted.

Desensitization with plasmapheresis and anti-Cd20 for ABO incompatible kidney transplantation from living donor: experience of a single center in Italy

OBJECTIVE

Blood group incompatibility in kidney transplants from a living donor can be successfully overcome by using various desensitization protocols: intravenous immunoglobulin, plasmapheresis (PP), immunoadsorption, and double filtration PP.

PATIENTS AND METHODS

From July 2010 to October 2013, we performed 10 ABO incompatible kidney transplantation (KT) procedures from a living donor. The desensitization protocol was based on rituximab and PP+cytomegalovirus immune globulin. All patients received induction with basiliximab, except 1 case treated with Thymoglobuline® (ATG) for the simultaneous presence of donor-specific antibody. Tacrolimus and mycophenolate mofetil were initiated at the time of desensitization and continued after the transplant.

RESULTS

After a mean follow-up of 11.6±10.4 months, all patients are alive with a functioning graft. The mean serum creatinine concentration at 1 month, 3 months, 6 months, and 1 year was 1.48±0.29, 1.47±0.18, 1.47±0.27, and 1.5±0.27 mg/dl. Three episodes of acute cellular rejection occurred in 2 patients. There was only 1 case of BK virus infection, treated with reduction of immunosuppressive therapy. The protocol biopsy specimens at 1, 3, and 6 months were C4d positive in the absence of acute rejection.

CONCLUSIONS

Desensitization with rituximab, PP, and anti-cytomegalovirus immune globulin allowed us to perform transplants from living donors to ABO incompatible recipients with excellent results and reduced costs.

Use of belatacept to maintain adequate early immunosuppression in calcineurin-mediated microangiopathic hemolysis post-renal transplant

We report a 17-yr-old boy who developed a microangiopathic hemolytic anemia presumed secondary to tacrolimus shortly following a living-related donor renal transplant. This was initially managed by plasmapheresis. Reinstitution of calcineurin inhibition using cyclosporine led to recurrence of hemolysis, so an alternative agent was needed. He was commenced on monthly intravenous belatacept, with no further recurrence of the hemolysis, and subsequent stable graft function. Modulation via CTLA-4 offers an alternative immunosuppressive tactic if current regimens produce graft threatening adverse effects. The method of administration and frequency of dosage of belatacept also lends itself well to the high-risk period of adolescence and transition. We propose that belatacept may therefore also have utility in difficult cases complicated by poor concordance, common in the adolescent age group.

Impact of donor-specific antibodies in reconstructive transplantation

For many devastating injuries and tissue defects where conventional reconstruction is not possible, reconstructive transplantation such as hand and face transplantation has become a viable alternative. This novel approach allows for improved restoration of appearance, anatomy and function not feasible by other available treatment options. However, clinical management of these injuries prior to transplantation frequently requires multiple blood transfusion or skin grafts resulting in the formation of alloantibodies (anti-HLA IgG Abs) and a high degree of sensitization. The role of donor-specific antibodies (DSA) and mechanisms of antibody-mediated rejection (AMR) in reconstructive transplantation are still largely unknown. Thus there is an imminent need to develop a better understanding of the mechanisms related to DSA and AMR after reconstructive transplantation. In this review, we will define the role of DSA and mechanisms of AMR in reconstructive transplantation and compare them to established measures and treatment concepts in solid organ transplantation.

Late antibody-mediated rejection after ABO-incompatible kidney transplantation during Gram-negative sepsis

Background

The major challenge in ABO-incompatible transplantation is to minimize antibody-mediated rejection. Effective reduction of the anti-ABO blood group antibodies at the time of transplantation has made ABO-incompatible kidney transplantation a growing practice in our hospital and in centers worldwide. ABO antibodies result from contact with A- and B-like antigens in the intestines via nutrients and bacteria. We demonstrate a patient with fulminant antibody-mediated rejection late after ABO-incompatible kidney transplantation, whose anti-A antibody titers rose dramatically following Serratia marcescens sepsis.

