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The human leukocyte antigen (HLA) system plays a critical role in transplant immunology, influencing outcomes through various immune-mediated rejection mechanisms. Hyperacute rejection is driven by preformed donor-specific antibodies (DSAs) targeting HLAs, leading to complement activation and graft loss within hours to days. Acute rejection typically occurs within six months post-transplantation, involving cellular and humoral responses, including the formation of de novo DSAs. Chronic rejection, a key factor in long-term graft failure, often involves class II DSAs and complex interactions between the innate and adaptive immune systems. Advancements in HLA antibody detection, particularly single antigen bead (SAB) assays, have improved the sensitivity and characterization of DSAs. However, these assays face challenges like false positives from denatured antigens and false negatives due to low antibody titers or complement competition. Furthermore, molecular mismatch (MM) analysis has emerged as a potential tool for refining donor–recipient compatibility but faces some issues such as a lack of standardization. Highly sensitized patients with calculated panel-reactive antibodies (cPRA) of 100% face barriers to transplantation. Strategies like serum dilution, novel therapies (e.g., Imlifidase), and delisting approaches could refine immunological risk assessment and delisting strategies are essential to expand transplant opportunities for these patients. [ABSTRACT FROM AUTHOR]

Donor human leukocyte antigen (HLA)-specific antibodies (DSA) and non-HLA antibodies can cause allograft injury, possibly leading to chronic lung allograft dysfunction (CLAD) after lung transplantation. It remains unclear whether these antibodies are produced locally in the graft or derived solely from circulation. We hypothesized that DSA and non-HLA antibodies are produced in CLAD lungs. Lung tissue was prospectively collected from 15 CLAD patients undergoing retransplantation or autopsy. 0.3 g of fresh lung tissue was cultured for 4 days without or with lipopolysaccharide or CD40L: lung culture supernatant (LCS) was sampled. Protein eluate was obtained from 0.3 g of frozen lung tissue. The mean fluorescence intensity (MFI) of DSA and non-HLA antibodies was measured by Luminex and antigen microarray, respectively. LCS from all 4 patients who had serum DSA at lung isolation were positive for DSA, with higher levels measured after CD40L stimulation (CD40L+LCS). Of these, only 2 had detectable DSA in lung eluate. MFI of non-HLA antibodies from CD40L+LCS correlated with those from lung eluate but not with those from sera. Flow cytometry showed higher frequencies of activated lung B cells in patients whose CD40L+LCS was positive for DSA (n = 4) or high non-HLA antibodies (n = 6) compared to those with low local antibodies (n = 5). Immunofluorescence staining showed CLAD lung lymphoid aggregates with local antibodies contained larger numbers of IgG+ plasma cells and greater IL-21 expression. We show that DSA and non-HLA antibodies can be produced within activated B cell-rich lung allografts. [ABSTRACT FROM AUTHOR]

Antibody-mediated rejection (ABMR) is a significant obstacle to achieving optimal long-term outcomes after solid organ transplantation. The presence of donor-specific antibodies (DSAs), particularly against human leucocyte antigen (HLA), increases the risk of allograft rejection and subsequent graft loss. No effective treatment for ABMR currently exists, warranting novel approaches to target the HLA-specific humoral alloimmune response. Cellular therapies may hold promise to this end. According to publicly available sources as of now, three independent laboratories have genetically engineered a chimeric HLA antibody receptor (CHAR) and transduced it into human T cells, based on the demonstrated efficacy of chimeric antigen receptor T cell therapies in malignancies. These CHAR-T cells are designed to exclusively eliminate B cells that produce donor-specific HLA antibodies, which form the cornerstone of ABMR. CHAR technology generates potent and functional human cytotoxic T cells to target alloreactive HLA-specific B cells, sparing B cells with other specificities. Thus CHAR technology may be used as a selective desensitization protocol and to treat ABMR after solid organ transplantation. [ABSTRACT FROM AUTHOR]

Polyomavirus BK (BKPyV)-associated nephropathy (BKPyV-nephropathy) remains a significant cause of premature kidney allograft failure. In the absence of effective antiviral treatments, current therapeutic approaches rely on immunosuppression (IS) reduction, possibly at the risk of inducing alloimmunity. Therefore, we sought to explore the long-term effects of a tailored viro-immunologic surveillance and treatment program for BKPyV on the development of alloimmunity and kidney graft outcome. Forty-five pediatric kidney transplant recipients were longitudinally monitored for BKPyV replication, virus-specific immunity, and donor-specific HLA antibodies (DSAs). DNAemia developed in 15 patients who were treated with stepwise IS reduction. Among the other 30 patients, 17 developed DNAuria without DNAemia and 13 always resulted as BKPyV-negative. All patients with DNAemia cleared BKPyV after having mounted a virus-specific cellular immune response, and no biopsy-proven BKPyV-nephropathy was observed. The presence of cytotoxic populations directed to the BKPyV Large-T (LT) antigen early after transplantation protected kidney recipients from developing BKPyV replication, and the appearance of LT-specific T cells in viruric patients prevented the development of BKPyV-DNAemia. In our cohort, no significant correlation was observed between BKPyV-DNAemia and the development of DSA and antibody-mediated rejection. However, patients who experienced and cleared BKPyV-DNAemia had a worse allograft survival at a median follow-up of 18.9 years (p = 0.048). These data need to be confirmed in larger cohorts. [ABSTRACT FROM AUTHOR]

Induction therapy is a critical component of renal transplantation, aimed at reducing delayed graft function (DGF) and improving graft survival. This review assesses the impact of leading large national and international guidelines: National Institute for Health and Care Excellence (NICE), Kidney Disease: Improving Global Outcomes (KDIGO), and European Renal Best Practice (ERBP) propositions, focusing on their applicability to high-risk groups, specifically, on Black patients and those with donor-specific antibodies (DSAs). While NICE guidelines provide a standardized approach favoring basiliximab, concerns arise regarding their suitability for high-risk patients, who may benefit more from potent lymphocyte-depleting agents. KDIGO and ERBP guidelines advocate for personalized approaches, emphasizing genetic diversity and specific patient profiles to tailor immunosuppressive regimens effectively. This review advocates for a paradigm shift toward personalized induction therapy, integrating genetic insights to improve clinical outcomes and address health disparities. By tailoring induction therapies to the genetic and immunological profiles of transplant recipients, healthcare providers can enhance transplant success and ensure equitable healthcare for diverse populations. This approach underscores the importance of personalized medicine in achieving optimal outcomes in renal transplantation. This concern is of particular importance to Black individuals due to the specific genetic markers and health profiles relevant to this group, while recognizing the current gap in data regarding other ethnicities. [ABSTRACT FROM AUTHOR]

