Donor Human Leukocyte Antigen Research Articles

Should HLA and HPA-matched platelet transfusions for patients with Glanzmann Thrombasthenia or Bernard-Soulier syndrome be standardized care? A Dutch survey and recommendations.

Glanzmann thrombasthenia (GT) and Bernard-Soulier syndrome (BSS) patients require frequent platelet transfusions and hence have an increased risk for alloimmunization against donor Human Leukocyte Antigens (HLA) when no HLA-matching is performed. Knowing that Human Platelet Antigens (HPA) are located on the platelet glycoproteins that can be absent in these patients, preventive HPA-matching may also be considered. Uniform recommendations on this topic lack in transfusion guidelines making standard practice unclear, therefore, we aimed to provide a framework for matched platelet transfusions. We conducted a targeted literature search and a national survey of Dutch (pediatric) hematologists from July to September 2021. We found 20 articles describing platelet transfusion policies in 483 GT-patients and 29 BSS-patients, both adults and children. Twenty surveys were returned for full analysis. All responders treated patients with platelet disorders, including GT (n = 36 reported) and BSS (n = 29 reported). Of respondents, 75% estimated the risk of antibody formation as "likely" for HLA and 65% for HPA. Formation of HLA antibodies was reported in 5 GT and in 5 BSS-patients, including one child. Fifteen respondents gave preventive HLA-matched platelets in elective setting (75%). Three respondents additionally matched for HPA in GT-patients (15%). Main argument for matched platelet transfusions was preventing alloimmunization to safeguard the effectivity of 'random' donor-platelets in acute settings. Elective HLA-matching for GT and BSS-patients is already conducted by most Dutch (pediatric) hematologists. HPA-matching is mainly applied when HPA-antibodies are formed. Based on the current literature and the survey, recommendations are proposed.

Pretransplant, Th17 dominant alloreactivity in highly sensitized kidney transplant candidates

IntroductionSensitization to donor human leukocyte antigen (HLA) molecules prior to transplantation is a significant risk factor for delayed access to transplantation and to long-term outcomes. Memory T cells and their cytokines play a pivotal role in shaping immune responses, thereby increasing the risk of allograft rejection among highly sensitized patients. This study aims to elucidate the precise contribution of different CD4+ memory T cell subsets to alloreactivity in highly sensitized (HS) kidney transplant recipients.Methods and resultsStimulation of peripheral blood mononuclear cells (PBMC) with various polyclonal stimulating agents to assess non-specific immune responses revealed that HS patients exhibit elevated immune reactivity even before kidney transplantation, compared to non-sensitized (NS) patients. HS patients' PBMC displayed higher frequencies of CD4+ T cells expressing IFNγ, IL4, IL6, IL17A, and TNFα and secreted relatively higher levels of IL17A and IL21 upon stimulation with PMA/ionomycin. Additionally, PBMC from HS patients stimulated with T cell stimulating agent phytohemagglutinin (PHA) exhibited elevated expression levels of IFNγ, IL4 and, IL21. On the other hand, stimulation with a combination of resiquimod (R848) and IL2 for the activation of memory B cells demonstrated higher expression of IL17A, TNFα and IL21, as determined by quantitative real-time PCR. A mixed leukocyte reaction (MLR) assay, employing third-party donor antigen presenting cells (APCs), was implemented to evaluate the direct alloreactive response. HS patients demonstrated notably higher frequencies of CD4+ T cells expressing IL4, IL6 and IL17A. Interestingly, APCs expressing recall HLA antigens triggered a stronger Th17 response compared to APCs lacking recall HLA antigens in sensitized patients. Furthermore, donor APCs induced higher activation of effector memory T cells in HS patients as compared to NS patients.ConclusionThese results provide an assessment of pretransplant alloreactive T cell subsets in highly sensitized patients and emphasize the significance of Th17 cells in alloimmune responses. These findings hold promise for the development of treatment strategies tailored to sensitized kidney transplant recipients, with potential clinical implications.

Immunology Status of Patients During Kidney Transplant.