Case presentation

A 58-year-old woman underwent an ABO-incompatible kidney transplantation for end-stage renal disease secondary to autosomal dominant polycystic kidney disease. It concerned a blood group A1 to O donation. Pre-desensitization titers were 64 for anti-blood group A IgM and 32 for anti-blood group A IgG titers. Desensitization treatment consisted of rituximab, tacrolimus, mycophenolate mofetil, corticosteroids, immunoadsorption and intravenous immunoglobulines. She was readmitted to our hospital 11 weeks after transplantation for S. marcescens urosepsis. Her anti-A IgM titer rose to >5000 and she developed a fulminant antibody-mediated rejection.

We hypothesized that the (overwhelming) presence in the blood of S. marcescens stimulated anti-A antibody formation, as S. marcescens might share epitopes with blood group A antigen. Unfortunately we could not demonstrate interaction between blood group A and S. marcescens in incubation experiments.

Conclusion

Two features of this post-transplant course are remarkably different from other reports of acute rejection in ABO-incompatible kidney transplantation: first, the late occurrence 12 weeks after kidney transplantation and second, the very high anti-A IgM titers (>5000), suggesting recent boosting of anti-A antibody formation by S. marcescens.

The First Fifty ABO Blood Group Incompatible Kidney Transplantations: The Rotterdam Experience

This study describes the single center experience and long-term results of ABOi kidney transplantation using a pretransplantation protocol involving immunoadsorption combined with rituximab, intravenous immunoglobulins, and triple immune suppression. Fifty patients received an ABOi kidney transplant in the period from 2006 to 2012 with a follow-up of at least one year. Eleven antibody mediated rejections were noted of which 5 were mixed antibody and cellular mediated rejections. Nine cellular mediated rejections were recorded. Two grafts were lost due to rejection in the first year. One-year graft survival of the ABOi grafts was comparable to 100 matched ABO compatible renal grafts, 96% versus 99%. At 5-year follow-up, the graft survival was 90% in the ABOi versus 97% in the control group. Posttransplantation immunoadsorption was not an essential part of the protocol and no association was found between antibody titers and subsequent graft rejection. Steroids could be withdrawn safely 3 months after transplantation. Adverse events specifically related to the ABOi protocol were not observed. The currently used ABOi protocol shows good short and midterm results despite a high rate of antibody mediated rejections in the first years after the start of the program.

Role of plasma exchange in ABO-incompatible kidney transplantation

Background

In the past, ABO incompatibility was an absolute contraindication for solid organ transplantation. However, multiple recent trials have suggested strategies for overcoming the reactions between graft antigens and recipient antibodies that cause graft rejection. In this study, we determined the usefulness of plasma exchange (PE) for removing anti-A/B antibodies that cause hyperacute/acute humoral graft rejection in patients undergoing ABO-incompatible kidney transplantation.

Methods

In our study, 12 patients underwent ABO-incompatible kidney transplantation. All recipients received pre-transplantation conditioning by PE or intravenous immunoglobulin (IVIG) administration. After pre-transplantation conditioning, anti-A/B antibody titers were evaluated, and transplantation was performed when the titer was below 1:8. To assess the transplantation outcome, anti-A/B antibody titers, creatinine level, estimated glomerular filtration rate (eGFR), and proteinuria levels were measured.

Results

Anti-A/B antibody titers were below 1:8 in all patients at the time of transplantation. eGFR measured on post-transplant day 14 showed that 10 patients had immediate recovery of graft function, while 2 patients had slow recovery of graft function. Short-term outcomes of ABO-incompatible kidney transplantation (measured as creatinine levels) after reducing anti-A/B antibody titers were similar to those of ABO-compatible kidney transplantation. After transplantation, the anti-A/B antibody titers were below 1:8 in 7 patients, but the remaining 5 patients required post-transplantation PE and IVIG treatment to prevent antigen-antibody reactions.

Conclusions

With the increasing demand for kidney donations, interest in overcoming the ABO incompatibility barrier has increased. PE may be an important breakthrough in increasing the availability of kidneys for transplantation.