Antibody‐mediated rejection (AMR) in lung transplantation has been associated with poor long‐term clinical course and is a risk factor for chronic lung allograft dysfunction and graft loss. Appropriate management of AMR is necessary to improve graft survival in lung transplant recipients. There is currently no standardized approach to the treatment of lung AMR, and practices vary by institution. We sought to examine the efficacy of a standardized protocol of plasma exchange (PLEX) and IVIG in decreasing donor‐specific antibodies (DSAs) and improving AMR in lung transplant recipients. A retrospective chart review was conducted on all lung transplant recipients who completed a course of PLEX per UT Southwestern AMR protocol between January 2012 and December 2019 for diagnosis of AMR. Data were collected on the patient clinical course, treatment regimen, pre‐PLEX DSA, post‐PLEX DSA, follow‐up (> 1‐month post‐PLEX) DSA, and pre‐and post‐PLEX biopsy, when available. Of 527 patients who underwent lung transplantation during the study period, 56 (11%) received an acute course of PLEX every other day per protocol for AMR of lung transplant. Forty (71%) of 56 patients had one episode of AMR requiring PLEX; 16 patients (29%) had repeat episodes of AMR within 6 weeks to 47 months of the first episode. Most patients showed improvement in AMR on biopsy (69%) and a decline in DSA (68%). Our data suggest that treatment with combined PLEX and IVIG protocol appears effective for treating lung AMR. [ABSTRACT FROM AUTHOR]

Background: In kidney transplant recipients (KTR), BK polyomavirus-associated nephropathy (BKPyVAN) is a major cause of graft loss. To facilitate the clearance of BKPyV-DNAemia, reduction of immunosuppression is currently the treatment of choice but may increase the risk of graft rejection. Methods: This international CERTAIN study was designed to determine the risk of alloimmune response and graft dysfunction associated with immunosuppression reduction for BKPyV treatment in 195 pediatric KTR. Results: BKPyV-DNAemia was associated with a more than twofold increased risk of late T cell-mediated rejection (TCMR) (HR 2.22, p = 0.024), of de novo donor-specific HLA antibodies (dnDSA) and/or antibody-mediated rejection (ABMR) (HR 2.64, p = 0.002), and of graft function deterioration (HR 2.73, p = 0.001). Additional independent risk factors for dnDSA/ABMR development were a higher HLA mismatch (HR 2.72, p = 0.006) and re-transplantation (HR 6.40, p = 0.000). Other independent predictors of graft function deterioration were TCMR (HR 3.98, p = 0.003), higher donor age (HR 1.03, p = 0.020), and re-transplantation (HR 3.56, p = 0.013). Conclusions: These data indicate that reduction of immunosuppression for BKPyV-DNAemia management is associated with increased alloimmune response in pediatric KTR. Therefore, regular dnDSA screening and close monitoring of graft function in case of BKPyV-DNAemia followed by subsequent reduction of immunosuppressive therapy are recommended. Graphical sbstract: [ABSTRACT FROM AUTHOR]

Mesenchymal stromal cells (MSCs) have immunomodulatory properties and are therefore considered promising tools in kidney transplantation. Although most studies have been conducted with autologous MSCs, using allogeneic MSCs as an off-the-shelf product is more feasible in clinical settings. However, allogeneic MSCs could potentially induce an immune response, which might eventually be directed towards the kidney allograft because of shared human leukocyte antigen (HLA) epitope mismatches between the kidney and MSC donor. In this study, we performed in-depth analyses of two cohorts (n = 20) that received third-party MSC therapy after kidney transplantation. While the Neptune Study from Leiden University Medical Center specifically selected MSC to avoid repeated HLA antigen mismatches between kidney and MSC donors, the study from the University of Liège did not perform specific MSC selection. The comparative analyses of amino acid mismatches between these cohorts showed that MSC selection to avoid repeated HLA mismatches at the split antigen level was not sufficient to prevent repeated mismatches at the amino acid level. However, repeated amino acid mismatches were not associated with the occurrence of donor-specific antibodies (DSAs). Thus, the clinical relevance of repeated amino acid mismatches seems to be limited with regard to the risk of DSA formation. Since DSA formation was limited (3 of 20 patients) in this study, larger studies are required to investigate the relevance of preventing repeated HLA mismatches in allogeneic MSC therapy in kidney transplantation. [ABSTRACT FROM AUTHOR]

Chronic antibody-mediated rejection in kidney transplantation is a common cause of graft loss in the late post-transplant period. In this process, the role of the classical complement activation pathway is crucial due to the formation of immune complexes between donor-specific antibodies (DSAs) and donor antigens and the attachment of the C1q complement fragment. This study aimed to determine the levels of circulating C1q immunocomplexes (CIC-C1q) and complement activation (CH50), in sensitized kidney transplant recipients (KTRs). In this cross-sectional study we used serum samples from KTRs with de novo or preformed DSAs (n = 14), KTRs without DSAs (n = 28), and 22 subjects with no history of chronic kidney disease (controls). C1q immunocomplexes and CH50 concentration in serum were measured with the enzyme immunoassay (EIA) kit MicroVue CIC-C1q (Quidel, Athens, OH, USA) and EIA kit MicroVue CH50 (Quidel, OH, USA), respectively. Higher concentrations of CIC-C1q was observed in KTRs with DSAs in comparison with controls and with KTRs with no DSAs (6.8 ± 2.7 and 4.8 ± 1.9 vs. 5.0 ± 1.2 μg Eq/mL, respectively, p < 0.01). We found no difference in CIC-C1q between KTRs with no DSAs and controls. CIC-C1q levels were positively correlated with DSA titer. CH50 levels were decreased in KTRs with DSAs in comparison with controls and KTRs with no DSAs (39 ± 15 vs. 68 ± 40 and 71 ± 34 U Eq/mL, respectively, p < 0.01). There was no difference in CH50 between DSA-negative KTRs and controls. Kidney transplant recipients with DSAs had increased serum levels of C1q immunocomplexes and increased classical pathway complement activation. [ABSTRACT FROM AUTHOR]