The immunology status of a patient has a crucial role in kidney transplant. We investigated the effectiveness of a desensitization protocol, guided by the immunology status of patients, for kidney transplant candidates. Antibody screening for human leukocyte antigens was conducted with the Luminex single-antigen microsphere bead assay method for 34 patients from June 2021 to June 2022. Donor human leukocyte antigen genotypes at 8 loci (A*, B*, С*, DRB1*, DQA1*, DQB1*, DPA1*, and DPB1*) were determined, to correlate the specificities of recipient human leukocyte antigen antibodies with donor antigens and identify unacceptable donor antigen combinations. Specialized immunology studies measured panel reactive antibody levels and human leukocyte antigen class I and class II antibodies. A crossmatch compatibility test using complementdependent cytotoxicity was conducted. Of the 34 patients, 10 completed all 3 stages of the desensitization therapy. Most patients experienced decreased sensitization to human leukocyte antigen class I and class II antibodies. Two patients achieved complete clearance of A1 and DQ5 antibodies, respectively, whereas 1 patient exhibited an increase in donor-specific antibody mean fluorescence intensity. Prior to desensitization therapy, the crossmatch compatibility test yielded positive results with T and B lymphocytes. After completing the therapy, the crossmatch test showed negative results in 4 cases with T lymphocytes and positive results with B lymphocytes. Plasmapheresis sessions effectively reduced circulating antibodies. However, the combination of rituximab and plasmapheresis alone did not achieve a negative crossmatch test required for kidney transplant. It is crucial to assess the reduction of donor-specific antibody quantity, considering both the percentage and the mean fluorescence intensity. To avoid false-positive results in crossmatch analysis, drug half-life must be considered. Laboratories should have various crossmatch techniques, such as flow cytometry and single-antigen microsphere bead assay technology, available for research and urgent cases that require crossmatch analysis.

Tracking Circulating HLA-Specific IgG-Producing Memory B Cells with the B-Cell ImmunoSpot Assay.

Donor-specific antibodies (DSA) against human leukocyte antigen (HLA) molecules are a major risk factor for rejection of transplanted organs (in antibody-mediated rejection [ABMR]), particularly in patients who have prior sensitization or receive insufficient immunosuppression through minimization or noncompliance. These DSA are measured routinely in the serum of patients prior to transplantation mainly using bead-based technologies or cell-based assays. However, the absence of detectable serum DSA does not always reflect the absence of sensitization or histologically defined ABMR, and so it has been proposed that the detection and measurement of memory B cells capable of secreting antibodies against donor HLA antigens could be carried out using B-cell ImmunoSpot, to better inform the degree of immune sensitization of transplant patients prior to as well as after transplantation. Such an assay is described here.

HLA Typing and Donor-Specific Antibody Screening in Kidney Transplantation: Bridging the Past to the Future

Human leukocyte antigens (HLA) are unique proteins expressed on the surface of human cells, playing a pivotal role in the immune system, particularly in the contexts of infection, cancer, and transplantation. The widespread adoption of HLA typing methods has become an essential component in assessing donor-recipient compatibility, a crucial limiting factor in solid organ transplantation. In general, the greater the disparity between a donor's and recipient's HLA types, the higher the likelihood of provoking an alloimmune response, which frequently results in alloimmune graft rejection. With significant advancements in organ transplantation techniques, immunosuppressive medications, and surgical procedures, attention has increasingly turned toward understanding and managing humoral rejection processes. Pre-transplant antibody screening plays a critical role in identifying individuals with elevated levels of antibodies against potential donor antigens. This screening aids in risk assessment and planning to mitigate the risk of antibody-mediated rejection (AbMR). Several methods are available for assessing circulating antigen-specific antibodies and HLA tissue typing, including cell-based assays like serological assays, complement-dependent cytotoxicity, and flow cytometry. However, non-cell-based approaches, such as molecular methods, HLA imputation techniques and high-throughput HLA-matchmaker assays have gained significant popularity due to their ability to provide higher resolution and robust donor-recipient matching. Despite the advancements in precision and sensitivity observed in HLA cutting-edge technologies, numerous challenges still persist. These challenges involve complexities linked to allelic ambiguities, the differentiation of closely related alleles, and the ongoing effort to establish a standardized HLA testing methodology across diverse laboratories. Additionally, correlating the HLA crossmatch results with the clinical outcomes for transplant donors poses another important aspect that warrants attention and requires expert analysis. In this review, we will enumerate the different methods of HLA typing and DSA screening and discuss the unmet needs and future directions for HLA typing methods.

