Exploring the immunological relevance of pre-transplant donor-specific antibody in intestinal transplantation, with special consideration to the liver

Despite recent advances that have improved outcomes following intestinal transplantation (ITx), achieving long-term patient survival and rejection-free survival is still challenging. Understanding the relevance of pre-transplant human leukocyte antigen (HLA) donor-specific antibody (DSA) in ITx and the immunomodulatory potential of the liver within the allograft is crucial to providing an accurate assessment of pre-transplant immunological risk, which could influence and improve post-transplant outcomes further. This was the primary objective of this retrospective study of 95 adult ITx transplants which took place at Cambridge University Hospitals (United Kingdom) between 2007 and 2019. Two novel programs were developed and validated to identify DSA (tested by Luminex single antigen beads) in this dataset. Data analysis utilised Kaplan-Meier survival methods, and statistical analysis was performed using log-rank tests and adjusted Cox models. Fifty-four (57%) ITx cases contained a liver, and 36 (38%) were sensitised to HLA. Pre-transplant DSA > 500 mean fluorescent intensity appeared to negatively affect post-ITx patient survival and rejection outcomes. Additionally, liver-inclusive allografts seemed to show particular resistance to HLA class I DSA. Our data hints towards consistency with other ITx studies where deleterious effects of DSA have been demonstrated, and where liver inclusion is protective from HLA class I DSA. This is in line with current national guidelines for immunological risk. Our publicly available research programs could support future large or multicentre studies where statistically relevant data might be gained.

Forming a new perspective: Post-structural approaches to determination of donor compatibility and post-transplant assessment of allograft health

The purpose of this review is to encourage a new perspective on the question of donor-recipient compatibility and post-transplant assessment of graft health based on functional measures. The premise is that we should be better sighted on what (and how) the immune system responds toward rather than what is merely there. Continuance of the pursuit of further and better definition of antigens and antibodies is not however discouraged but seen as necessary to improved understanding of the structural correlates of functional immunity. There currently exists, in the opinion of the authors, an opportunity for histocompatibility and immunogenetics laboratories to develop and widen their scope of involvement into these new areas of laboratory activity in support and to the benefit of the transplant programmes they serve.

Histocompatibility assessment in hematopoietic stem cell transplantation: recommendations from the Italian Society for Immunogenetics and Transplantation Biology (Associazione Italiana di Immunogenetica e Biologia dei Trapianti - AIBT)

The outcome of allogeneic hematopoietic stem cell transplantation (HSCT) is significantly influenced by the degree of HLA histocompatibility between donor and recipient. To provide shared indications for required histocompatibility testing and interpretation before HSCT, the Italian Society for Immunogenetics and Transplantation Biology (Associazione Italiana di Immunogenetica e Biologia dei Trapianti [AIBT]) gathered members and created a working group to discuss and develop recommendations for histocompatibility assessment in HSCT.After a review of the literature and multiple panel discussions, AIBT developed up-to-date recommendations for the resolution levels of HLA typing, histocompatibility definitions of patients and donors, importance of anti-HLA antibodies, and significance of NK alloreactivity, which are reported in this document. These recommendations have been shared with the Italian Group for Bone Marrow Transplantation (Gruppo Italiano per il Trapianto di Midollo Osseo, cellule staminali emopoietiche e terapia cellulare [GITMO]) and the Italian National Center for Transplantation (Centro Nazionale Trapianti [CNT]). Notably, the increased use of HLA-mismatched transplantation (i.e., mismatched unrelated, haploidentical) in recent years has made these indications even more relevant for the standardization and improvement of quality of care.This document represents a useful instrument for health care workers involved in the field of HSCT, enhancing synergy with transplant physicians and enabling greater optimization of the available resources.

