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

Success rate and safety of living donor kidney transplantation in ABO blood group incompatible relatives: A systematic review and meta-analysis

BACKGROUND

Kidney transplantation is considered an ideal treatment for end-stage renal disease (ESRD) because it provides a longer and better quality of life than dialysis. ABO-incompatible (ABO-I) kidney transplantation relies on two principles: (i) removal of antibodies from a blood group; and (ii) inhibition of reappearance of blood group antibodies by intensifying the induction and maintenance of immunosuppression. This systematic review aimed to analyze the success and safety of ABO-I live-donor kidney transplantation.

METHODS

Databases, including Google Scholar, PubMed, Embase, Web of Science, and Medline were searched. Search duration was from the database establishment to December 2022. A thorough search was performed for relevant studies investigating the success and safety of ABO-I live-donor kidney transplantation. Two investigators independently extracted literature information and assessed the quality of the included studies. Heterogeneity test was performed using Cochrane's Q and chi-squared tests. All statistical analyses were performed using R software (version 4.2.1).

RESULTS

The search for relevant literature in the five electronic databases yielded 1238 articles. Of the 1238 articles, only 15 were included. Meta-analysis of outcomes from five studies showed a survival rate of 0.93 (95% confidence interval [CI]: 0.88 to 0.97, P < 0.001) after ≥3 years, while outcomes from 12 studies revealed a short-term patient survival rate of 0.94 (95% CI: 0.92 to 0.96, P = 0.75). In contrast, long- and short-term graft survival rates were 0.89 (95% CI: 0.75 to 0.96, P < 0.001) and 0.94 (95% CI: 0.90 to 0.97, P < 0.001), respectively. Incidence rates of infectious, surgical, and medical complications were 0.31 (95% CI: 0.22 to 0.41, P < 0.001), 0.12 (95% CI: 0.05 to 0.25, P < 0.001), and 0.38 (95% CI: 0.17 to 0.66, P < 0.001), respectively.

CONCLUSION

Good long- and short-term patient outcomes and graft survival rates were observed after ABO-I kidney transplantation. Similarly, the safety of performing kidney transplantations from living donors with ABO-I blood groups was established by the results of the current meta-analysis. Therefore, ABO-I live-donor kidney transplantations should be encouraged to reduce the time recipients spend on waiting lists and supplement the existing paired-exchange donor program.

Hyperacute rejection in ABO-incompatible kidney transplantation: Significance of isoagglutinin subclass

INTRODUCTION

ABO-incompatible transplantation has expanded the limited donor pool for kidney transplantation. Despite the successful desensitization protocols and immunosuppression, undesirable cases of hyperacute rejection occurs.

OBJECTIVE

Flow cytometry was used to measure isoagglutinin titer and its IgG subclasses in assessment of the cause of hyperacute rejection in ABO-incompatible kidney transplantation.

MATERIALS AND METHODS

The recipient was admitted for kidney transplantation due to end-stage renal disease. Pre-transplantation work-up for ABO-incompatible kidney transplantation included blood group typing, HLA DNA typing and HLA antibody analyses. HLA crossmatch analysis was conducted using donor lymphocytes and anti-HLA antibody assay using Luminex panel reactive antibody test (One Lambda, Inc., Canoga Park, CA). Desensitization protocol was composed of therapeutic plasma exchange sessions and rituximab.

RESULTS

Despite negative HLA crossmatch results, a case of hyperacute rejection occurred after living donor kidney transplantation. Rejection resulted in immediate removal of graft, and the patient later received a second kidney transplantation. Retrospective evaluation of isoagglutinin titer and its subclasses using flow cytometry identified the cause of rejection to increased IgG1 subclass. Desensitization protocol for ABO-incompatible kidney transplantation now implements further caution for blood group O recipients.

DISCUSSION

Hyperacute rejection resulting from increased IgG1 isoagglutinin subclass has not been previously confirmed using flow cytometry. Unfortunate outcome of this rejection case provides insight to how we should approach and ensure successful ABO-incompatible kidney transplantation.