IgM marks persistent IgG anti-human leukocyte antigen antibodies in highly sensitized heart transplant patients

Sensitization to human leukocyte antigens (HLA) is a persistent problem in heart transplant (HT) candidates. We sought to characterize the anti-HLA antibody and circulating B cell repertoire in a cohort of highly sensitized HT candidates. We assessed IgG and IgM anti-HLA antibodies using luminex single antigen bead assays in a cohort of 11 highly sensitized (HS; calculated panel reactive antibody ≥ 90%) and 3 mildly sensitized (MS) candidates. We also performed B cell receptor repertoire sequencing (BCRseq) in HS candidates and 33 non-candidate controls. HLA antibody strength was measured by mean fluorescence intensity (MFI). We found that IgM anti-HLA antibodies were present in all HS candidates, but with a lower breadth and strength as compared to IgG. When anti-HLA IgG specificities intersected with IgM, binding strength was higher. In contrast, there were IgM but no intersecting IgG specificities for the MS group. In four candidates in the HS group, IgG anti-HLA antibodies decreased in both breadth and strength after HT, but the decrease in strength was smaller if the IgG possessed a specificity that intersected with pre-transplant IgM. BCRseq revealed larger B cell clonotypes in HS candidates but similar diversity as compared to controls. IgM marks IgG anti-HLA antibodies with higher strength before HT and persistence after HT. The presence of IgM intersecting IgG for an anti-HLA specificity may be useful approach to determine which donor HLA should be avoided for a sensitized candidate.

Management of donor-specific antibodies in lung transplantation

The formation of antibodies against donor human leukocyte antigens poses a challenging problem both for donor selection as well as postoperative graft function in lung transplantation. These donor-specific antibodies limit the pool of potential donor organs and are associated with episodes of antibody-mediated rejection, chronic lung allograft dysfunction, and increased mortality. Optimal management strategies for clearance of DSAs are poorly defined and vary greatly by institution; most of the data supporting any particular strategy is limited to small-scale retrospective cohort studies. A typical approach to antibody depletion may involve the use of high-dose steroids, plasma exchange, intravenous immunoglobulin, and possibly other immunomodulators or small-molecule therapies. This review seeks to define the current understanding of the significance of DSAs in lung transplantation and outline the literature supporting strategies for their management.

Preventing kidney transplant failure by screening for antibodies against human leucocyte antigens followed by optimised immunosuppression: OuTSMART RCT

Design Investigator-led, prospective, open-labelled marker-based strategy (hybrid) randomised trial. Background Allografts in 3% of kidney transplant patients fail annually. Development of antibodies against human leucocyte antigens is a validated predictive biomarker of allograft failure. Under immunosuppression is recognised to contribute, but whether increasing immunosuppression can prevent allograft failure in human leucocyte antigen Ab+ patients is unclear. Participants Renal transplant recipients > 1 year post-transplantation attending 13 United Kingdom transplant clinics, without specific exclusion criteria. Interventions Regular screening for human leucocyte antigen antibodies followed, in positive patients by interview and tailored optimisation of immunosuppression to tacrolimus, mycophenolate mofetil and prednisolone. Objective To determine if optimisation of immunosuppression in human leucocyte antigen Ab+ patients can cost-effectively prevent kidney allograft failure. Outcome Time to graft failure after 43 months follow-up in patients receiving the intervention, compared to controls, managed by standard of care. Costs and quality-adjusted life-years were used in the cost-effectiveness analysis. Randomisation and blinding Random allocation (1 : 1) to unblinded biomarker-led care or double-blinded standard of care stratified by human leucocyte antigen antibodies status (positive/negative) and in positives, presence of donor-specific antibodies (human leucocyte antigen antibodies against donor human leucocyte antigen) or not (human leucocyte antigen antibodies against non-donor human leucocyte antigen), baseline immunosuppression and transplant centre. Biomaker-led care human leucocyte antigen Ab+ patients received intervention. Human leucocyte antigen Ab-negative patients were screened every 8 months. Recruitment Began September 2013 and for 37 months. The primary endpoint, scheduled for June 2020, was moved to March 2020 because of COVID-19. Numbers randomised From 5519 screened, 2037 were randomised (1028 biomaker-led care, 1009 to standard of care) including 198 with human leucocyte antigen antibodies against donor human leucocyte antigen (106 biomaker-led care, 92 standard of care) and 818 with human leucocyte antigens antibodies against non-donor human leucocyte antigen (427 biomaker-led care, 391 standard of care). Numbers analysed Two patients were randomised in error so 2035 were included in the intention-to-treat analysis. Outcome The trial had 80% power to detect a hazard ratio of 0.49 in biomarker-led care DSA+ group, > 90% power to detect hazard ratio of 0.35 in biomarker-led care non-DSA+ group (with 5% type 1 error). Actual hazard ratios for graft failure in these biomarker-led care groups were 1.54 (95% CI: 0.72 to 3.30) and 0.97 (0.54 to 1.74), respectively. There was 90% power to demonstrate non-inferiority of overall biomarker-led care group with assumed hazard ratio of 1.4: This was not demonstrated as the upper confidence limit for graft failure exceeded 1.4: (1.02, 95% CI 0.72 to 1.44). The hazard ratio for biopsy-proven rejection in the overall biomarker-led care group was 0.5 [95% CI: 0.27 to 0.94: p = 0.03]. The screening approach was not cost-effective in terms of cost per quality-adjusted life-year. Harms No significant differences in other secondary endpoints or adverse events. Limitations Tailored interventions meant optimisation was not possible in some patients. We did not study pathology on protocol transplant biopsies in DSA+ patients. Conclusions No evidence that optimised immunosuppression in human leucocyte antigen Ab+ patients delays renal transplant failure. Informing patients of their human leucocyte antigen antibodies status appears to reduce graft rejection. Future work We need a better understanding of the pathophysiology of transplant failure to allow rational development of effective therapies. Trial registration This trial is registered as EudraCT (2012-004308-36) and ISRCTN (46157828). Funding This project was funded by the National Institute for Health and Care Research (NIHR) Efficacy and Mechanism Evaluation programme (11/100/34) and will be published in full in Efficacy and Mechanism Evaluation; Vol. 10, No. 5. See the NIHR Journals Library website for further project information.