Microbiota dictate T cell clonal selection to augment graft-versus-host disease after stem cell transplantation

Allogeneic T cell expansion is the primary determinant of graft-versus-host disease (GVHD), and current dogma dictates that this is driven by histocompatibility antigen disparities between donor and recipient. This paradigm represents a closed genetic system within which donor T cells interact with peptide-major histocompatibility complexes (MHCs), though clonal interrogation remains challenging due to the sparseness of the T cell repertoire. We developed a Bayesian model using donor and recipient T cell receptor (TCR) frequencies in murine stem cell transplant systems to define limited common expansion of T cell clones across genetically identical donor-recipient pairs. A subset of donor CD4+ T cell clonotypes differentially expanded in identical recipients and were microbiota dependent. Microbiota-specific T cells augmented GVHD lethality and could target microbial antigens presented by gastrointestinal epithelium during an alloreactive response. The microbiota serves as a source of cognate antigens that contribute to clonotypic T cell expansion and the induction of GVHD independent of donor-recipient genetics.

Impact of a positive crossmatch on pediatric heart transplant outcomes

BACKGROUND

Pediatric heart transplant (HT) candidates experience high waitlist mortality due to a limited donor pool that is constrained in part by anti-HLA sensitization. We evaluated the impact of CDC and Flow donor-specific crossmatch (XM) results on pediatric HT outcomes.

METHODS

All pediatric HTs between 1999 and 2019 in the OPTN database were included. Donor-specific XM results were sub-categorized based on CDC and Flow results. Primary outcomes were treated rejection in the first year and time to death or allograft loss. Propensity scores were utilized to adjust for differences in baseline characteristics.

RESULTS

A total of 4,695 pediatric HT patients with T-cell XM data were included. After propensity score adjustment, a positive T-cell CDC-XM was associated with 2 times higher odds of treated rejection (OR 2.29 (1.56, 3.37)) and shorter time to death/allograft loss (HR 1.50 (1.19, 1.88)) compared to a negative Flow-XM. HT recipients who were Flow-XM positive with negative/unknown CDC-XM did not have higher odds of rejection or shorter time to death/allograft loss. An isolated positive B-cell XM was also not associated with worse outcomes. Over the study period XM testing shifted from CDC- to Flow-based assays.

CONCLUSIONS

A positive donor-specific T-cell CDC-XM was associated with rejection and death/allograft loss following pediatric HT. This association was not observed with a positive T-cell Flow-XM or B-cell XM result alone. The shift away from performing the CDC-XM may result in loss of important prognostic information unless the clinical relevance of quantitative Flow-XM results on heart transplant outcomes is systematically studied.

Predicting flow cytometry crossmatch results from single-antigen bead testing

The aim of this study was to devise an algorithm that would predict flow cytometry crossmatch (FCXM) results using single-antigen bead (SAB) mean fluorescent intensity (MFI) levels using samples received through the National External Quality Assurance Scheme (NEQAS) 2B external proficiency testing scheme between 2019 and 2023. A total of 159 serum samples were retrospectively screened using LABScreen Single Antigen Class I and II (SAB), and 40 peripheral blood samples were human leucocyte antigen (HLA) typed with LABType SSO. Donor-specific antibodies were identified for each cell-serum combination tested, and cumulative MFI values were calculated for each test before correlating the screening result with the consensus crossmatch results for this scheme. HLA Class I MFIs were combined to predict the T cell crossmatch. For the B cell crossmatch prediction, two options were considered: (i) HLA Class II MFI values alone and (ii) HLA Class I + Class II MFIs. Receiver operating characteristic analysis was carried out to identify the combined MFI threshold that predicted NEQAS consensus results with the greatest sensitivity and specificity. HLA Class I combined MFI >5000 predicted T cell crossmatch results with 96% sensitivity, 100% specificity, 100% positive predictive value (PPV) and 92% negative predictive value (NPV). For B cell results, HLA Class I + Class II combined MFIs >11,000 gave the best model, showing 97% sensitivity, 82% specificity, 96% PPV and 85% NPV. However, for samples with only HLA Class II sensitization, combined MFIs >13,000 improved the B cell crossmatch predictions: 92% sensitivity, 95% specificity, 96% PPV and 91% NPV. Using this model, combined MFI can be used to predict the immunological risk posed by donor-specific antibodies when it is not possible to carry out an FCXM.