Eplet mismatch has been recognized as a more precise strategy for determining HLA compatibility by analyzing donor-recipient HLA differences at the molecular level. However, predicting post-transplant alloimmunity using single-molecule eplet mismatch categories has not been validated in Asian cohorts. We examined a cohort of Southeast Asian kidney transplant recipients (n = 234) to evaluate HLA-DR/DQ eplet mismatch as a predictor of de novo donor-specific antibody (dnDSA) development. HLA-DR/DQ single-molecule eplet mismatch was quantified using HLA Matchmaker, and we utilized previously published HLADR/DQ eplet mismatch thresholds to categorize recipients into alloimmune risk groups and evaluate their association with dnDSA development. Recognizing that the predominance of cyclosporine use (71%) may alter published eplet mismatch thresholds derived from a largely tacrolimus-based (87%) cohort, we evaluated cohort-specific thresholds for HLA-DR/DQ single-molecule eplet mismatch categories. Recipient ethnicities included Chinese (65%), Malays (17%), Indians (14%), and others (4%). HLA-DR/DQ dnDSA developed in 29/234 (12%) recipients after a median follow-up of 5.4 years, including against isolated HLA-DR (n = 7), isolated HLA-DQ (n = 11), or both (n = 11). HLA-DR/DQ single-molecule eplet mismatch risk categories correlated with dnDSA-free survival (p = 0.001) with low-risk recipients having a dnDSA prevalence of 1% over 5 years. The cohortspecific alloimmune risk categories improved correlation with HLA-DR/DQ dnDSA-free survival and remained significant after adjusting for calcineurin inhibitor and anti-metabolite immunosuppression (p < 0.001). We validated the performance of single-molecule eplet mismatch categories as a prognostic biomarker for HLA-DR/DQ dnDSA development in a cohort of predominantly Asian kidney transplant recipients after adjusting for different immunosuppression regimens. [ABSTRACT FROM AUTHOR]

Introduction: Donor-specific antibodies (DSAs) correspond to anti-HLA antibodies of the recipient that are specifically directed to a mismatched antigen of the donor. In the setting of solid organ transplantation DSAs are associated with rejection. Their role is still debated in allogeneic cell transplantation. International guidelines recommend testing patients for DSA before transplant, and if possible, choosing a donor with negative screening. Methods: We collected clinical data of 236 recipients of alloSCT, performed at our institution from March 2019 to October 2023, to evaluate their impact on engraftment. Serum from all patients was tested for DSA. Results: 186 patients (79%) achieved sustained myeloid engraftment within day 30 post alloSCT. Thirty-two out 236 (13%) patients engrafted after day 30 post alloSCT. The median times to neutrophil engraftment and platelet engraftment were respectively 21 days (range 11-121 days) and 19 days (range 10-203 days). Fourteen out 236 patients (6%) experienced PrGF. .Twenty-nine patients (12 %) were DSA-positive. Among 29 patients with DSA positivity, 17 had a haploidentical donor and 12 had a UD donor. DSA positivity directly correlates respectively with neutrophil and platelets engraftment failure at 30 days after alloSCT (p=0.01 and p= 0.0004). Univariate Cox analysis showed that factors, including DSAs positivity, disease type, disease status, donor type, conditioning regimen, patient's age, and CD34+ were correlated with neutrophil and platelet engraftment failure at 30 days after alloSCT. Younger patients with DSA negativity, with acute leukemia, in complete response at the time of transplant, who received a higher dose of CD34+ cells from a sibling donor after a myeloablative conditioning regimen, have a reduced risk of neutrophil and platelet engraftment failure at day +30 post alloSCT.Multivariate analysis confirmed the impact of the presence of DSA only for platelet engraftment, confirming the role of type and status disease, donor type, recipient age, and CD34+ cells infused on engraftment. DSA presence has no impact on TRM, DFS, and OS. Discussion: PrGF has a multifactorial pathogenesis, where DSA is not the only player, but its impact could vary depending on the transplant platform. Thus patient screening may be helpful to choose the best donor and transplant strategy. [ABSTRACT FROM AUTHOR]

The functional outcomes and restoration of form after vascularized composite allotransplantation (VCA) have exceeded the results that could be achieved with current autologous surgical techniques. However, the longevity of VCA grafts has been limited due to the development of donor-specific antibodies (DSAs), and chronic rejection and graft failure occur despite long-term immunotherapy. Furthermore, despite widespread consensus that these non-life-saving transplants are beneficial for select patients, the application of VCA is limited by the need for lifelong immunosuppression. Therefore, attempts to achieve drug-free tolerance through safe and effective therapies are critical. This review highlights recent publications regarding alloantibody-mediated rejection (AMR) in various VCAs with a focus on the critical need for novel tolerance-inducing strategies. The development and implementation of effective methods of inducing tolerance, such as the use of anti-CD3 immunotoxins, could drastically improve VCA graft outcomes and recipient quality of life. [ABSTRACT FROM AUTHOR]

Calculated PRA testing in kidney transplantation has revolutionized the field by enabling a more accurate assessment of compatibility and risk prediction for AMR. On the other hand, The PIRCHE algorithm aims to identify the potentially immunogenic human leukocyte antigens (HLA) epitopes on the donor graft that are recognized by the recipient's HLA antibodies.

The functional outcomes and restoration of form after vascularized composite allotransplantation (VCA) have exceeded the results that could be achieved with current autologous surgical techniques. However, the longevity of VCA grafts has been limited due to the development of donor-specific antibodies (DSAs), and chronic rejection and graft failure occur despite long-term immunotherapy. Furthermore, despite widespread consensus that these non-life-saving transplants are beneficial for select patients, the application of VCA is limited by the need for lifelong immunosuppression. Therefore, attempts to achieve drug-free tolerance through safe and effective therapies are critical. This review highlights recent publications regarding alloantibody-mediated rejection (AMR) in various VCAs with a focus on the critical need for novel tolerance-inducing strategies. The development and implementation of effective methods of inducing tolerance, such as the use of anti-CD3 immunotoxins, could drastically improve VCA graft outcomes and recipient quality of life.

The use of posttransplant cyclophosphamide has revolutionized the field of haploidentical hematopoietic stem cell transplant. The impact has been especially enhanced in low- and middle-income countries. Unrelated donor pool in developing nations is often limited due to the lack of large unrelated donor registries. Donor-specific antibodies (DSAs) are preformed immunoglobulin G anti-human leukocyte antigen (HLA) antibodies against HLA antigens that are not shared with the donor. We present successful desensitization in a 13-year-old patient with class III β-thalassemia with very high MFI DSAs with flow crossmatch positivity, persisting after pretransplant immunosuppression.