Hybrid structural modeling of alloantibody binding to human leukocyte antigen with rapid and reproducible cross-linking mass spectrometry

Alloantibody recognition of donor human leukocyte antigen (HLA) is associated with poor clinical transplantation outcomes. However, the molecular and structural basis for the alloantibody-HLA interaction is not well understood. Here, we used a hybrid structural modeling approach on a previously studied alloantibody-HLA interacting pair with inputs from ab initio, in silico, and invitro data. Highly reproducible cross-linking mass spectrometry data were obtained with both discovery- and targeted mass spectrometry-based approaches approaches. The cross-link information was then used together with predicted antibody Fv structure, predicted antibody paratope, and in silico-predicted interacting surface to model the antibody-HLA interaction. This hybrid structural modeling approach closely recapitulates the key interacting residues from a previously solved crystal structure of an alloantibody-HLA-A∗11:01 pair. These results suggest that a predictive-based hybrid structural modeling approach supplemented with cross-linking mass spectrometry data can provide functionally relevant structural models to understand the structural basis of antibody-HLA mismatch in transplantation.

Selection and Interpretation of Molecular Diagnostics in Heart Transplantation.

The number of heart transplants performed annually in the United States and worldwide continues to increase, but there has been little change in graft longevity and patient survival over the past 2 decades. The reference standard for diagnosis of acute cellular and antibody-mediated rejection includes histologic and immunofluorescence evaluation of endomyocardial biopsy samples, despite invasiveness and high interrater variability for grading histologic rejection. Circulating biomarkers and molecular diagnostics have shown substantial predictive value in rejection monitoring, and emerging data support their use in diagnosing other posttransplant complications. The use of genomic (cell-free DNA), transcriptomic (mRNA and microRNA profiling), and proteomic (protein expression quantitation) methodologies in diagnosis of these posttransplant outcomes has been evaluated with varying levels of evidence. In parallel, growing knowledge about the genetically mediated immune response leading to rejection (immunogenetics) has enhanced understanding of antibody-mediated rejection, associated graft dysfunction, and death. Antibodies to donor human leukocyte antigens and the technology available to evaluate these antibodies continues to evolve. This review aims to provide an overview of biomarker and immunologic tests used to diagnose posttransplant complications. This includes a discussion of pediatric heart transplantation and the disparate rates of rejection and death experienced by Black patients receiving a heart transplant. This review describes diagnostic modalities that are available and used after transplant and the landscape of future investigations needed to enhance patient outcomes after heart transplantation.