Qualitative, rather than quantitative, differences between HLA-DQ alleles affect HLA-DQ immunogenicity in organ transplantation

Prolonging the lifespan of transplanted organs is critical to combat the shortage of this life-saving resource. Chronic rejection, with irreversible demise of the allograft, is often caused by the development of donor-specific HLA antibodies. Currently, enumerating molecular (amino acid) mismatches between recipient and donor is promoted to identify patients at higher risk of developing HLA antibodies, for use in organ allocation, and immunosuppression-minimization strategies. We have counseled against the incorporation of such approaches into clinical use and hypothesized that not all molecular mismatches equally contribute to generation of donor-specific immune responses. Herein, we document statistical shortcomings in previous study design: for example, use of individuals who lack the ability to generate donor-specific-antibodies (HLA identical) as part of the negative cohort. We provide experimental evidence, using CRISPR-Cas9-edited cells, to rebut the claim that the HLAMatchmaker eplets represent "functional epitopes." We further used unique sub-cohorts of patients, those receiving an allograft with two HLA-DQ mismatches yet developing antibodies only to one mismatch (2MM1DSA), to interrogate differential immunogenicity. Our results demonstrate that mismatches of DQα05-heterodimers exhibit the highest immunogenicity. Additionally, we demonstrate that the DQα chain critically contributes to the overall qualities of DQ molecules. Lastly, our data proposes that an augmented risk to develop donor-specific HLA-DQ antibodies is dependent on qualitative (evolutionary and functional) divergence between recipient and donor, rather than the mere number of molecular mismatches. Overall, we propose an immunological mechanistic rationale to explain differential HLA-DQ immunogenicity, with potential ramifications for other pathological processes such as autoimmunity and infections.

Evaluation of 19 years of international external proficiency testing for high-resolution HLA typing

The international high-resolution external proficiency testing (EPT) started in 2004 with high-resolution typing of human leucocyte antigen (HLA) class I (HLA-A,B,C) and HLA class II (HLA-DRB1, DRB345, DQB1, and DPB1) alleles, since possibilities for such an EPT within Europe were limited and all existing EPTs at that time made use of the comparison of HLA typing results without a reference. This EPT was set up as a collaboration between the HLA laboratory of Leiden, providing DNA samples to the participants, and the laboratory of Maastricht, performing the high-resolution typing as the reference result and evaluating the results of all participants according to the prevailing European Federation for Immunogenetics (EFI) standards. Once a year, 12 samples were sent to the participating laboratories, and evaluation and certificates were provided at the end of that same year. During the years, the EPT was extended to low-resolution HLA class I and II typing, high-resolution typing including DQA1 and DPA1, and allelic resolution typing for HLA class I, the latter one being unique in this field. Evaluation of the high-resolution typing results of the last 19 years showed a clear increase in the number of loci tested by the participating laboratories and a clear change of method from Sanger sequencing with additional other techniques (SSO/SSP) to the nowadays widely used next-generation sequencing method. By strictly using the EFI rules for high-resolution HLA typing, the participants were made aware of the ambiguities within exons 2 and 3 for class I and exon 2 for class II and the presence of null alleles even in a two-field HLA typing. There was an impressive learning curve, resulting in >98% correctly typed samples since 2017 and a 100% fulfillment of EFI rules for all laboratories for all loci submitted in the last 2 years. Overall, this EPT meets the need of an EPT for high-resolution typing for EFI accreditation.

UK NEQAS and BSHI guideline: Laboratory testing and clinical interpretation of HLA genotyping results supporting the diagnosis of coeliac disease

Coeliac disease is a common immune-mediated inflammatory disorder caused by dietary gluten in genetically susceptible individuals. While the diagnosis of coeliac disease is based on serological and histological criteria, HLA-DQ genotyping can be useful, especially in excluding the diagnosis in patients who do not carry the relevant DQ heterodimers: DQA1*05 DQB1*02, DQB1*03:02 or DQA1*02 DQB1*02 (commonly referred to as DQ2.5, DQ8 and DQ2.2, respectively). External quality assessment results for HLA genotyping in coeliac disease have revealed concerning errors in HLA genotyping, reporting and clinical interpretation. In response, these guidelines have been developed as an evidence-based approach to guide laboratories undertaking HLA genotyping for coeliac disease and provide recommendations for reports to standardise and improve the communication of results.