Introduction: Uterus transplantation (UTx) is a novel treatment for absolute uterine infertility. Acute T cell–mediated rejection (TCMR) can be monitored only through serial cervical biopsies. Methods: This study, the first of its kind in human transplantation, evaluated clinical, serological, and pathophysiological manifestations of allograft rejection from immunosuppression withdrawal (ISW) to graft hysterectomy (Hx). Results: Following live birth, immunosuppression was abruptly withdrawn from six living‐donor UTx recipients. ISW occurred at a median of 7.4 weeks before graft Hx. Post‐ISW signs of rejection included: (1) discoloration of the cervix; (2) increased uterine size compared to day of ISW; (3) serological evidence of eosinophilia and progressive development of donor‐specific antibodies (DSA) or child‐specific antibodies (CSA); (4) histopathological evidence of TCMR in cervical biopsies preceding the development of antibodies in serum; and (5) C4d deposition in tissue before formation of DSA or CSA in all but two recipients. At graft Hx, endometrial glands were preferentially targeted for destruction over stroma while parametrial arteries displayed variable arteritis and fibrointimal hyperplasia. Conclusion: Recognition of the progression of uterine allograft rejection may be important for other human organ recipients and drive research on modulation of immunosuppression and the paradoxical relationship between adaptive cellular and humoral immunity in natural pregnancies. Trial Registration: ClinicalTrials.gov identifier: NCT02656550 [ABSTRACT FROM AUTHOR]

Mesenchymal stromal cells (MSCs) have immunomodulatory properties and are therefore considered promising tools in kidney transplantation. Although most studies have been conducted with autologous MSCs, using allogeneic MSCs as an off-the-shelf product is more feasible in clinical settings. However, allogeneic MSCs could potentially induce an immune response, which might eventually be directed towards the kidney allograft because of shared human leukocyte antigen (HLA) epitope mismatches between the kidney and MSC donor. In this study, we performed in-depth analyses of two cohorts (n = 20) that received third-party MSC therapy after kidney transplantation. While the Neptune Study from Leiden University Medical Center specifically selected MSC to avoid repeated HLA antigen mismatches between kidney and MSC donors, the study from the University of Liège did not perform specific MSC selection. The comparative analyses of amino acid mismatches between these cohorts showed that MSC selection to avoid repeated HLA mismatches at the split antigen level was not sufficient to prevent repeated mismatches at the amino acid level. However, repeated amino acid mismatches were not associated with the occurrence of donor-specific antibodies (DSAs). Thus, the clinical relevance of repeated amino acid mismatches seems to be limited with regard to the risk of DSA formation. Since DSA formation was limited (3 of 20 patients) in this study, larger studies are required to investigate the relevance of preventing repeated HLA mismatches in allogeneic MSC therapy in kidney transplantation.

Polyomavirus BK (BKPyV)-associated nephropathy (BKPyV-nephropathy) remains a significant cause of premature kidney allograft failure. In the absence of effective antiviral treatments, current therapeutic approaches rely on immunosuppression (IS) reduction, possibly at the risk of inducing alloimmunity. Therefore, we sought to explore the long-term effects of a tailored viro-immunologic surveillance and treatment program for BKPyV on the development of alloimmunity and kidney graft outcome. Forty-five pediatric kidney transplant recipients were longitudinally monitored for BKPyV replication, virus-specific immunity, and donor-specific HLA antibodies (DSAs). DNAemia developed in 15 patients who were treated with stepwise IS reduction. Among the other 30 patients, 17 developed DNAuria without DNAemia and 13 always resulted as BKPyV-negative. All patients with DNAemia cleared BKPyV after having mounted a virus-specific cellular immune response, and no biopsy-proven BKPyV-nephropathy was observed. The presence of cytotoxic populations directed to the BKPyV Large-T (LT) antigen early after transplantation protected kidney recipients from developing BKPyV replication, and the appearance of LT-specific T cells in viruric patients prevented the development of BKPyV-DNAemia. In our cohort, no significant correlation was observed between BKPyV-DNAemia and the development of DSA and antibody-mediated rejection. However, patients who experienced and cleared BKPyV-DNAemia had a worse allograft survival at a median follow-up of 18.9 years (p = 0.048). These data need to be confirmed in larger cohorts.

The use of posttransplant cyclophosphamide has revolutionized the field of haploidentical hematopoietic stem cell transplant. The impact has been especially enhanced in low‑ and middle‑income countries. Unrelated donor pool in developing nations is often limited due to the lack of large unrelated donor registries. Donor‑specific antibodies (DSAs) are preformed immunoglobulin G anti‑human leukocyte antigen (HLA) antibodies against HLA antigens that are not shared with the donor. We present successful desensitization in a 13‑year‑old patient with classIII β‑thalassemia with very high MFI DSAs with flow crossmatch positivity, persisting after pretransplant immunosuppression. [ABSTRACT FROM AUTHOR]

IntroductionDonor-specific antibodies (DSAs) correspond to anti-HLA antibodies of the recipient that are specifically directed to a mismatched antigen of the donor. In the setting of solid organ transplantation DSAs are associated with rejection. Their role is still debated in allogeneic cell transplantation. International guidelines recommend testing patients for DSA before transplant, and if possible, choosing a donor with negative screening.MethodsWe collected clinical data of 236 recipients of alloSCT, performed at our institution from March 2019 to October 2023, to evaluate their impact on engraftment. Serum from all patients was tested for DSA.Results186 patients (79%) achieved sustained myeloid engraftment within day 30 post alloSCT. Thirty-two out 236 (13%) patients engrafted after day 30 post alloSCT. The median times to neutrophil engraftment and platelet engraftment were respectively 21 days (range 11-121 days) and 19 days (range 10-203 days). Fourteen out 236 patients (6%) experienced PrGF. .Twenty-nine patients (12 %) were DSA-positive. Among 29 patients with DSA positivity, 17 had a haploidentical donor and 12 had a UD donor. DSA positivity directly correlates respectively with neutrophil and platelets engraftment failure at 30 days after alloSCT (p=0.01 and p= 0.0004). Univariate Cox analysis showed that factors, including DSAs positivity, disease type, disease status, donor type, conditioning regimen, patient's age, and CD34+ were correlated with neutrophil and platelet engraftment failure at 30 days after alloSCT. Younger patients with DSA negativity, with acute leukemia, in complete response at the time of transplant, who received a higher dose of CD34+ cells from a sibling donor after a myeloablative conditioning regimen, have a reduced risk of neutrophil and platelet engraftment failure at day +30 post alloSCT.Multivariate analysis confirmed the impact of the presence of DSA only for platelet engraftment, confirming the role of type and status disease, donor type, recipient age, and CD34+ cells infused on engraftment. DSA presence has no impact on TRM, DFS, and OS.DiscussionPrGF has a multifactorial pathogenesis, where DSA is not the only player, but its impact could vary depending on the transplant platform. Thus patient screening may be helpful to choose the best donor and transplant strategy.