The Rule of Rescue in the Era of Precision Medicine, HLA Eplet Matching, and Organ Allocation

Precision medicine can put clinicians in a position where they must act more as resource allocators than their traditional role as patient advocates. In the allocation of transplantable organs and tissues, the use of eplet matching will enhance precision medicine but, in doing so, generate a tension with the present reliance on rule of rescue and justice-based factors for allocations. Matching donor and recipient human leukocyte antigens (HLA) is shown to benefit virtually all types of solid organ transplants yet, until recently, HLA-matching has not been practical and was shown to contribute to ethnic/racial disparities in organ allocation. Recent advances using eplets from the HLA molecule has renewed the promise of such matching for predicting patient outcomes. The rule of rescue in organ allocation reflects a combination of ethical, policy, and legal imperatives. However, the rule of rescue can impede the allocation strategies adopted by professional medical associations and the optimal use of scarce transplant resources. While eplet-matching seeks to improve outcomes, it may potentially frustrate current ethics-motivated initiatives, established patient-practitioner relationships, and functional conventions in the allocation of medical resources such as organ and tissue transplants. Eplet-matching allocation schemes need to be carefully and collaboratively designed with clear, fair and equitable guidelines that complement functional conventions and maintain public trust.

Immobilization of Thai Population-specific Human Leukocyte Antigens on Magnetic Nanoparticles Integrated with Nuclear Magnetic Resonance Technology

Kidney disease, as a global health problem, can progress to kidney failure. Kidney transplantation is a treatment option for end-stage disease and an alternative to dialysis. Complement-dependent cytotoxicity tests and flow cytometry are methods used to test for compatibility between autoantibodies and donor recipient. Antibodies against donor human leukocyte antigens (HLAs), linked to hyperacute or severely acute rejection, frequently result in graft loss. Currently, fluorescent bead assay (Luminex^®) technology is used in Thailand for HLA–antibody typing tests. However, each test requires specific location and time, expensive equipment, and high costs. The goal of such research is that, HLA–antibody typing tests can be performed wherever it is the most convenient for recipients and hospitals. A further advantage is that the surgeon can perform a final test for confirmation before the surgery. Numerous technologies are currently available for this purpose. The focus of this study was on the Fe₃O₄ magnetic nanoparticles (MNPs) immobilized with HLAs frequently found in the Thai population. These were examined using nuclear magnetic resonance (NMR) to measure HLA antibody typing. MNPs have recently attracted considerable attention because of their strong magnetization and large surface areas. Immobilization reactions with antigens and the straightforward magnetic separation of MNPs are low-cost techniques. Hence, the commercialization of Fe₃O₄ MNPs is favorable. In this study, MNPs were functionalized with 3-aminopropyl triethoxysilane (APTES) in toluene and ethanol, and the nanoparticles were streptavidin activated after APTES treatment. A specific biotinylated HLA for the Thai population was used and immobilized on streptavidin. The MNPs were effectively immobilized. The magnetic properties can be modified by adding other ions to Fe₃O₄. We discovered that the shape and size variations of Fe₃O₄ MNPs may have an impact on the amount of functionalized and immobilized surface area.

Autoimmune HLA Alleles and Neoepitope Presentation Predict Post-Allogenic Transplant Relapse.

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) can cure patients with high-risk myelodysplastic syndromes (MDS) and acute myeloid leukemia (AML). However, many patients relapse or develop debilitating graft-versus-host disease. Transplant restores T-cell reactivity against tumor cells, implicating patient human leukocyte antigen (HLA)-dependent antigen presentation via the major histocompatibility complex as a determinant of response. We sought to identify characteristics of the HLA genotype that influence response in allo-HSCT patients. We collected HLA genotype and panel-based somatic mutation profiles for 55 patients with AML and MDS and available data treated at the University of California San Diego Moores Cancer Center between May 2012 and January 2019. We evaluated characteristics of the HLA genotype relative to relapse-free time and overall survival (OS) post-allo-HSCT using univariable and multivariable regression. In multivariable regression, the presence of an autoimmune allele was significantly associated with relapse-free time (hazard ratio [HR], 0.25; p = 0.01) and OS (HR, 0.16; p < 0.005). The better potential of the donor HLA type to present peptides harboring driver mutations trended toward better relapse-free survival (HR, 0.45; p = 0.07) and significantly correlated with longer OS (HR, 0.33; p = 0.01) though only a minority of cases had an HLA mismatch. In this single institution retrospective study of patients receiving allo-HSCT for relapsed AML/MDS, characteristics of an individual's HLA genotype (presence of an autoimmune allele and potential of the donor HLA to better present peptides representing driver mutations) were significantly associated with better outcomes. These findings suggest that HLA type may guide the optimal application of allo-HSCT and merit evaluation in larger cohorts. ClinicalTrials.gov Identifier: NCT02478931.