Improving HLA typing imputation accuracy and eplet identification with local next-generation sequencing training data

Assessing donor/recipient HLA compatibility at the eplet level requires second field DNA typings but these are not always available. These can be estimated from lower-resolution data either manually or with computational tools currently relying, at best, on data containing typing ambiguities. We gathered NGS typing data from 61,393 individuals in 17 French laboratories, for loci A, B, and C (100% of typings), DRB1 and DQB1 (95.5%), DQA1 (39.6%), DRB3/4/5, DPB1, and DPA1 (10.5%). We developed HaploSFHI, a modified iterative maximum likelihood algorithm, to impute second field HLA typings from low- or intermediate-resolution ones. Compared with the reference tools HaploStats, HLA-EMMA, and HLA-Upgrade, HaploSFHI provided more accurate predictions across all loci on two French test sets and four European-independent test sets. Only HaploSFHI could impute DQA1, and solely HaploSFHI and HaploStats provided DRB3/4/5 imputations. The improved performance of HaploSFHI was due to our local and nonambiguous data. We provided explanations for the most common imputation errors and pinpointed the variability of a low number of low-resolution haplotypes. We thus provided guidance to select individuals for whom sequencing would optimize incompatibility assessment and cost-effectiveness of HLA typing, considering not only well-imputed second field typing(s) but also well-imputed eplets.

A registry-based population study of the HLA in Québec, Canada

As part of the worldwide effort to better characterize HLA diversity in populations, we have studied the population of Québec in Canada. This province has been defined by a complex history with multiple founder effects and migration patterns. We analyzed the typing data of 3806 individuals registered in Héma-Québec's Registry, which covered most administrative regions in Québec. Typing information was resolved at the second field level of resolution by next-generation sequencing (NGS) or by Sanger sequencing. We used the HLA-net.eu GENE[RATE] tools to estimate allele and two-locus haplotype frequencies for HLA-A, -B, -C, -DRB1, -DQB1, and -DPB1, as well as Hardy-Weinberg equilibrium (HWE), selective neutrality, and linkage disequilibrium. The chord genetic distance was also calculated between administrative regions and was visualized using non-metric multidimensional scaling (NMDS) analysis. While most individual regions were in HWE, HWE was rejected for the province considered as a whole. Some regions exhibited signatures of selection, mostly toward an excess of heterozygotes. Allele and haplotype frequencies revealed outlier regions that strongly differed from the other regions. NMDS plots also showed differences between regions. The administrative regions of the province of Québec displayed heterogeneity in their HLA profiles. This heterogeneity was attributable to differing allele and haplotype specificities by region. In particular, regions 02-Saguenay-Lac-Saint-Jean and 01-Bas-St-Laurent diverged from the rest of the regions. The urban regions 06-Montréal and 13-Laval were very diversified in their HLA profiles. Together, these results will help optimize donor recruitment strategies in Québec.

A rational approach to guide cost-effective de novo donor-specific antibody surveillance with tacrolimus immunosuppression

De novo donor-specific antibody (dnDSA) after renal transplantation has been shown to correlate with antibody-mediated rejection and allograft loss. However, the lack of proven interventions and the time and cost associated with annual screening for dnDSA are difficult to justify for all recipients. We studied a well-characterized consecutive cohort (n = 949) with over 15 years of prospective dnDSA surveillance to identify risk factors that would help institute a resource-responsible surveillance strategy. Younger recipient age and HLA-DR/DQ molecular mismatch were independent predictors of dnDSA development. Combining both risk factors into recipient age molecular mismatch categories, we found that 52% of recipients could be categorized as low-risk for dnDSA development (median subclinical dnDSA-free survival at 5 and 10 years, 98% and 97%, respectively). After adjustment, multivariate correlates of dnDSA development included tacrolimus versus cyclosporin maintenance immunosuppression (hazard ratio [HR], 0.37; 95% CI, 0.2-0.6; P < .0001) and recipient age molecular mismatch category: intermediate versus low (HR, 2.48; 95% CI, 1.5-4.2; P = .0007), high versus intermediate (HR, 2.56; 95% CI, 1.6-4.2; P = .0002), and high versus low (HR, 6.36; 95% CI, 3.7-10.8; P < .00001). When combined, recipient age and HLA-DR/DQ molecular mismatch provide a novel data-driven approach to reduce testing by >50% while selecting those most likely to benefit from dnDSA surveillance.