ABO-incompatible kidney transplantation in perspective of deceased donor transplantation and induction strategies: a propensity-matched analysis

Kidney transplant candidates are blood group incompatible with roughly one out of three potential living donors. We compared outcomes after ABO‐incompatible (ABOi) kidney transplantation with matched ABO‐compatible (ABOc) living and deceased donor transplantation and analyzed different induction regimens. We performed a retrospective study with propensity matching and compared patient and death‐censored graft survival after ABOi versus ABOc living donor and deceased donor kidney transplantation in a nationwide registry from 2006 till 2019. 296 ABOi were compared with 1184 center and propensity‐matched ABOc living donor and 1184 deceased donor recipients (matching: recipient age, sex, blood group, and PRA). Patient survival was better compared with deceased donor [hazard ratio (HR) for death of HR 0.69 (0.49–0.96)] and non‐significantly different from ABOc living donor recipients [HR 1.28 (0.90–1.81)]. Rate of graft failure was higher compared with ABOc living donor transplantation [HR 2.63 (1.72–4.01)]. Rejection occurred in 47% of 140 rituximab versus 22% of 50 rituximab/basiliximab, and 4% of 92 alemtuzumab‐treated recipients (P < 0.001). ABOi kidney transplantation is superior to deceased donor transplantation. Rejection rate and graft failure are higher compared with matched ABOc living donor transplantation, underscoring the need for further studies into risk stratification and induction therapy [NTR7587, www.trialregister.nl].

ABO incompatibility in renal transplantation

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

Immunoglobulin isotype compositions of ABO specific antibodies are dependent on the individual patient blood group and blood group specificity: Results from a healthy donor cohort

Antibodies specific for the blood group ABO system antigens are of clinical significance and immunological interest. Routine clinical methods typically employ direct or indirect haemagglutination methods to measure IgM and IgG, respectively. We have developed a simple, single tube method to quantify IgM, IgG, and IgA specific for A and B antigens in order to improve accuracy and reproducibility, and to investigate the relationships between ABO group antibody type, and antibody level. Plasma samples from 300 healthy blood donors were studied. Levels of IgM and IgG binding to reagent group A and B red cells were measure by agglutination (HA) and multi-colour flow cytometry (MC-FC). IgA was also measured by MC-FC. Our FC method was found to be significantly more reproducible than HA for the measurement of blood group A and B specific antibodies. We found statistically significant correlations between antibodies measured by GC-HA and MC-FC, but sufficient differences to indicate that these methods are not equivalent. By MC-FC, IgM, IgG and IgA levels and isotope profiles were found to be dependent on both the donor ABO type and the specificity of the antibody. This study demonstrated heterogeneity in the immunoglobulin class profiles of ABO-blood group specific antibodies within the healthy population. Differences in isotype profiles of ABO-blood group specific antibodies may indicate fundamental differences in the immune mechanisms that generate these antibodies. This is likely to be relevant to the clinical situations where management or diagnosis depend on ABO-specific antibody detection and measurement.

Use of immunoadsorption columns in ABO-incompatible renal transplantation: A prospective study at a tertiary care center in India

Background

We present our experience of ABO-incompatible renal transplant using immunoadsorption (IA) columns. We have compared efficacy of two commercially available columns.

Methods

This single-center prospective study was conducted at Army Hospital Research and Referral, Delhi. All consecutive ABO-incompatible renal transplants from January 2014 to February 2018 were analyzed. Of 30 patients who underwent transplantations, 28 underwent antibody depletion with immunoadsorption columns. Of them, 14 cases were in the "Glycosorb group," while 14 in the "Adsopak group."

Results

The donors in the Adsopak group were older than those in the Glycosorb group (p < 0.05). Both groups had spousal donors in majority. The cutoff for the antibody titer was 1:8. The median titer in the Adsopak group was 128 (range, 1:4 to 1:2048), while that in the Glycosorb group was 24 (range, 1:8 to 1:128). All patients in the Glycosorb group had baseline titers ≤1:128, while 13 patients in the Adsopak group had baseline titers ≤1:512. Nil titer was achievable with Glycosorb® (50%,7/14) but not with Adsopak® (P < 0.01). Around 4 sessions were required for the Glycosorb group, while around 8 sessions were required for the Adsopak group before transplantation (p < 0.001). The Glycosorb group was advantageous in terms of graft failure because no rejection was noticed in these patients in their follow-up period. Three patients in the Adsopak group developed rejection (two had mixed rejection, and one had antibody-mediated rejection). Four patients died of sepsis (three in the Glycosorb and one in the Adsopak group). Lower baseline serum creatinine level was achieved in the Glycosorb group.