Pros and cons for C4d as a biomarker

The introduction of C4d in daily clinical practice in the late nineties aroused an ever-increasing interest in the role of antibody-mediated mechanisms in allograft rejection. As a marker of classical complement activation, C4d made it possible to visualize the direct link between anti-donor antibodies and tissue injury at sites of antibody binding in a graft. With the expanding use of C4d worldwide several limitations of C4d were identified. For instance, in ABO-incompatible transplantations C4d is present in the majority of grafts but this seems to point at 'graft accommodation' rather than antibody-mediated rejection. C4d is now increasingly recognized as a potential biomarker in other fields where antibodies can cause tissue damage, such as systemic autoimmune diseases and pregnancy. In all these fields, C4d holds promise to detect patients at risk for the consequences of antibody-mediated disease. Moreover, the emergence of new therapeutics that block complement activation makes C4d a marker with potential to identify patients who may possibly benefit from these drugs. This review provides an overview of the past, present, and future perspectives of C4d as a biomarker, focusing on its use in solid organ transplantation and discussing its possible new roles in autoimmunity and pregnancy.

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.

Terminal complement inhibition decreases antibody-mediated rejection in sensitized renal transplant recipients

Sensitized renal transplant recipients with high levels of donor-specific alloantibody (DSA) commonly develop antibody-mediated rejection (AMR), which may cause acute graft loss or shorten allograft survival. We examined the efficacy of terminal complement inhibition with the humanized anti-C5 antibody, eculizumab, in the prevention AMR in renal transplant recipients with a positive crossmatch against their living donor. The incidence of biopsy-proven AMR in the first 3 months posttransplant in 26 highly sensitized recipients of living donor renal transplants who received eculizumab posttransplant was compared to a historical control group of 51 sensitized patients treated with a similar plasma exchange (PE)-based protocol without eculizumab. The incidence of AMR was 7.7% (2/26) in the eculizumab group compared to 41.2% (21/51) in the control group (p = 0.0031). Eculizumab also decreased AMR in patients who developed high levels of DSA early after transplantation that caused proximal complement activation. With eculizumab, AMR episodes were easily treated with PE reducing the need for splenectomy. On 1-year protocol biopsy, transplant glomerulopathy was found to be present in 6.7% (1/15) eculizumab-treated recipients and in 35.7% (15/42) of control patients (p = 0.044). Inhibition of terminal complement activation with eculizumab decreases the incidence of early AMR in sensitized renal transplant recipients (ClincalTrials.gov number NCT006707).

Desensitization protocols and their outcome

In the last decade, transplantation across previously incompatible barriers has increasingly become popular because of organ donor shortage, availability of better methods of detecting and characterizing anti-HLA antibodies, ease of diagnosis, better understanding of antibody-mediated rejection, and the availability of effective regimens. This review summarizes all manuscripts published since the first publication in 2000 on desensitized patients and discusses clinical outcomes including acute and chronic antibody-mediated rejection rate, the new agents available, kidney paired exchange programs, and the future directions in sensitized patients. There were 21 studies published between 2000 and 2010, involving 725 patients with donor-specific anti-HLA antibodies (DSAs) who underwent kidney transplantation with different desensitization protocols. All studies were single center and retrospective. The patient and graft survival were 95% and 86%, respectively, at a 2-year median follow-up. Despite acceptable short-term patient and graft survivals, acute rejection rate was 36% and acute antibody-mediated rejection rate was 28%, which is significantly higher than in nonsensitized patients. Recent studies with longer follow-up of those patients raised concerns about long-term success of desensitization protocols. The studies utilizing protocol biopsies in desensitized patients also reported higher subclinical and chronic antibody-mediated rejection. An association between the strength of DSAs determined by median fluorescence intensity values of Luminex single-antigen beads and risk of rejection was observed. Two new agents, bortezomib, a proteasome inhibitor, and eculizumab, an anti-complement C5 antibody, were recently introduced to desensitization protocols. An alternative intervention is kidney paired exchange, which should be considered first for sensitized patients.