BSHI and BTS UK guideline on the detection of alloantibodies in solid organ (and islet) transplantation

Solid organ transplantation represents the best (and in many cases only) treatment option for patients with end-stage organ failure. The effectiveness and functioning life of these transplants has improved each decade due to surgical and clinical advances, and accurate histocompatibility assessment. Patient exposure to alloantigen from another individual is a common occurrence and takes place through pregnancies, blood transfusions or previous transplantation. Such exposure to alloantigen's can lead to the formation of circulating alloreactive antibodies which can be deleterious to solid organ transplant outcome. The purpose of these guidelines is to update to the previous BSHI/BTS guidelines 2016 on the relevance, assessment, and management of alloantibodies within solid organ transplantation.

Impact of allele-specific anti-human leukocyte antigen class I antibodies on organ allocation

Technological advances in the field of histocompatibility have allowed us to define anti-human leukocyte antigen (HLA) antibody specificity at the allelic level. However, how allele-specific antibodies affect organ allocation is poorly studied. We examined allelic specificities of class I HLA antibodies in 6726 consecutive serum samples from 2953 transplant candidates and evaluated their impact on the corresponding crossmatch and organ allocation. Out of 17 class I HLA antigens represented by >1 allele in the LABScreen single antigen bead assay, 12 had potential allele-specific reactivity. Taking advantage of our unbiased cohort of deceased donor-candidate testing (123,135 complement-dependent cytotoxicity crossmatches between 2014 and 2017), we estimated that the presence of allele-specific antibody detected using a single antigen bead assay (median fluorescence intensity, >3000) against only the rare allele was a poor predictor of a positive complement-dependent cytotoxicity crossmatch, with a positive predictive value of 0% to 7%, compared with 52.5% in allele-concordant class I HLA antibodies against A or B locus antigens. Further, we confirmed allele-specific reactivity using flow crossmatch in 3 scenarios: A11:01/A11:02, A68:01/A68:02, and B44:02/B44:03. Our results suggest that allele-specific antibodies may unnecessarily exclude transplant candidates (up to 10%) from organ offers by overcalling unacceptable antigens; incorporation of selective reactivity pattern in allocation may promote precision matching and more equitable allocation.

A paired-kidney allocation study found superior survival with HLA-DR compatible kidney transplants in the Eurotransplant Senior Program

The Eurotransplant Senior Program (ESP) has expedited the chance for elderly patients with kidney failure to receive a timely transplant. This current study evaluated survival parameters of kidneys donated after brain death with or without matching for HLA-DR antigens. This cohort study evaluated the period within ESP with paired allocation of 675 kidneys from donors 65 years and older to transplant candidates 65 years and older, the first kidney to 341 patients within the Eurotransplant Senior DR-compatible Program and 334 contralateral kidneys without (ESP) HLA-DR antigen matching. We used Kaplan-Meier estimates and competing risk analysis to assess all cause mortality and kidney graft failure, respectively. The log-rank test and Cox proportional hazards regression were used for comparisons. Within ESP, matching for HLA-DR antigens was associated with a significantly lower five-year risk of mortality (hazard ratio 0.71; 95% confidence interval 0.53-0.95) and significantly lower cause-specific hazards for kidney graft failure and return to dialysis at one year (0.55; 0.35-0.87) and five years (0.73; 0.53-0.99) post-transplant. Allocation based on HLA-DR matching resulted in longer cold ischemia (mean difference 1.00 hours; 95% confidence interval: 0.32-1.68) and kidney offers with a significantly shorter median dialysis vintage of 2.4 versus 4.1 yrs. in ESP without matching. Thus, our allocation based on HLA-DR matching improved five-year patient and kidney allograft survival. Hence, our paired allocation study suggests a superior outcome of HLA-DR matching in the context of old-for-old kidney transplantation.