Eplet mismatch has been recognized as a more precise strategy for determining HLA compatibility by analyzing donor-recipient HLA differences at the molecular level. However, predicting post-transplant alloimmunity using single-molecule eplet mismatch categories has not been validated in Asian cohorts. We examined a cohort of Southeast Asian kidney transplant recipients (n = 234) to evaluate HLA-DR/DQ eplet mismatch as a predictor of de novo donor-specific antibody (dnDSA) development. HLA-DR/DQ single-molecule eplet mismatch was quantified using HLA Matchmaker, and we utilized previously published HLA-DR/DQ eplet mismatch thresholds to categorize recipients into alloimmune risk groups and evaluate their association with dnDSA development. Recognizing that the predominance of cyclosporine use (71%) may alter published eplet mismatch thresholds derived from a largely tacrolimus-based (87%) cohort, we evaluated cohort-specific thresholds for HLA-DR/DQ single-molecule eplet mismatch categories. Recipient ethnicities included Chinese (65%), Malays (17%), Indians (14%), and others (4%). HLA-DR/DQ dnDSA developed in 29/234 (12%) recipients after a median follow-up of 5.4 years, including against isolated HLA-DR (n = 7), isolated HLA-DQ (n = 11), or both (n = 11). HLA-DR/DQ single-molecule eplet mismatch risk categories correlated with dnDSA-free survival (p = 0.001) with low-risk recipients having a dnDSA prevalence of 1% over 5 years. The cohort-specific alloimmune risk categories improved correlation with HLA-DR/DQ dnDSA-free survival and remained significant after adjusting for calcineurin inhibitor and anti-metabolite immunosuppression (p < 0.001). We validated the performance of single-molecule eplet mismatch categories as a prognostic biomarker for HLA-DR/DQ dnDSA development in a cohort of predominantly Asian kidney transplant recipients after adjusting for different immunosuppression regimens.

The main reason for graft loss is the rejection of the donor organ, which may occur at different time after transplantation and may be caused by the recipient’s organism reaction against donor’s human leukocyte antigen (HLA) proteins. Donor-specific antibodies (DSA) are produced in patient’s organism as a response to foreign HLA antigens. Aim. The purpose of our study was to evaluate the effects of already existed and/or de novo generated DSAs in liver transplantation as predictors of graft rejection and to establish an interconnection between blood biochemical parameters (Alanine aminotransferase (ALT), aspartate aminotransferase (AST), total bilirubin level) with the level of DSA in patients with liver transplant. Methods. xMAP-Luminex next generation flow cytometry technology and LABScreen Single antigen beads reagent (Onelambda, USA) were used for antiHLA determination. Total bilirubin level was detected photometrically. The activity of ALT and AST was determined spectrophotometrically on the automatic analyzer COBAS C 111 (Roche, Switzerland) in accordance with the manufacture’s instruction. Results. Detection of DSA and PRA was important at the same level as measurement of classical biochemical parameters of liver function (ALT, AST etc.) for monitoring of graft status and prevention of acute or chronical rejection and choosing correct immunosuppression protocol. Conclusions. The DSA and PRA levels as well as total bilirubin and ALT and AST activity corresponded to each other and could be used for comprehensive both pre- and post-transplantation screening of patients requiring liver transplantation or re-transplantation. Detection of DSA and PRA was important at the same level as measurement of classical biochemical parameters of liver function (ALT, AST etc.) for monitoring of graft status and prevention of acute or chronical rejection and choosing correct immunosuppression protocol.

Anti-human leukocyte antigen (HLA) donor-specific antibodies (DSAs) are associated with antibody-mediated rejection and chronic allograft nephropathy in kidney transplantation. The interpretation of immunological assays for DSAs can be challenging due to discordant results. In this report, we present two cases of kidney transplantation involving patients with anti-HLA-C DSAs. We discuss the interpretation of their immunological tests, including complement-dependent cytotoxicity (CDC) crossmatches, flow cytometry crossmatches, and donor-specific antigen using single-antigen bead (SAB) assays, which influenced therapeutic decisions. In the first case, the patient exhibited isolated B-cell-positive crossmatch and autoantibodies, prompting the consideration of polyclonal autoantibodies in the context of underlying hepatitis C infection. The SAB assay detected only one DSA against HLA-C 03:03:01 (mean fluorescence intensity – 27,127). After careful evaluation and confirmation of negative CDC crossmatch, transplantation proceeded, and the patient demonstrated good graft function. In the second case, the patient showed a positive T-cell crossmatch along with anti-Class I HLA DSAs against HLA C*07:01 and HLA C*07:02. Despite these findings, transplantation was performed based on the absence of complement-binding antibodies. The patient experienced good graft recovery with stable kidney function. The presence of HLA-C DSAs poses challenges in transplantation decision-making. Despite conflicting studies, the pathological nature of these antibodies has been demonstrated. Careful interpretation of immunological tests and consideration of the overall clinical context are essential in making therapeutic decisions. Further research is needed to understand the clinical significance of HLA-C DSAs and their impact on graft outcomes.