Findings of graft biopsy specimens within 90 days after ABO blood group incompatible living donor kidney transplantation compared with ABO-identical and non-identical transplantation

As immunosuppressive therapy has advanced, we have markedly improved the outcome of ABO blood group incompatible living donor kidney transplantation. Consequently, graft survival at early phase after ABO-incompatible transplantation has been favorable than ABO-compatible transplantation in Japan. But in these days, it has been assumed that transplant glomerulopathy within one yr after ABO-incompatible kidney transplantation might be significantly precipitated. That may be because of chronic, active antibody-mediated rejection (AMR). We performed kidney graft biopsies at the early phase within 90 d after living donor kidney transplantation that involved the episode and protocol biopsies and studied findings of graft biopsy specimens when compared with ABO incompatible and compatible involving non-identical and identical transplantations. In ABO-incompatible transplant cases, the ratio occurring glomerulitis, especially severe injury of g 2-3, was significantly higher than that of identical and non-identical transplant cases (p < 0.01). There was no significant difference in t score, i score, ptc score and v score between three transplant groups. The cases occurring AMR were concordant with the cases recognized with severe glomerulitis. AMR was difficult to be diagnosed by C4d analysis in ABO-incompatible transplant cases. Glomerular injury score, g score, may be considered as more significant and the injury should be cured thoroughly.

Significance and implications of capillaritis during acute rejection of kidney allografts

BACKGROUND.: Anti-human leukocyte antigen antibodies (a-HLA) cause graft injury identified by C4d in peritubular capillaries. We investigated whether a-HLA relate to episodes of C4d negative acute rejection (AR). METHODS.: We analyzed 878 kidney recipients transplanted from January 2000 to December 2006. Pretransplant, 36% of these crossmatch negative recipients had a-HLA measured by solid phase assays. RESULTS.: AR occurred in 154 patients (18%) and 11 of them (9.4%) were C4d+. Forty-six percent of ARs were diagnosed by protocol biopsy. The risk of C4d-AR was increased in patients with a-HLA class I with donor specificity (DSA-I) (hazard ratio=1.519; confidence interval, 1.02-2.26; P=0.039). DSA-II were not associated with an increased risk of C4d-AR. The relationship between DSA-I and C4d-AR was independent of recipient age, BK nephropathy, and HLA mismatches. Compared with DSA-, in DSA+ recipients C4d-AR were most often histologically "borderline." DSA+ was associated with capillaritis in the biopsy (glomerulitis, 6.1% vs. 32%, P=0.003; peritubular capillaritis: 13% vs. 40%, P=0.0009). Compared with no AR, C4d-AR with capillaritis was associated with reduced graft survival (hazard ratio=4.164; confidence interval, 1.763-9.832; P=0.001), independent of other variables. This association was observed even in the cases of borderline AR. CONCLUSIONS.: DSA-I increases the risk of C4d-AR. The presence of DSA-I or II is associated with capillaritis during AR. Capillaritis is associated with reduced graft survival.

Blood group O recipients associated with early graft deterioration in living ABO-incompatible kidney transplantation

BACKGROUND

Blood group O individuals are known to have larger amounts of anti-ABO blood group (anti-A/B) IgG antibodies than A or B individuals. Therefore, in ABO-incompatible (ABOI) kidney transplantation (KTX), it is expected that blood group O recipients are more likely to suffer graft damage, because anti-A/B IgG antibodies are believed to be responsible for worse graft outcomes.

METHODS

This study assessed the graft outcomes between blood group O and non-O recipients in ABOI-KTX. A total of 164 consecutive recipients who underwent ABOI-KTX between 1990 and 2007 under three different immunosuppressive protocols were enrolled in this study. The study population was divided into two groups: (i) recipients with blood group O (n=87) and (ii) recipients with blood group A or B (non-O) (n=77).

RESULTS

High anti-A/B IgG titers were predominant in the O group (P<0.001), whereas no significant difference was observed in the IgM titers. The overall graft survival rate did not differ between the two groups; however, the 6-month graft survival rate was significantly lower in the O group (86% vs. 97%, P=0.011). Among 14 recipients who suffered graft loss within 6 months after transplantation, 12 (86%) were O recipients. The cumulative incidence of acute antibody-mediated rejection was significantly higher in the O group (60 days, 31 vs. 14%, P=0.013).