Antibody Therapeutics as Interfering Agents in Flow Cytometry Crossmatch for Organ Transplantation

Donor-recipient matching is a highly individualized and complex component of solid organ transplantation. Flowcytometry crossmatching (FC-XM) is an integral step in the matching process that is used to detect pre-formed deleterious anti-donor immunoglobulin. Despite high sensitivity in detecting cell-bound immunoglobulin, FC-XM is not able to determine the source or function of immunoglobulins detected. Monoclonal antibody therapeutic agents used in a clinic can interfere with the interpretation of FC-XM. We combined data from the prospectively maintained Antibody Society database and Human Protein Atlas with a comprehensive literature review of PubMed to summarize known FC-XM-interfering antibody therapeutics and identify potential interferers. We identified eight unique FC-XM-interfering antibody therapeutics. Rituximab (anti-CD20) was the most-cited agent. Daratumuab (anti-CD38) was the newest reported agent. We identified 43 unreported antibody therapeutics that may interfere with FC-XM. As antibody therapeutic agents become more common, identifying and mitigating FC-XM interference will likely become an increased focus for transplant centers.

Hilliard Seigler, M.D. and the origins of kidney transplantation and immunology at Duke

The contributions of Dr. Hilliard Seigler to the founding of the Duke kidney transplantation program were considerable in both surgery and immunology. Some of these highlights are summarized based upon interviews with Dr. Seigler by the authors.

Rheumatoid arthritis-associated antibodies in healthy first-degree relatives of RA patients

Rheumatoid arthritis (RA) affects approximately 1.5% of the population worldwide and 0.5-3.3% of the Mexican population. The presence of rheumatoid factor (RF), anti-citrullinated protein antibodies (ACPA) and anti-carbamylated protein (anti-CarP) antibodies has been described in populations at risk of RA development, such as first-degree relatives (FDR). Anti-CarP antibodies are present in RA patients (44%), FDR of RA patients (18%) and healthy controls (4.7%). Anti-CarP antibodies have not been described in FDR of the Mexican population. The objective of this study was to determine the prevalence of Rheumatoid Factors (RF) isotypes, ACPA and anti-CarP antibodies isotypes in FDR of RA patients. An observational, cross-sectional study, in an FDR of RA cohort, was performed. We measured IgA, IgG and IgM isotypes of RF, ACPA and anti-CarP antibodies. A total of 144 FDRs from 99 RA patients were enrolled. The prevalence of anti-CarP antibodies was 2.8% for IgA, 4.2% for IgG, whereas IgM was not detected. The serologic association was for RF/ACPA 4.48%, RF/anti-CarP 2.7%, FR 64.5%, ACPA 1.3%, ACPA/anti-CarP 0.69%, anti-CarP 3.4%, and no RF/ACPA/anti-CarP was observed. We found a low prevalence of anti-CarP antibodies in our cohort of FDR of RA patients, but the prevalence of ACPA and RF were higher than other cohorts previously reported.

First use of imlifidase desensitization in a highly sensitized lung transplant candidate: a case report

Lung transplant candidates who are highly sensitized against human leucocyte antigen present an ongoing challenge with regards to finding immunologically acceptable donors. Desensitization strategies aimed at reducing preformed donor-specific antibodies have a number of limitations. Imlifidase, an IgG-degrading enzyme derived from Streptococcus pyogenes, is a novel agent that has been used to convert positive crossmatches to negative in kidney transplant candidates, allowing transplantation to occur. We present the first case of imlifidase use for antibody depletion in a highly sensitized lung transplant candidate who went on to undergo a successful bilateral lung transplant.