Background: The study purpose was to add to limited literature assessing anti‐HLA donor‐specific antibody (DSA) appearance, clearance, specificity, and impact in intestinal/multivisceral (MV) transplant as well as the value of serial monitoring following an institutional protocol shift implementing serial monitoring. Methods: This single‐center retrospective review included intestinal/MV recipients transplanted 1/1/15–9/31/17 with completed DSA testing. Patients were divided into groups based on DSA presence post‐transplant. The primary outcome was biopsy‐proven acute rejection (BPAR). Secondary outcomes included graft loss and death. Descriptive analysis of DSA was completed. Results: Of the 35 intestinal/MV recipients (60% pediatric) with DSA testing, 24 patients had post‐transplant DSA. Fifteen patients in the DSA(+) group had T‐cell‐mediated BPAR versus five in the DSA(−) group (63% vs 45%, p =.47). Days to BPAR were 25 [IQR 19–165] (DSA(+) group) versus 232 [IQR 25.5–632.5] (DSA(−) group) (p =.066). There were no differences between groups for graft loss or death. One hundred and five DSA were identified in the DSA(+) group with 63% being class II, and 54% cleared during follow‐up. DSA were directed against 50 different HLA alleles, with the most common being directed against HLA‐ DQ (35%). Time to first DSA and to clearance did not differ between class I and II. Conclusion: Findings confirm previous data that suggest post‐transplant DSA in this population may lead to increased BPAR or shorter time to BPAR, although not statistically significant. Most DSA were identified within the first month after transplant, and ahead of rejection identification on biopsy. DSA therefore may have utility as an early rejection biomarker and use may be considered in place of early protocol biopsies, particularly in pediatric patients. We identified novel findings of DSA directed against a large breadth of HLA in intestinal/MV patients. [ABSTRACT FROM AUTHOR]

T‐cell mediated rejection (TCMR), de novo anti‐HLA donor‐specific antibodies (dnDSAs) and ensuing antibody‐mediated rejection (ABMR) reduce kidney transplantation (KT) survival. The immunomodulatory effects of 25‐hydroxyvitamin D [25(OH)D] could be beneficial for KT outcomes. We aimed to evaluating the association between 25(OH)D levels, the development of dnDSAs, clinical TCMR and ABMR, and graft survival. This single center retrospective study included 253 KT recipients (KTRs) transplanted without preformed DSA between 2010 and 2013. We measured 25(OH)D in successive serum samples: at KT (M0) and M12 for the entire cohort, and additionally at M24 and/or M36 when sera were available. We assessed graft outcomes up to 5 years post‐KT. The proportion of KTRs having sufficient 25(OH)D at KT (M0) was high (81.4%) and then dropped at M12 (71.1%). KTRs with sufficient 25(OH)D at M0 experienced less clinical TCMR (HR, 0.41; 95% CI, 0.19–0.88 in multivariate analysis). A sufficient 25(OH)D at M12 was independently associated with a longer dnDSA‐free survival (HR, 0.34; 95% CI, 0.17–0.69). There was no association between 25(OH)D and clinical AMBR. Studying the KTRs with 25(OH)D measurements at M12, M24 and M36 (n = 203), we showed that 25(OH)D sufficiency over the 3 first‐years post‐KT was associated with a longer graft survival in multivariate analyses (HR, 0.39; 95% CI, 0.22–0.70). To our knowledge, this study is the first showing an association between 25(OH)D sufficiency post‐KT and dnDSA occurrence in KTRs. Moreover, we reinforce previously published data showing an association between 25(OH)D, TCMR and graft survival in KT. [ABSTRACT FROM AUTHOR]

Donor-specific antibodies (DSAs) are essential causes of graft rejection in haploidentical hematopoietic stem cell transplantation (haplo-HSCT). DSAs are unavoidable for some patients who have no alternative donor. Effective interventions to reduce DSAs are still needed, and the cost of the current therapies is relatively high. In this study, we retrospectively analyzed the data of 11 DSA-positive patients who received haplo-HSCT at our center and evaluated the therapeutic efficacy of the combination of intravenous immunoglobulin (IVIG), dexamethasone and high dose of transfused mononuclear cells (MNCs) for DSA desensitization. The kinetics of DSAs at different times and the engraftment and transplantation outcomes were also observed. We found that all patients had successful donor-cell engraftment and that no patient developed poor graft function. The median engraftment times of neutrophils and platelets were 14 days (range, 11–24 days) and 13 days (range, 11–123 days), respectively. The DSA levels of all patients became negative or dropped under 2000 within 22 days after HSCT. A total of 36.4% of patients developed grade II–IV acute graft-versus-host disease (aGVHD), and 9.1% of patients died of severe gastrointestinal aGVHD. Of the 7 surviving patients, four were diagnosed with chronic GVHD. After a median follow-up of 28.9 months (2.0–52.1 months), four patients died: of relapse (two), aGVHD (one), and multiple-organ failure (one). The 2-year OS, DFS, and NRM were 63.6%, 45.4%, and 18.2%, respectively. Combination therapy with IVIG, dexamethasone, and a high dose of MNCs transfusion, a simple and efficient procedure, was safe and effective for DSA desensitization and peripheral blood stem cell (PBSC) engraftment. [ABSTRACT FROM AUTHOR]

Two semi-quantitative, Luminex-based, single-antigen bead (SAB) assays are available to detect anti-HLA antibodies and evaluate their reactivity with complement binding. Sera from 97 patients with positive panel reactive antibody tests (>5%) were analyzed with two SAB tests, Immucor (IC) and One-Lambda (OL), for anti-HLA antibody detection and the evaluation of their complement-binding capacity. IC detected 1608/8148 (mean fluorescent intensity (MFI) 4195 (1995–11,272)) and 1136/7275 (MFI 6706 (2647–13,184)) positive anti-HLA class I and II specificities, respectively. Accordingly, OL detected 1942/8148 (MFI 6185 (2855–12,099)) and 1247/7275 (MFI 9498 (3630–17,702)) positive anti-HLA class I and II specificities, respectively. For the IC assay, 428/1608 (MFI 13,900 (9540–17,999)) and 409/1136 (MFI 11,832 (7128–16,531)) positive class I and II specificities bound C3d, respectively. Similarly, OL detected 485/1942 (MFI 15,452 (9369–23,095)) and 298/1247 (MFI18,852 (14,415–24,707)) C1q-binding class I and II specificities. OL was more sensitive in detecting class I and II anti-HLA antibodies than IC was, although there was no significant difference in the number of class II specificities per case. MFI was higher for complement vs. non-complement-binding anti-HLA antibodies in both assays. Both methods were equal in detecting complement-binding anti-HLA class I antibodies, whereas the C3d assay was more sensitive in detecting complement-binding anti-HLA class II antibodies. [ABSTRACT FROM AUTHOR]