Conclusions

Results of ABO-incompatible renal transplantation were satisfactory, and the use of immunoadsorption columns could effectively deplete antibody titers. Glycosorb columns were more efficient than Adsopak columns. Graft survival was better with Glycosorb. Posttransplant infections were a major cause of mortality.

Current protocols and outcomes of ABO-incompatible kidney transplantation

One of the principal obstacles in transplantation from living donors is that approximately 30% are immunologically incompatible because of the presence in the recipient of antibodies directed against the human leukocyte antigen system of the donor or because of the incompatibility of the ABO system. The aim of this review is to describe the more recent data from the literature on the different protocols used and the clinical outcomes of ABO-incompatible kidney transplantation. Two different strategies are used to overcome these barriers: desensitization of the recipient to remove the antibodies and to prevent their rebound after transplantation and the exchange of organs between two or more pairs. The largest part of this review is dedicated to describing the techniques of desensitization. Even if the first reports of successful renal transplantation between ABO-incompatible pairs have been published by 1980, the number of ABO-incompatible transplants increased substantially in this century because of our improved knowledge of the immune system and the availability of new drugs. Rituximab has substantially replaced splenectomy. The technique of apheresis has improved and more recently a tailored desensitization proved to be the more efficient strategy avoiding an excess of immunosuppression with the related side effects. Recent reports document outcomes for such transplantation similar to the outcomes of standard transplantation.

Short-Term Outcomes of ABO-Incompatible Living Donor Kidney Transplantation With Uniform Protocol: Significance of Baseline Anti-ABO Titer

Antibody-mediated rejection (AMR) is one of the major causes of poor outcomes in ABO-incompatible kidney transplantation (ABOi KT). Studies investigating AMR risk factors found that anti-ABO titer is a major issue. However, the significance of antibody titer has been debated. This retrospective study analyzed AMR risk factors in 59 patients who underwent ABOi KT between August 2010 and January 2015. We also analyzed AMR risk factors in recipients with high anti-ABO baseline titers (≥1:64 on dithiothreitol at 37°C phase or ≥1:256 on antihuman globulin phase). The 2-year patient survival rate was 95.8%, and the 2-year graft survival rate was 94.9%. Nine patients (15.3%) experienced clinical (6 of 59 [10.2%]) or subclinical (3 of 59 [5.1%]) AMR. One patient experienced graft loss from hyperacute rejection. AMR risk factor analysis revealed that baseline antibody titer was associated with incidence of AMR. In patients with high baseline titers, low doses of rituximab (200-mg single-dose), an antibody against CD20, was predictive for AMR. Six patients who received pretransplant intravenous immunoglobulin did not experience AMR even when they had high baseline antibody titers. Our results indicate that a high baseline antibody titer affected the incidence of AMR. ABOi KT candidates with high baseline titers need to undergo an intensified preconditioning protocol, including high-dose rituximab (375 mg/m(2)) and intravenous immunoglobulin.