CONCLUSION

Our results may indicate that being a blood group O recipient is at great risk for experiencing early allograft deterioration, probably caused by anti-A/B IgG antibodies in ABOI-KTX.

Combination of peritubular c4d and transplant glomerulopathy predicts late renal allograft failure

The histologic associations and clinical implications of peritubular capillary C4d staining from long-term renal allografts are unknown. We identified 99 renal transplant patients who underwent an allograft biopsy for renal dysfunction at least 10 yr after transplantation, 25 of whom were C4d-positive and 74 of whom were C4d-negative. The average time of the index biopsy from transplantation was 14 yr in both groups. Compared with C4d-negative patients, C4d-positive patients were younger at transplantation (29 +/- 13 versus 38 +/- 12 yr; P < 0.05) and were more likely to have received an allograft from a living donor (65 versus 35%; P < 0.001). C4d-positive patients had more inflammation, were more likely to have transplant glomerulopathy, and had worse graft outcome. The combined presence of C4d positivity, transplant glomerulopathy, and serum creatinine of >2.3 mg/dl at biopsy were very strong predictors of rapid graft loss. C4d alone did not independently predict graft loss. Retrospective staining of historical samples from C4d-positive patients demonstrated C4d deposition in the majority of cases. In summary, these data show that in long-term renal allografts, peritubular capillary staining for C4d occurs in approximately 25% of biopsies, can persist for many years after transplantation, and strongly predicts graft loss when combined with transplant glomerulopathy.

Acute antibody-mediated rejection in living ABO-incompatible kidney transplantation: long-term impact and risk factors

The impact of acute antibody-mediated rejection (AAMR) on the long-term outcome on ABO-incompatible (ABOI) kidney transplantation is not well understood. We retrospectively analyzed the long-term impact of AAMR and risk factors for AAMR in 57 consecutive recipients performed between 1999 and 2004. Nineteen patients (33%) who developed AAMR within 3 months posttransplantation constituted of the AMR group. The graft survival rate was significantly lower in the AMR group (AMR vs. non-AMR, respectively; 5 years: 84% vs. 95%; 8 years: 45% vs. 95%; p = 0.009). The prevalence of transplant glomerulopathy at 1 year posttransplantation was significantly higher in the AMR group (AMR 64% vs. non-AMR 3%, p < 0.001). Multivariate analysis demonstrated that anti-blood group IgG antibody titers of 1:32 at the time of transplantation (OR, 9.52; p = 0.041) and donor-specific anti-HLA antibodies (DSHA) detected by Luminex single bead method (OR, 5.68; p = 0.015) were independent risk factors for AAMR regardless of baseline anti-blood group IgG antibody titers. Our results indicate that AAMR has a heavy impact on the long-term outcome and preoperative DSHA appears to have a more significant association with poor graft outcomes than anti-blood group antibodies, even in ABOI kidney transplantation.

C4d deposition without rejection correlates with reduced early scarring in ABO-incompatible renal allografts

C4d deposition in peritubular capillaries is a specific marker for the presence of antidonor antibodies in renal transplant recipients and is usually associated with antibody-mediated rejection (AMR) in conventional allografts. In ABO-incompatible grafts, however, peritubular capillary C4d is often present on protocol biopsies lacking histologic features of AMR; the significance of C4d in this setting remains unclear. For addressing this, data from 33 patients who received ABO-incompatible renal allografts (after desensitization) were retrospectively reviewed. Protocol biopsies were performed at 1 and/or 3 and 6 mo after transplantation in each recipient and at 12 mo in 28 recipients. Twenty-one patients (group A) had strong, diffuse peritubular capillary C4d staining without histologic evidence of AMR or cellular rejection on their initial protocol biopsies. The remaining 12 patients (group B) had negative or weak, focal peritubular capillary C4d staining. Three grafts (two in group B) were lost but not as a result of AMR. Excluding these three patients, serum creatinine levels were similar in the two groups at 6 and 12 mo after transplantation and at last follow-up; however, recipients in group A developed significantly fewer overall chronic changes, as scored by the sum of Banff chronic indices, than group B during the first year after transplantation. These results suggest that diffuse peritubular capillary C4d deposition without rejection is associated with a lower risk for scarring in ABO-incompatible renal allografts; the generalizability of these results to conventional allografts remains unknown.