Given the risk of rejection, the presence of preformed donor specific antibodies (DSA) contraindicates transplantation in most allocation systems. However, HLA-Cw and -DP DSA escape this censorship. We performed a multicentric observational study, in which the objective was to determinate risk factors of acute antibody-mediated rejection (aABMR) in recipients transplanted with preformed isolated Cw- or DP-DSA. Between 2010 and 2019, 183 patients were transplanted with a preformed isolated Cw- or DP-DSA (92 Cw-DSA; 91 DP-DSA). At 2 years, the incidence of aABMR was 12% in the Cw-DSA group, versus 28% in the DP-DSA group. Using multivariable Cox regression model, the presence of a preformed DP-DSA was associated with an increased risk of aABMR (HR = 2.32 [1.21-4.45 (p = 0.001)]) compared with Cw-DSA. We also observed a significant association between the DSA's MFI on the day of transplant and the risk of aABMR (HR = 1.09 [1.08-1.18], p = 0.032), whatever the DSA was. Interaction term analysis found an increased risk of aABMR in the DP-DSA group compared with Cw-DSA, but only for MFI below 3,000. These results may plead for taking these antibodies into account in the allocation algorithms, in the same way as other DSA. [ABSTRACT FROM AUTHOR]

Human leucocyte antigen (HLA) alleles may generate antibodies that are undetectable by routine single‐antigen beads (SABs) assays if their unique epitopes are unrepresented. We aimed to describe the prevalence and explore the potential impact of unrepresented HLA alleles in standard SAB kits in our cohort. All individuals who had undergone two‐field HLA typing (HLA‐A/B/C/DRB1/DQA1/‐DQB1/‐DPA1/‐DPB1) from February 2021 to July 2023 were included. Two‐field HLA‐DRB3/4/5 typing was imputed. Each unrepresented allele was compared with the most similar represented allele in the standard LABScreen, LABScreen ExPlex (One Lambda) and the LIFECODES (Immucor) SAB kits. Differences in eplet expression (HLA Eplet Registry) were identified. Differences in three‐dimensional molecular structures were visualized using generated models (SWISS‐MODEL). Two‐field HLA typing was performed for 116 individuals. Overall, 16.7% of all HLA alleles, found in 36.2% of individuals, were unrepresented by all SAB test kits. Four eplets, found in 12.9% of individuals, were unrepresented in at least 1 SAB kit. Non‐Chinese individuals were more likely to have unrepresented HLA alleles and eplets than Chinese individuals. There were differences in HLA allele and eplet representation amongst the different SAB test kits. Use of supplementary SAB test kits may improve HLA allele and eplet representation. Although some HLA alleles were unrepresented, most epitopes were represented in current SAB kits. However, some unrepresented alleles may contain epitopes which may generate undetectable antibodies. Further studies may be needed to investigate the potential clinical impact of these unrepresented alleles and eplets, especially in certain ethnic populations or at‐risk individuals. [ABSTRACT FROM AUTHOR]

Lung transplantation. like other transplants, carries a risk of graft rejection due to genetic differences between the donor and the recipient. In this paper, we focus on antibody-mediated rejection, which can cause acute and more importantly chronic graft dysfunction and subsequently shortened allograft survival. We present the case of a 46-year-old patient who, two months after lung transplantation (LTx), developed AMR manifested by the deterioration of graft function and de novo production of donor-specific antibodies (DSA): DQ3 (DQ7, DQ8. DQ9). As the patient was after left single LTx and heavily oxygen dependent a transbronchial biopsy was deemed to be high risk and it was decided to determine the clinical significance of the detected antibodies by their ability to bind complement. The test confirmed that the detected DSAs have the ability cause cytotoxicity of the transplanted organ. After treatment with methotrexate, intravenous immunoglobulin G (IVIg) and alemtuzumab, the patient's condition improved and a complete decrease in DSA was obtained. However, after a year, the production of antibodies increased sharply. Treatment with IVIg, cyclophosphamide and plasmapheresis slightly improved the patient's condition, reducing the MFI DSA values by half, but leaving them at high levels. Based on this clinical case, we discuss problems with making a diagnosis, choosing the right AMR treatment and monitoring the patient's condition during treatment. We also indicate a poor prognosis in the case of the production of DSA antibodies at tlie DQ locus. [ABSTRACT FROM AUTHOR]

The presence in a recipient of antibodies directed against donor-specific antigens represents a major obstacle to transplantation. Removal of these antibodies represents a challenge for physicians dealing with kidney transplantation. Several strategies, techniques, and old and new drugs are currently used for desensitizing these patients. Desensitization may either occur before transplantation, at the time of transplantation, or after transplantation according to whether physicians are dealing with living or deceased donors. Different techniques may be used to reveal the presence of antibodies in the recipients; each technique has different sensitivities and specificities, and different advantages and drawbacks. The targets of the drugs used to desensitize are B cells, plasma cells, the antibodies themselves, and, finally, the complement that is the final actor causing tissue disruption. B cells are relatively easy to target; targeting the plasma cell is more difficult. Indeed, several new drugs are also used in randomized trials to defeat plasma cells. Antibodies may be removed easily, but their removal is often followed by antibody rebound. The complement is not easy to defeat and new drugs are currently used for this aim. Overall, despite difficulties, desensitization is currently possible in many cases, to obtain a safe and successful transplantation.

Background: We have performed a retrospective analysis of anti-HLA class I MHC and class II MHC antibodies measured using a single antigen bead (SAB) assay and a panel reactive antibody (PRA) assay. Material and methods: A group of 256 patients with end-stage renal disease (ESRD) was tested for anti-HLA antibodies in the tissue typing laboratory between 2017 and 2020. In the cohort, the serum samples of patients waiting for transplantation were tested. Both the PRA and SAB tests of these patients were analyzed using the Luminex (Immucor) method. The threshold of positivity was accepted as median fluorescence intensities (MFI) ≥1000 for PRA screening and MFI ≥750 for SAB screening. Results: Overall, antibodies to HLA antigens were detected in 202 (78.9%) out of 256 patients in the PRA study. Antibodies against both class I/II antigens were detected only in 15.6% of these patients, whereas antibodies against only against class I HLA in 31.3% and only against class II HLA in 32.0%. By comparison, the SAB study found that 66.8% of patients were positive for HLA antigens. Furthermore, donor-specific antibodies (DSA) were detected in 52.0% of PRA-positive patients and 52.6% of SAB-positive patients. It was shown that 168 patients (83.2%) out of 202 PRA-positive patients were found to be SAB-positive. In addition, 51 patients negative in the SAB assay (94.4%) were also negative in the PRA assay. Statistical analysis established a significant correlation between the PRA and SAB positivity (p > 0.001). It was also shown that MFI ≥3000 PRA positivity for class I HLA antigens (p = 0.049) and MFI ≥5000 PRA positivity for class II antigens (p < 0.001) correlated with the SAB positivity in patients. Conclusion: Our results showed the importance of both PRA and SAB assays to define the status of sensitization in patients. [ABSTRACT FROM AUTHOR]