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

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

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

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

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

Strategies to overcome the ABO barrier in kidney transplantation

Kidney transplantation across the ABO blood group barrier was long considered a contraindication for transplantation, but in an effort to increase donor pools, specific regimens for ABO-incompatible (ABOi) transplantation have been developed. These regimens are now widely used as an integral part of the available treatment options. Various desensitization protocols, commonly based on transient depletion of preformed anti-A and/or anti-B antibodies and modulation of B-cell immunity, enable excellent transplant outcomes, even in the long-term. Nevertheless, the molecular mechanisms behind transplant acceptance facilitated by a short course of anti-humoral treatment are still incompletely understood. With the evolution of efficient clinical programmes, tailoring of recipient preconditioning based on individual donor-recipient blood type combinations and the levels of pretransplant anti-A/B antibodies has become possible. In the context of low antibody titres and/or donor A2 phenotype, immunomodulation and/or apheresis might be dispensable. A concern still exists, however, that ABOi kidney transplantation is associated with an increased risk of surgical and infectious complications, partly owing to the effects of extracorporeal treatment and intensified immunosuppression. Nevertheless, a continuous improvement in desensitization strategies, with the aim of minimizing the immunosuppressive burden, might pave the way to clinical outcomes that are comparable to those achieved in ABO-compatible transplantation.

Determination of specimen storage conditions for measuring isoagglutinin titers

BACKGROUND

This study aimed to determine the optimal specimen storage conditions for isoagglutinin titration by changing storage time and temperature.

STUDY DESIGN AND METHODS

Serum specimens from 60 individuals were stored at room temperature (RT, 25 °C) or at 4 °C and tested every 24 hours until 96 hours by the immediate spin (IS) method and the anti-human globulin method using dithiothreitol (DTT-AHG). These titer results were compared with the titers which were measured when the samples arrived. The titer endpoint was defined as the highest dilution, with clinically meaningful differences defined as more than 4-fold differences (two serial dilutions) in titer.

RESULTS

Of the specimens stored at RT for 24, 48, 72, and 96 hours, 5%, 12%, 12%, and 12%, respectively, showed two-fold (one dilution) differences by the IS method, and 8%, 8%, 8%, and 10%, respectively, showed two-fold (one dilution) differences with the DTT-AHG method. Of the specimens refrigerated for 24, 48, 72, and 96 hours, 8%, 10%, 13%, and 13%, respectively, showed two-fold (one dilution differences) by the IS method, and 13%, 12%, 12%, and 12%, respectively, showed two-fold (one dilution) differences with the DTT-AHG method.

CONCLUSIONS

Specimens stored for up to 96 hours at RT and 4 °C showed similar titers using the IS and DTT-AHG methods. These findings suggest that tests can be scheduled regularly.

A systematic review of the use of rituximab for desensitization in renal transplantation

BACKGROUND

Rituximab is a B lymphocyte-depleting agent used to treat lymphoma and autoimmune diseases. Recently, it has been used for desensitization therapy in ABO-incompatible and highly sensitized recipients undergoing renal transplantation.

METHODS

A systematic review was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. Four databases and three trial registries were searched for studies comparing rituximab with non-rituximab desensitization protocols. A lack of randomized evidence precluded meta-analysis, and thus a narrative review was conducted.

RESULTS

Forty-five records met the inclusion criteria, relating to 21 individual studies (two randomized controlled trials and 19 retrospective cohort studies). Ten studies investigated the use of rituximab in ABO-incompatible patients; most found no significant differences in patient and graft outcomes when compared most frequently to splenectomy-based protocols. Nine studies of limited quality focused on highly sensitized recipients (positive cross-match, donor-specific antibody, and elevated panel reactive antibody) and demonstrated some benefits in graft survival, acute and chronic rejection, and sensitization levels with rituximab. The remaining two studies combined ABO-incompatible and highly sensitized recipients and found no statistically significant increase in infectious complications with rituximab.

CONCLUSION

Evidence of limited quality was identified to support the use of rituximab desensitization in highly sensitized recipients. Among ABO-incompatible recipients, rituximab was found to be equivalent to splenectomy, indicating that this invasive surgical procedure is not necessary. Further randomized controlled trials are required to better define the efficacy, long-term safety, and optimal dosing regimen of rituximab in this setting.

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.