Luminex Crossmatch in Kidney Transplantation.

The introduction of the Luminex Crossmatch assay (LumXm) which uses Luminex bead technology, consists of extracting the donor's Human Leukocyte Antigen (HLA) molecules from their lymphocytes, and binding them to fluorescent beads that are put in contact with recipient's serum. HLA donor-specific antibodies (DSA) are detected using a fluorescent conjugate. The goal of our study is to determine the benefits of using LumXm in a renal transplantation algorithm. We tested 78 recipients' sera using the LumXm, and the results were compared with the Luminex single antigen bead assay (SAB) for all sera, as well as the Flow Cytometry Crossmatch (FCXM) for 46 sera. We compared our results with those of SAB using 3 cutoffs, the first being the manufacturer's criteria where sensitivity and specificity were at 62.5% and 91.3% respectively for HLA class 1, and 88.5% and 50.0% respectively for HLA class 2. When using the third cutoff criteria ( ≥2 Adjusted values + MFI (Mean fluorescence intensity) >500 + Neg MFI < 500), the sensitivity increased to 69.0% for HLA class 1 and decreased to 84.0% for HLA class 2, while the specificity increased for HLA class 1 and 2. When comparing with FCXM, the 3 assays agreed in 55.8% of results for class 1 and 2 alike. However, major discrepancies were found for two groups in HLA class 1 and one in HLA class 2. The LumXm when used with other techniques to overcome its' weak points, can provide an interesting insight into the patient's HLA-DSA profile.

Assessment of donor compatibility in human solid organ transplantation and evaluation of allogeneic responses using a novel humanized mouse model.

Abstract The end result of solid organ transplantation is dictated by selection of a well-matched donor, leading to allograft survival. An allogeneic immune response is the main immunological barrier for successful organ transplantation. Donor and recipient human leukocyte antigen (HLA) mismatching results in poor graft acceptance, inflammation and rejection. The current evaluations for donor-recipient HLA incompatibility does not provide adequate information on the immunogenicity of individual HLA mismatches and impact of non-HLA-related alloantigens, especially in vivo. Here we demonstrate a novel method for analysis of alloimmune responsiveness between donor and recipient in vivoby introducing a humanized mouse model. Using molecular, cellular, and genomic analyses, we demonstrated that a recipient’s personalized humanized mouse provided the most sensitive assessment of allogeneic responsiveness to potential donors. In our study, HLA typing and mixed lymphocyte reaction (MLR) for assessment of allogeneic response was indistinguishable between 2 related donors of the recipient. Contrastingly in recipient’s humanized mouse model, the donor selected by HLA typing induced the strongest allogeneic response with increased infiltration of cytotoxic GzmB +CD8 +T cells. Moreover, the same donor induced upregulation of genes involved in the allograft rejection identified by transcriptomic analysis of graft infiltrating CD45 +cells. Humanized mouse model determined the lowest degree of recipient-donor alloimmune response, allowing for better selection of donor and minimized immunological risk of allograft rejection in transplantation. This approach can be used to evaluate alloresponses in cell based therapies as well. This study was supported by research funding from the Carlos and Marguerite Mason Trust, and by U.S. National Institutes of Health, National Cancer Institute Grant CA 172230