ABO-incompatible kidney transplantation using antigen-specific immunoadsorption and rituximab: a 3-year follow-up

BACKGROUND

In 2001 a protocol for ABO-incompatible (ABOi) kidney transplantation based on antigen-specific immunoadsorption and rituximab was introduced at our center, short-term results being comparable with those of ABO-compatible (ABOc) living donor kidney transplantation. Of greater importance, however, is long-term graft function, thus far not evaluated. The aim of this study was therefore to assess long-term results of this protocol.

METHODS

Twenty ABOi kidney recipients with more than 12-month follow-up were included in the study: all adult crossmatch negative ABOi kidney recipients (n=15) were compared with an adult ABOc living donor recipient control group (n=30), and all pediatric ABOi kidney recipients (<16 years of age) (n=5) were compared with a group of pediatric ABOc kidney recipients (n=18).

RESULTS

Mean follow-up was three years. There was no significant difference in patient survival, nor in graft survival or in the incidence of acute rejection in any of the groups. In the adult kidney recipients mean glomerular filtration rate was equivalent at all time points (79-83 mL/min), as was Deltas-creatinine. In the pediatric groups, Deltas-creatinine was similar but glomerular filtration rate lower among the ABOi kidney recipients. There was a significant reduction (P<0.0001) without rebound in A/B antibody titers after transplantation (median IgG 1:2 and median IgM 1:1>1 year posttransplant) compared with pretransplant levels (median IgG 1:32 and IgM 1:16).

CONCLUSION

We conclude that ABOi kidney transplantation using antigen-specific immunoadsorption and rituximab is equivalent to ABOc living donor kidney transplantation. ABOi transplantation after this protocol does not have a negative impact on long-term graft function.

Banff 07 classification of renal allograft pathology: updates and future directions

The 9th Banff Conference on Allograft Pathology was held in La Coruna, Spain on June 23-29, 2007. A total of 235 pathologists, clinicians and scientists met to address unsolved issues in transplantation and adapt the Banff schema for renal allograft rejection in response to emerging data and technologies. The outcome of the consensus discussions on renal pathology is provided in this article. Major updates from the 2007 Banff Conference were: inclusion of peritubular capillaritis grading, C4d scoring, interpretation of C4d deposition without morphological evidence of active rejection, application of the Banff criteria to zero-time and protocol biopsies and introduction of a new scoring for total interstitial inflammation (ti-score). In addition, emerging research data led to the establishment of collaborative working groups addressing issues like isolated 'v' lesion and incorporation of omics-technologies, paving the way for future combination of graft biopsy and molecular parameters within the Banff process.

ABO incompatible kidney transplantation

PURPOSE OF REVIEW

Although ABO incompatible kidney transplantation is increasingly recognized as effective, the procedure is still evolving. The purpose of this review is to summarize recent advances in this area.

RECENT FINDINGS

Short to intermediate-term outcome appears good, although long-term results are still preliminary. Pretransplant risk stratification based on antidonor antibody titer may be of limited value. Splenectomy, previously reported to be an important component of ABO incompatible transplantation, appears to be avoidable under many circumstances. The wider implementation of A2 blood group incompatible transplantation shortens waiting time for deceased donor transplantation of blood group B recipients without significantly disadvantaging others. The diagnosis of acute humoral rejection has become clearer following the recognition that C4d deposition commonly occurs in well functioning ABO incompatible allografts. The long-term implications of acute humoral rejection appear substantial even following successful acute therapy, with a significant percentage of patients developing chronic humoral rejection manifested as transplant glomerulopathy. Finally, although ABO incompatible transplantation entails increased expense, when compared with maintenance dialysis and taking into account the health related quality of life benefits of a successful transplant, it is clearly cost effective.