ABO-incompatible kidney transplant recipients have a higher bleeding risk after antigen-specific immunoadsorption

Pretransplant removal of antiblood group ABO antibodies is the cornerstone of all current ABO-incompatible (ABOi) transplantation programmes. In our protocol, plasmapheresis (PP) is performed with a plasmafilter followed by immunoadsorption (IA) of anti-ABO antibodies. The bleeding complications of this technique are not known. We analysed the data of all 65 consecutive ABOi kidney transplantations between March 2006 and October 2013 and compared these with matched 130 ABO-compatible (ABOc) kidney transplantations. Cases differed from controls in the pre-operative regimen, which included IA-PP and rituximab, tacrolimus, mycophenolate mofetil, prednisone and immunoglobulines. Data on platelet count, blood loss and red blood cell (EC) transfusions during 48 h postoperatively were collected. ABOi patients received EC transfusions more frequently than controls (29% vs. 12%, P = 0.005). Intra-operative blood loss was higher (544 vs. 355 ml, P < 0.005) and they experienced more major bleeding (≥3 EC within 24 h, 15% vs. 2%, P < 0.0005). Platelet count decreased by 28% after the pre-operative IA. In a multivariate model, only the number of pre-operative IAs was associated with the number of ECs given (OR per IA 1.9, P < 0.05). ABOi kidney transplant recipients have a high postoperative bleeding risk, correlating with the number of pre-operative IA sessions performed.

Comparison of total and IgG ABO antibody titers in healthy individuals by using tube and column agglutination techniques

Background

Most immune reactions related to transfusion and transplantation are caused by IgM ABO antibodies. However, IgG also plays an important role in these reactions. Therefore, a method to measure antibodies, including IgG, is necessary. We investigated ABO antibody titers of healthy individuals using a column agglutination technique (CAT) with or without dithiothreitol (DTT) and compared them with titers obtained using a conventional tube method.

Methods

Among healthy adults who underwent a medical examination, 180 individuals (60 with blood group A, 60 with group B, and 60 with group O) were selected. Antibody titrations were performed using the immediate spin (IS) tube, anti-human globulin (AHG) tube, and CAT with or without DTT methods.

Results

Higher median values of anti-B and anti-A titers in groups A and B individuals, respectively, were obtained using the IS method than using the AHG method. Higher values for group O individuals were obtained using the AHG method. Higher median titers of anti-B and anti-A in group O individuals were obtained using CAT without DTT than using the AHG method. Median titers of anti-B and anti-A in all blood groups were higher in CAT without DTT than in CAT with DTT, especially for group O individuals.

Conclusions

We recommend CAT with and without DTT for titration of anti-A and anti-B, especially in group O individuals, to provide more sensitive results that include IgG data. Adjustment of insurance coverage of fees associated with antibody titration might be necessary, considering the actual cost of reagents and personnel.

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.

Do ABO blood group antigens hamper the therapeutic efficacy of mesenchymal stromal cells?

Investigation into predictors for treatment outcome is essential to improve the clinical efficacy of therapeutic multipotent mesenchymal stromal cells (MSCs). We therefore studied the possible harmful impact of immunogenic ABO blood groups antigens – genetically governed antigenic determinants – at all given steps of MSC-therapy, from cell isolation and preparation for clinical use, to final recipient outcome.

We found that clinical MSCs do not inherently express or upregulate ABO blood group antigens after inflammatory challenge or in vitro differentiation. Although antigen adsorption from standard culture supplements was minimal, MSCs adsorbed small quantities of ABO antigen from fresh human AB plasma (ABP), dependent on antigen concentration and adsorption time. Compared to cells washed in non-immunogenic human serum albumin (HSA), MSCs washed with ABP elicited stronger blood responses after exposure to blood from healthy O donors in vitro, containing high titers of ABO antibodies. Clinical evaluation of hematopoietic stem cell transplant (HSCT) recipients found only very low titers of anti-A/B agglutination in these strongly immunocompromised patients at the time of MSC treatment. Patient analysis revealed a trend for lower clinical response in blood group O recipients treated with ABP-exposed MSC products, but not with HSA-exposed products.

We conclude, that clinical grade MSCs are ABO-neutral, but the ABP used for washing and infusion of MSCs can contaminate the cells with immunogenic ABO substance and should therefore be substituted by non-immunogenic HSA, particularly when cells are given to immunocompentent individuals.