Outcomes of ABO Incompatible Kidney Transplantation:A Single Center Experience

Background: Kidney transplantation (KT) is the treatment of choice for patients with end-stage renal disease (ESRD). General organ donor shortage remains an important limitation on KT, given the increasing number of patients waiting for transplantation. This has led to the adoption of different strategies to increase the pool of donors, such as ABO incompatible (ABOi) living KT. In this single center study, we retrospectively evaluated all donor/recipient pairs proposed for ABOi KT since the beginning of this transplantation program in our hospital in 2014. Methods: Between November 2014 and March 2022, 609 deceased donor and 223 living donor KT were performed in our center. Seventy-one donor/recipient pairs were proposed for ABOi KT and were evaluated for ABO/Rh group, Coombs tests, human leukocyte antigen (HLA) type I (A, B, C) and II (DR) high resolution genotyping and receptor to donor isoagglutinin titers and HLA antibodies. Recipients with immunoglobulins G (IgG) and/or M (IgM) isoagglutinin titers &gt; 1:512 and/or with HLA donor specific alloantibodies (DSAs) were excluded from the ABOi transplantation program. Isoagglutinins removal was performed recurring to therapeutic plasma exchange (TPE) and/or immunoadsorption techniques. Transplanted patients were evaluated for demographic data, diagnosis, relationship with donor, sessions of antibodies removal, pre- and post-KT isoagglutinin titers, graft function, transfusion support, significant complications and overall patient survival. Results: Eighteen patients (14 males and 4 females) were transplanted with an ABOi graft out of 71 ABOi studied pairs. Median baseline IgG and IgM isoagglutinin titers were 1:32 (min 1:2, max 1:256) and 1:8 (min 1:2, max 1:32), respectively. Fifteen patients (83.3%) had pre-KT TPE and/or immunoadsorption sessions for isoagglutinin removal (mean 2.4 ± 1.8 session per patient). Seven patients (36.8%) were submitted to post-KT TPE (mean 1.9 ± 3.2 session per patient). No acute antibody mediated rejection was observed and overall graft survival was 100% on a follow-up period between 3 and 92 months (47.6 ± 25.2 months). All patients were dialysis-free with serum creatinine steady levels (median 1.4 mg/dL) at 47.6 ± 25.2 months of follow up. Conclusion: These results confirm that ABOi KT is a viable treatment for patients with ESRD, thus expanding living donor pool and reducing access time to transplantation.

Modeling unrelated blood stem cell donor recruitment using simulated registrant cohorts: Assessment of human leukocyte antigen matching across ethnicity groups.

Human leukocyte antigen (HLA)-matched unrelated donors are not available for some patients considered for allogeneic hematopoietic cell transplantation, particularly among certain ethnic groups. Simulated recruitment modeling can inform efforts to find new matches for more patients. Simulated recruits were generated by assigning a pair of donor HLA haplotypes from historical data files and matched against HLA data of patient searches in the Canadian Blood Services Stem Cell Registry. Recruitment cohorts reflected the proportion of five specific ethnic groups in the 2016 Canadian census data. Novel 8/8 HLA matches between simulated recruits and patients increased linearly with larger recruitment cohorts. The proportion of novel 8/8 HLA matches from Caucasian, Hispanic, and Native American/First Nations recruits was equal to or greater than their relative proportion in the recruited cohort (match to: recruit ratio (MRR) ≥ 1). In contrast, African American and Asian & Pacific Islander recruits represented a smaller proportion of novel matches relative to their percentage of the recruited cohort (MRR <1). The proportion of novel 7/8 HLA-matches from each ethnic group was approximately the same as their proportion in the recruited cohort (MRR ~ 1) and high rates of 7/8 HLA-matching already exist within the Canadian Blood Services registry for all ethnic groups. Continued large recruitment cohorts are needed to add new 8/8 HLA matches to registry inventories. Likelihoods of novel HLA matches varied across ethnic groups, reflecting varied HLA haplotype frequencies across groups. Simulated cohort modeling can inform recruitment strategies that will generate new donor options for patients.

Extended genomic HLA typing identifies previously unrecognized mismatches in living kidney transplantation.

Antibody mediated rejection (ABMR) is the most common cause of long-term allograft loss in kidney transplantation (KT). Therefore, a low human leukocyte antigen (HLA) mismatch (MM) load is favorable for KT outcomes. Hitherto, serological or low-resolution molecular HLA typing have been adapted in parallel. Here, we aimed to identify previously missed HLA mismatches and corresponding antibodies by high resolution HLA genotyping in a living-donor KT cohort. 103 donor/recipient pairs transplanted at the University of Leipzig Medical Center between 1998 and 2018 were re-typed using next generation sequencing (NGS) of the HLA loci -A, -B, -C, -DRB1, -DRB345, -DQA1, -DQB1, -DPA1, and -DPB1. Based on these data, we compiled HLA MM counts for each pair and comparatively evaluated genomic HLA-typing with pre-transplant obtained serological/low-resolution HLA (=one-field) typing results. NGS HLA typing (=two-field) data was further used for reclassification of de novo HLA antibodies as "donor-specific". By two-field HLA re-typing, we were able to identify additional MM in 64.1% (n=66) of cases for HLA loci -A, -B, -C, -DRB1 and -DQB1 that were not observed by one-field HLA typing. In patients with biopsy proven ABMR, two-field calculated MM count was significantly higher than by one-field HLA typing. For additional typed HLA loci -DRB345, -DQA1, -DPA1, and -DPB1 we observed 2, 26, 3, and 23 MM, respectively. In total, 37.3% (69/185) of de novo donor specific antibodies (DSA) formation was directed against these loci (DRB345 ➔ n=33, DQA1 ➔ n=33, DPA1 ➔ n=1, DPB1 ➔ n=10). Our results indicate that two-field HLA typing is feasible and provides significantly more sensitive HLA MM recognition in living-donor KT. Furthermore, accurate HLA typing plays an important role in graft management as it can improve discrimination between donor and non-donor HLA directed cellular and humoral alloreactivity in the long range. The inclusion of additional HLA loci against which antibodies can be readily detected, HLA-DRB345, -DQA1, -DQB1, -DPA1, and -DPB1, will allow a more precise virtual crossmatch and better prediction of potential DSA. Furthermore, in living KT, two-field HLA typing could contribute to the selection of the immunologically most suitable donors.