SUMMARY

ABO incompatible kidney transplantation is an effective therapy, and will become more widely implemented in the future.

Antibody-Mediated Rejection

The introduction of both complement 4d (C4d) staining in renal allograft biopsies and sensitive methods to detect anti-human leukocyte antigen antibodies, such as single antigen bead flow assays, into tissue-typing techniques have shown the importance of antibody-mediated alloimmune response in kidney transplantation. The use of these sensitive methods, combined with the increased number of transplants in highly sensitized patients with donor-specific antibodies, or patients receiving desensitization protocols, have increased the awareness and thus the incidence of acute antibody-mediated rejection. Chronic rejection also can be mediated through alloantibodies, and the term chronic antibody-mediated rejection recently was proposed. In this review article we summarize the current knowledge of the role of alloantibodies in transplantation, the diagnosis and treatment of acute and chronic antibody-mediated rejection, and their effect on graft function and outcome.

Polyomavirus-associated nephropathy risk in kidney transplants: the influence of recipient age and donor gender

Polyomavirus-associated nephropathy (PVAN) is a frequent cause of kidney transplant failure. We determined the risk factors for biopsy-proven PVAN among 1027 recent kidney transplant recipients by univariate and multivariate analyses. The rate of PVAN was determined over an univariate and multivariate analysis over an average of 30 months of follow-up of patients receiving predominantly living donor grafts with antibody induction and sequential surveillance biopsies to detect subclinical graft disease. Seventy-four transplant recipients were diagnosed with PVAN with the finding made on surveillance biopsy in 40 patients. These 40 cases did not differ from the 34 non-surveillance cases with respect to baseline clinical characteristics or initial histological features. Older recipient age and female donor gender were independent risks associated with PVAN. Factors not linked to PVAN risk included the use and type of induction agent, use of tacrolimus vs sirolimus, the number of human lympocyte antigen (HLA) mismatches, or the frequency of acute rejection. We conclude that PVAN preferentially affects older age patients and allografts from female donors but is unrelated to immunological risk, choice of immunosuppression, or rejection history.

Subclinical acute antibody-mediated rejection in positive crossmatch renal allografts

Subclinical antibody-mediated rejection (AMR) has been described in renal allograft recipients with stable serum creatinine (SCr), however whether this leads to development of chronic allograft nephropathy (CAN) remains unknown. We retrospectively reviewed data from 83 patients who received HLA-incompatible renal allografts following desensitization to remove donor-specific antibodies (DSA). Ten patients had an allograft biopsy showing subclinical AMR [stable SCr, neutrophil margination in peritubular capillaries (PTC), diffuse PTC C4d, positive DSA] during the first year post-transplantation; 3 patients were treated with plasmapheresis and intravenous immunoglobulin. Three patients had a subsequent rise in SCr and an associated biopsy with AMR; 5 others showed diagnostic or possible subclinical AMR on a later protocol biopsy. One graft was lost, while remaining patients have normal or mildly elevated SCr 8-45 months post-transplantation. However, the mean increase in CAN score (cg + ci + ct + cv) from those biopsies showing subclinical AMR to follow-up biopsies 335 +/- 248 (SD) days later was significantly greater (3.5 +/- 2.5 versus 1.0 +/- 2.0, p = 0.01) than that in 24 recipients of HLA-incompatible grafts with no AMR over a similar interval (360 +/- 117 days), suggesting that subclinical AMR may contribute to development of CAN.

A newly recognized blood group in domestic shorthair cats: the Mik red cell antigen

BACKGROUND

Naturally occurring alloantibodies produced against A and B red cell antigens in cats can cause acute hemolytic transfusion reactions. Blood incompatibilities, unrelated to the AB blood group system, have also been suspected after blood transfusions through routine crossmatch testing or as a result of hemolytic transfusion reactions.