Significance of isoagglutinin titer in ABO-incompatible kidney transplantation

ABO-incompatible (ABO-i) kidney transplantation (KT) has emerged for overcoming the shortage of organ donors. Although this technique initially achieved only low graft survival due to isoagglutinin, recently developed desensitization protocols have improved survival to levels that are comparable to ABO-compatible KT. However, isoagglutinin is still regarded as a major obstacle to ABO-i KT. In this study, we evaluate the impact of isoagglutinin titer on clinical outcomes as well as factors that may influence isoagglutinin titers. In total, data from 95 patients who underwent ABO-i KT were analyzed. Preoperatively, rituximab administration and plasmapheresis were performed until the titer was reduced to ≤1:4. Retrospective analysis included blood group; timing and dosage of rituximab; isoagglutinin titer; number of plasmapheresis; and clinical outcomes including graft survival and serum creatinine. Graft survival was 95.8% (n = 91) and average serum creatinine at 1- and 1.5-year post-ABOi-KT was 1.3. Three patients died of sepsis. The identified predictors of titer-rebound after transplant were short interval (<7 days) between rituximab and first plasmapheresis (P = 0.004); high initial titer (≥256) (P = 0.023); low titer-reduction rate (P < 0.001); and blood group O (P < 0.001). One patient who experienced a rebound developed antibody-mediated rejection. With low-dose (200 mg) rituximab, the change in isoagglutinin titer-rebound was not significant and the infection rate was significantly decreased (P = 0.001). In conclusion, isoagglutinin titer-rebound within the first 2 weeks after KT may be a risk factor for rejection. The factors identified as affecting titer-rebound after KT were high initial isoagglutinin titer, low titer-reduction rate, short interval, and blood group O.

ABO-incompatible liver transplantation in acute liver failure: a single Portuguese center study

INTRODUCTION

ABO-incompatible liver transplantation (ABOi LT) is considered to be a rescue option in emergency transplantation. Herein, we have reported our experience with ABOi LT including long-term survival and major complications in these situations.

PATIENT AND METHODS

ABOi LT was performed in cases of severe hepatic failure with imminent death. The standard immunosuppression consisted of basiliximab, corticosteroids, tacrolimus, and mycophenolate mofetil. Pretransplantation patients with anti-ABO titers above 16 underwent plasmapheresis. If the titer was above 128, intravenous immunoglobulin (IVIG) was added at the end of plasmapheresis. The therapeutic approach was based on the clinical situation, hepatic function, and titer evolution. A rapid increase in titer required five consecutive plasmapheresis sessions followed by administration of IVIG, and at the end of the fifth session, rituximab.

RESULTS

From January 2009 to July 2012, 10 patients, including 4 men and 6 women of mean age 47.8 years (range, 29 to 64 years), underwent ABOi LT. At a mean follow-up of 19.6 months (range, 2 days to 39 months), 5 patients are alive including 4 with their original grafts. One patient was retransplanted at 9 months. Major complications were infections, which were responsible for 3 deaths due to multiorgan septic failure (2 during the first month); rejection episodes (4 biopsy-proven of humoral rejections in 3 patients and 1 cellular rejection) and biliary.

CONCLUSION

The use of ABOi LT as a life-saving procedure is justifiable in emergencies when no other donor is available. With careful recipient selection close monitoring of hemagglutinins and specific immunosuppression we have obtained acceptable outcomes.

Production of anti-ABO blood group antibodies after minor ABO-incompatible bone marrow transplantation in NOD/SCID/gamma(c)(null) mice

ABO incompatibility is a barrier for solid organ transplantation, but not for hematopoietic stem cell transplantation. To investigate tolerance induction, we enrolled patients who had undergone minor ABO-incompatible (O into A group, n = 6) and ABO-identical (O into O group, n = 4) bone marrow transplantation (BMT). None of the six O into A patients were positive for recipient-specific (anti-blood group A) isohemagglutinins, whereas all four O into O patients were. Peripheral blood mononuclear cells (PBMCs) were engrafted into NOD/SCID/gamma(c)(null) (NOG) mice, followed by sensitization of blood group A red blood cells. Anti-blood group A antibodies (Abs) in the sera of the patients and the human PBMC-engrafted NOG mice were measured by enzyme-linked immunosorbent assays. Anti-blood group A Abs in the patients' sera were significantly correlated with anti-A isohemagglutinin titers (p < 0.01). In the human PBMC-engrafted NOG mice, anti-blood group A Abs were significantly lower in the O into A group than in the O into O group (p < 0.05), despite ex vivo restimulation of B cells. The results of this study suggest that long after receiving minor ABO-incompatible BMT, B cells derived from newly engrafted donor precursor cells were induced tolerance to recipient-specific antigens.