Clinical recommendations for posttransplant assessment of anti-HLA (Human Leukocyte Antigen) donor-specific antibodies: A Sensitization in Transplantation: Assessment of Risk consensus document

Although anti-HLA (Human Leukocyte Antigen) donor-specific antibodies (DSAs) are commonly measured in clinical practice and their relationship with transplant outcome is well established, clinical recommendations for anti-HLA antibody assessment are sparse. Supported by a careful and critical review of the current literature performed by the Sensitization in Transplantation: Assessment of Risk 2022 working group, this consensus report provides clinical practice recommendations in kidney, heart, lung, and liver transplantation based on expert assessment of quality and strength of evidence. The recommendations address 3 major clinical problems in transplantation and include guidance regarding posttransplant DSA assessment and application to diagnostics, prognostics, and therapeutics: (1) the clinical implications of positive posttransplant DSA detection according to DSA status (ie, preformed or de novo), (2) the relevance of posttransplant DSA assessment for precision diagnosis of antibody-mediated rejection and for treatment management, and (3) the relevance of posttransplant DSA for allograft prognosis and risk stratification. This consensus report also highlights gaps in current knowledge and provides directions for clinical investigations and trials in the future that will further refine the clinical utility of posttransplant DSA assessment, leading to improved transplant management and patient care.

Improving equity in kidney transplant allocation policies through a novel genetic metric: The Matched Donor Potential

The demand for donors' kidneys continues to increase amid a shortage of available donors. Managing policies to thoughtfully allocate this scarce resource is a complex process. Although human leukocyte antigen (HLA) matching has been shown to prolong graft survival, its relative contribution to allocation schemes is empirically compromised owing to competing priorities. We explored using a new metric, Matched Donor Potential (MDP), to facilitate improved HLA matching while promoting equity. We interrogated all active kidney waitlist patients (N = 164 427), their corresponding unacceptable antigen files, and all effective donors in the Scientific Registry of Transplant Recipients (January 1, 2016-December 31, 2017). Cause-specific hazard functions were evaluated to assess the potential impact of the MDP metric on deceased donor transplant access rates for all candidates. Access was affected by ethnicity, blood group type, and calculated Panel Reactive Antibody (cPRA). Importantly, we show that access to transplantation is influenced by the patient's own HLA makeup regardless of their ethnicity and by the HLA makeup of effective donors. The MDP metric demonstrates a high association with access to transplantation. Adjusting Cox models to include this new metric resulted in improved access to kidney transplantation for waitlist candidates of minority heritage while significantly promoting HLA matching. Thus, the MDP metric accounts for balanced, equitable organ allocation algorithms.

Sensitization in transplantation: Assessment of Risk 2022 Working Group Meeting Report

The Sensitization in Transplantation: Assessment of Risk workgroup is a collaborative effort of the American Society of Transplantation and the American Society of Histocompatibility and Immunogenetics that aims at providing recommendations for clinical testing, highlights gaps in current knowledge, and proposes areas for further research to enhance histocompatibility testing in support of solid organ transplantation. This report provides updates on topics discussed by the previous Sensitization in Transplantation: Assessment of Risk working groups and introduces 2 areas of exploration: non-human leukocyte antigen antibodies and utilization of human leukocyte antigen antibody testing measurement to evaluate the efficacy of antibody-removal therapies.

Role of HLA typing and chimerism analysis in post-liver transplantation GVHD in pediatrics: A systematic review

BACKGROUND

GVHD is a well-documented complication after liver transplantation. GVHD occurs when donor immune cells mount a destructive immune response against host cells. The rarity of the GVHD complication and the nonspecific presentation of symptoms and histopathological features provide a diagnostic challenge. Therefore, diagnosis and initiation of treatment are often delayed.

AIM

In this systematic review, we assessed relevant literature to better understand the utilization of HLA typing and chimerism analysis in liver transplantation. We mainly focused on their importance in diagnosing GVHD incidence after liver transplantation.

RESULTS

A total of 18 articles reported 21 cases of GVHD after liver transplantation in pediatrics. Generally, there is a consensus on the advantage of HLA typing and chimerism analysis in confirming the diagnosis of GVHD after liver transplantation. However, there is an inconsistency in the timing and the application of the accurate HLA typing and chimerism analysis.

CONCLUSION

Further studies are required to assess the incidence of GVHD post-LT and to determine the impact of HLA typing and chimerism analysis in assessing the risk, early determination of GVHD incidence, and improving outcomes. This systematic review highlights the gap in the field of liver transplantation and calls for revisiting the guidelines to consider HLA typing and chimerism analysis in predicting GVHD before transplantation and diagnosing GVHD incidence after liver transplantation.