HYPOTHESIS

Incompatible crossmatch results among AB compatible cats signify the presence of a naturally occurring alloantibody against a newly identified blood antigen in a group of previously never transfused blood donor cats. The associated alloantibody is clinically important based upon a hemolytic transfusion reaction after inadvertent transfusion of red cells expressing this red cell antigen in a feline renal transplant recipient that lacks this red cell antigen.

METHODS

Blood donor and nonblood donor cats were evaluated for the presence of auto- and alloantibodies using direct antiglobulin and crossmatch tests, respectively, and were blood typed for AB blood group status. Both standard tube and novel gel column techniques were used.

RESULTS

Plasma from 3 of 65 cats and 1 feline renal transplant recipient caused incompatible crossmatch test results with AB compatible erythrocytes indicating these cats formed an alloantibody against a red cell antigen they lack, termed Mik. The 3 donors and the renal transplant recipient were crossmatch-compatible with one another. Tube and gel column crossmatch test results were similar.

CONCLUSIONS AND CLINICAL IMPORTANCE

The absence of this novel Mik red cell antigen can be associated with naturally occurring anti-Mik alloantibodies and can elicit an acute hemolytic transfusion reaction after an AB-matched blood transfusion.

The interleukin-12 family: new players in transplantation immunity?

Since several years ago, interleukin (IL)-12 is known to be responsible for the differentiation of naive CD4+ T cells into type 1 helper T cells producing interferon-gamma. Recently, two other cytokines of the IL-12 family, IL-23 and IL-27, were shown to play key roles in experimental autoimmune disorders mediated by Th17 cells, a novel pro-inflammatory CD4+ T-cell subset secreting IL-17. As our knowledge of IL-12 family members is rapidly growing and changing, it will be important to specify their involvement in the induction and regulation of allograft rejection in animal models as well as in clinical settings. Herein, we review key features of cytokines belonging to the IL-12 family and discuss their potential relevance to transplantation immunity.

Isolated donor specific alloantibody-mediated rejection after ABO compatible liver transplantation

Antibody-mediated rejection (AMR) after liver transplantation is recognized in ABO incompatible and xeno-transplantation, but its role after ABO compatible liver transplantation is controversial. We report a case of ABO compatible liver transplantation that demonstrated clinical, serological and histological signs of AMR without evidence of concurrent acute cellular rejection. AMR with persistently high titers of circulating donor specific antibodies resulted in graft injury with initial centrilobular hepatocyte necrosis, fibroedematous portal expansion mimicking biliary tract outflow obstruction, ultimately resulting in extensive bridging fibrosis. Immunofluorescence microscopy demonstrated persistent, diffuse linear C4d deposits along sinusoids and central veins. Despite intense therapeutic intervention including plasmapheresis, IVIG and rituximab, AMR led to graft failure. We present evidence that an antibody-mediated alloresponse to an ABO compatible liver graft can cause significant graft injury independent of acute cellular rejection. AMR shows distinct histologic changes including a characteristic staining profile for C4d.

Complications, resource utilization, and cost of ABO-incompatible living donor kidney transplantation

BACKGROUND

The transplantation of living donor renal allografts across blood group barriers requires protocols to reduce and maintain anti-blood group antibody at safe levels. These protocols lead to an increase in resource utilization and cost of transplantation and may result in increased complications.

METHODS

In this retrospective study, we compared 40 ABO-incompatible to 77 matching ABO-compatible living donor renal allografts with respect to complications, resource utilization, and cost from day -14 to 90 days after transplantation.

RESULTS

Overall, surgery-related complications and resource utilization were increased in the ABO-incompatible group, primarily due to the desensitization protocol and antibody-mediated rejection. In the absence of rejection, the mean number of complications was similar for both groups. ABO-incompatible kidney transplantation was approximately 38,000 US dollars more expensive than ABO-compatible transplants, but was cost effective when compared to maintaining the patient on dialysis while waiting for a blood group compatible deceased donor kidney. Actuarial graft and patient survival was similar in the two groups.

CONCLUSIONS

We conclude that ABO-incompatible living donor kidney transplantation is a viable option for patients whose only donor is blood group incompatible despite the additional resource utilization and cost of therapy.