Reviews on mysterious vascular endothelial cells in renal allografts

Endothelial cells (ECs) are involved in allograft rejection and are prime targets, but also key players. HLA antigens are the most prominent targets of alloantibodies in transplantation. Alloantibodies against other antigens such as ABO blood group antigens and non-HLA antigens could also be demonstrated. Alloantibodies undoubtedly cause allograft rejection. Activation of ECs by anti-EC antibodies and direct antibody- or complement mediated EC damage may be suggested. However, the mechanisms underlying acute antibody-mediated rejection (AAMR) and chronic rejection (CR) remain unclear. In this review, the relationship between vascular endothelium and rejection is discussed mainly from our reports, and the mechanism and pathogenesis of CR are discussed.

Distribution of ABO blood group antibody titers in pediatric patients awaiting renal transplantation: implications for organ allocation policy

BACKGROUND

Blood group-incompatible transplantation is one strategy used when a potential recipient does not have a compatible living donor. Current practice includes desensitization strategies to reduce antibody titers. However, when antibodies are low, in cardiac transplantation in neonates for example, no desensitization is required. This study is the first to examine the distribution of ABO blood group antibody titers in a population of pediatric patients on the deceased-donor renal transplantation waiting list.

METHODS

All patients from two pediatric nephrology centers active on the national deceased-donor waiting list had antibody titers (total immunoglobulin load) measured. A simulation modeling the effect of allocating blood group-incompatible deceased-donor kidneys to those patients with titers of 16 or lower was developed.

RESULTS

Twenty-four children were screened; eight (33.3%) had titers of either anti-A or anti-B antibodies of 8 or lower. A further three (12.5%) had either an anti-A or anti-B antibody titer of 16. Blood group A or B patients had lower antibody levels than blood group O patients. In blood group O patients, levels of anti-A antibodies were higher than anti-B antibodies (Wilcoxon signed rank test, P=0.028). The simulation model showed that a change in organ allocation policy would increase pediatric transplant activity by 2.2% and reduce the median waiting time for a transplant.

CONCLUSION

This allocation strategy may be of particular benefit to those pediatric patients who have been on the deceased-donor waiting list for a long time or those with a high calculated reaction frequency.

Case report: Eculizumab rescue of severe accelerated antibody-mediated rejection after ABO-incompatible kidney transplant

ABO-incompatible (ABOI) living donor kidney transplantation has become a well-accepted practice with standard protocols using perioperative antibody-depleting therapies to lower blood group titers to an acceptable threshold for transplantation. However, a subset of patients will experience accelerated antibody-mediated rejection (AMR) after ABOI kidney transplantation and require aggressive intervention to prevent allograft loss. Here in we report the successful use of terminal complement inhibition with eculizumab to rescue an ABOI kidney allograft with accelerated AMR refractory to salvage splenectomy and daily plasmapheresis. This case emphasizes the fact that, despite close postoperative surveillance and aggressive intervention, graft loss from accelerated AMR after ABOI kidney transplantation remains a very real risk. Eculizumab may offer a graft-saving therapeutic option for isolated cases of severe AMR after ABOI kidney transplantation refractory to standard treatment.

Outcomes of ABO-incompatible kidney transplantation in the United States

BACKGROUND

ABO incompatible (ABOi) kidney transplantation is an important modality to facilitate living donor transplant for incompatible pairs. To date, reports of the outcomes from this practice in the United States have been limited to single-center studies.

METHODS

Using the Scientific Registry of Transplant Recipients, we identified 738 patients who underwent live-donor ABOi kidney transplantation between January 1, 1995, and March 31, 2010. These were compared with matched controls that underwent ABO compatible live-donor kidney transplantation. Subgroup analyses among ABOi recipients were performed according to donor blood type, recipient blood type, and transplant center ABOi volume.