Donor-Specific Antibody Detection by Single-Antigen Bead Assay for Renal Transplantation: A 2-Year Experience from South India.

Recipient sensitization against donor human leukocyte antigens (HLA) plays a key role in transplant rejection, and this risk is best minimized by efficient pre transplant antibody detection. Determination of antibody specificity with the highest sensitivity and degree of resolution to the allelic antigen level is achieved by using single-antigen bead (SAB) assay. This study evaluated the correlation of Luminex cross match (LXM) with SAB assay for detection of donor-specific antibodies (DSA). A total of 2075 renal transplant patients were screened for the presence of DSA by LXM, complement-dependent cytotoxicity (CDC) cross match, and 125 patients for SAB from January 2018 to December 2019. There was a male preponderance among recipients (P < 0.0001), and the most affected age group was 21-40 years. HLA typing was done in 550/2075 by DNA PCR-reverse sequence-specific oligonucleotide probes (SSOP) method. HLA DSA by LXM was detected in 16.3% of recipients (338/2075). Majority 180/338 (53.2%) of the patients were class II DSA positive, (P < 0.0001). Among the class II DSA positive patients, 20/180 (11.1%) samples gave false-positive results by LXM. SAB for class I and class II HLA IgG antibodies was done in 125/338 renal transplant recipients, which included 20 recipients with false-positive class II Luminex DSA, to check whether the DSA detected were really donor specific or not. The results showed that although 20/125 patients had some antibodies detected in their serum, they were not against the donor HLA antigens, as per the HLA typing reports of the donors. When compared to SAB assay, LXM showed more discrepant results, particularly to class II DSA. In conclusion, LXM, if used in combination with SAB assay and HLA typing of donors if necessary for virtual cross match, will help in avoiding unnecessary exclusion of donors for renal transplant recipients and also for post transplant monitoring of recipients, especially in cadaveric donor transplants.

A retrospective study to assess the impact of ABO incompatibility on outcomes of allogeneic peripheral blood stem cell transplants at a tertiary care hospital in Western Maharashtra.

Hematopoietic stem cell transplantation (HSCT) has emerged as a curative measure for life-threatening hematological disorders. It can be autologous or allogeneic depending on the disease characteristics. Providing transfusion support to the transplant patients can be challenging, especially in AB-mismatched allogeneic HSCT. In this study, we investigated the impact of ABO incompatibility in patients undergoing allogeneic HSCT. A retrospective review was conducted in 76 patients with hematological diseases who underwent allogeneic HSCT. Transfusion requirements, engraftment profile, incidence of graft versus host disease (GvHD), and mortality for a period of 1 year were analyzed. ABO incompatibility between donor and the patient did not significantly affect the neutrophil and platelet (PLT) engraftment time (P = 0.389, 0.349, respectively), packed red blood cells transfusion requirement, and duration of initial hospital stay. However, patients of ABO-incompatible HSCT received more PLT transfusions posttransplant which was statistically significant. 29.1% of ABO compatible and 16.7% incompatible HSCT patients developed GVHD. Mortality rates in the two groups were 16.7% and 8.3%, respectively. However, differences in both the parameters were not statistically significant. Our study showed that ABO incompatibility does not significantly affect the outcome and should not be a limiting factor for selection of donor. Donor availability and human leukocyte antigen (HLA) matching remain the critical selection criteria.