RESULTS

When compared with ABO compatible-matched controls, long-term patient survival of ABOi recipients was not significantly different between the cohorts (P=0.2). However, graft loss was significantly higher, particularly in the first 14 days posttransplant (subhazard ratio, 2.34; 95% confidence interval, 1.43-3.84; P=0.001), with little to no difference beyond day 14 (subhazard ratio, 1.28; 95% confidence interval, 0.99-1.54; P=0.058). In subgroup analyses among ABOi recipients, no differences in survival were seen by donor blood type, recipient blood type, or transplant center ABOi volume.

CONCLUSIONS

These results support the use and dissemination of ABOi transplantation when a compatible live donor is not available, but caution that the highest period of risk is immediately posttransplant.

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.

ABO blood group incompatibility: a diminishing barrier to successful kidney transplantation?

Blood type-incompatible transplantation has gained wide acceptance over the last decade. This is largely the result of B-cell-directed therapies aimed at modulating anti-blood group antibodies, which were the cause of the poor outcomes originally seen. Now rituximab (anti-CD20 and anti-B cell) has largely replaced splenectomy in preconditioning protocols, allowing for the wider implementation of ABO-incompatible transplants. Plasma exchange followed by intravenous immunoglobulin is also critical for the success of ABO-incompatible transplants. In this article, we describe the important contributions immunomodulatory drugs and antibody reduction therapies have made in achieving excellent outcomes in what was once an impenetrable barrier to transplantation.

ABO-incompatible kidney transplantation: current practice and the decade ahead

PURPOSE OF REVIEW

With rapidly growing deceased donor kidney transplant waiting lists, solutions to the shortage of kidney donors need to come from many corners. This review focuses on the current results and upcoming medications that will allow broad expansion of ABO-incompatible transplantation as one facet to combat this issue.

RECENT FINDINGS

Outcomes of ABO-incompatible kidney transplantation are comparable to standard living donor transplantation but carry a significant, early risk of antibody-mediated rejection. Reducing this early rejection risk will be critical for a broader adaption of incompatible transplants. Improvements in the measurement of isohemagglutinin antibodies with less variability, will reduce patient risk. The anti-CD20 antibody rituximab has replaced splenectomy at most centers with equivalent outcomes, eliminating the need for additional surgical intervention. Studies of complement inhibitors have proven effective in treating antibody-mediated rejection in animal models and human studies are currently ongoing. Studies in xenotransplantation show that blood group carbohydrate antigens can be effectively removed ex vivo prior to implantation. Ongoing studies of accommodation in animal models are finding protective changes in endothelial cells and the immune system that could become targets for pharmacologic manipulation.

SUMMARY

Improvements that reduce risk of early rejection and its long-term sequelae will allow ABO-incompatible kidney transplantation to be adopted broadly along with paired kidney exchange programs, to address the donor organ shortage.

Accommodation in renal transplantation: unanswered questions

PURPOSE OF REVIEW

Accommodation, an acquired resistance of an organ to immune-mediated damage, has been recognized as an outcome of renal transplantation for more than 20 years. Accommodation was originally identified in blood group-incompatible kidney transplants that survived and functioned normally in recipients with high titers of antiblood group antibodies directed against antigens in the grafts. The most compelling questions today include how often and by which mechanisms accommodation occurs, and what might be the biological implications of accommodation. This communication summarizes recent advances in addressing these questions.

RECENT FINDINGS

Because its diagnosis has depended on identification of antidonor antibodies in serum, the prevalence of accommodation has been considered low. Recent research in animal models and clinical subjects may challenge that view. This research also suggests that sublethal graft injury of various types induces accommodation and that accommodation may be a dynamic condition, eventuating into tolerance on the one hand and chronic graft injury on the other.

SUMMARY

Burgeoning lines of investigation into accommodation now portray a condition of greater prevalence than once thought, exposing pathways that may contribute to the understanding of a range of responses to transplantation.