The presence of donor‐specific antibodies (DSA), mainly against HLA, increases the risk of allograft rejection. Moreover, antibody‐mediated rejection (ABMR) remains an important barrier to optimal long‐term outcomes after solid organ transplantation. The development of chimeric autoantibody receptor T lymphocytes has been postulated for targeted therapy of autoimmune diseases. We aimed to develop a targeted therapy for DSA desensitization and ABMR, generating T cells with a chimeric HLA antibody receptor (CHAR) that specifically eliminates DSA‐producing B cells. We have genetically engineered an HLA‐A2‐specific CHAR (A2‐CHAR) and transduced it into human T cells. Then, we have performed in vitro experiments such as cytokine measurement, effector cell activation, and cytotoxicity against anti‐HLA‐A2 antibody‐expressing target cells. In addition, we have performed A2‐CHAR‐Tc cytotoxic assays in an immunodeficient mouse model. A2‐CHAR expressing T cells could selectively eliminate HLA‐A2 antibody‐producing B cells in vitro. The cytotoxic capacity of A2‐CHAR expressing T cells mainly depended on Granzyme B release. In the NSG mouse model, A2‐CHAR‐T cells could identify and eradicate HLA‐A2 antibody‐producing B cells even when those cells are localized in the bone marrow. This ability is effector:target ratio dependent. CHAR technology generates potent and functional human cytotoxic T cells to target alloreactive HLA class I antibody‐producing B cells. Thus, we consider that CHAR technology may be used as a selective desensitization protocol or an ABMR therapy in transplantation. [ABSTRACT FROM AUTHOR]

Allosensitization represents a major barrier to heart transplantation. We previously reported favorable 1-year outcomes of complement inhibition at transplant in highly sensitized recipients. We now report a longer follow-up. In this single-arm trial (NCT02013037), 20 patients with panel reactive antibodies ≥70% and preformed donor-specific antibodies received eculizumab during the first 2 months post-transplant. The primary end-point was antibody-mediated rejection ≥ pAMR2 and/or left ventricular dysfunction. The median follow-up was 4.8 years. Beyond the first year post-transplant, there were no episodes of pAMR2 or greater and no Left Ventricular (LV) dysfunction. There were 3 deaths, 1 episode of pAMR1, and 1 patient with minimal de novo cardiac allograft vasculopathy. Compared to a matched control group, we observed a nonstatistically significant benefit of eculizumab with a lower incidence of the primary end-point or death (primary end-point: hazard ratio = 0.50, 95% confidence interval = 0.15-1.67, and p = 0.26; mortality: hazard ratio = 0.51, 95% confidence interval = 0.13-2.07, and p = 0.35). Our results support the utility of complement inhibition for high-immunological-risk recipients. ClinincalTrials.gov, NCT02013037. https://clinicaltrials.gov/ct2/show/NCT02013037?term=eculizumab&cond=heart+transplantation&draw=2&rank=1 [ABSTRACT FROM AUTHOR]

Tocilizumab (TCZ), an IL-6 inhibitor, has shown promise in the treatment of donor-specific antibodies (DSA) and chronic antibody-mediated rejection (AMR) in renal transplant recipients. However, its use in lung transplantation has not been described. This retrospective case–control study compared AMR treatments containing TCZ in 9 bilateral lung transplant recipients to 18 patients treated for AMR without TCZ. Treatment with TCZ resulted in more clearance of DSA, lower recurrence of DSA, lower incidence of new DSA, and lower rates of graft failure when compared to those treated for AMR without TCZ. The incidence of infusion reactions, elevation in transaminases, and infections were similar between the 2 groups. These data support a role for TCZ in pulmonary AMR and establish preliminary evidence to design a randomized controlled trial of IL-6 inhibition for the management of AMR. [ABSTRACT FROM AUTHOR]

The presence in a recipient of antibodies directed against donor-specific antigens represents a major obstacle to transplantation. Removal of these antibodies represents a challenge for physicians dealing with kidney transplantation. Several strategies, techniques, and old and new drugs are currently used for desensitizing these patients. Desensitization may either occur before transplantation, at the time of transplantation, or after transplantation according to whether physicians are dealing with living or deceased donors. Different techniques may be used to reveal the presence of antibodies in the recipients; each technique has different sensitivities and specificities, and different advantages and drawbacks. The targets of the drugs used to desensitize are B cells, plasma cells, the antibodies themselves, and, finally, the complement that is the final actor causing tissue disruption. B cells are relatively easy to target; targeting the plasma cell is more difficult. Indeed, several new drugs are also used in randomized trials to defeat plasma cells. Antibodies may be removed easily, but their removal is often followed by antibody rebound. The complement is not easy to defeat and new drugs are currently used for this aim. Overall, despite difficulties, desensitization is currently possible in many cases, to obtain a safe and successful transplantation. [ABSTRACT FROM AUTHOR]

The presence of preformed cytotoxic donor-specific antibodies (DSAs) has been associated with inferior allograft outcomes in the immediate posttransplant period. Since the 1970s, the primary method for determining the presence of DSAs has been the complement-dependent cytotoxicity crossmatch. Solid phase assays on the Luminex platform were introduced in India in 2010 in the form of human leukocyte antigen antibody screening, single antigen bead (SAB) assay and lysate-based crossmatch (LumXM) to identify low titer antibodies, which are deleterious to allograft. Instead of SAB, LumXM has been popularly used in India to identify DSAs and also called DSA crossmatch, which is not recommended or validated in International literature for denying or accepting to transplant a patient due to its fallacies. We are reporting three cases which showcase the flawed nature of this test and the implications of this test on day to day practice in 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. [ABSTRACT FROM AUTHOR]

Recently, the randomized phase‐II Triton study demonstrated that mesenchymal stromal cell (MSC) therapy facilitated early tacrolimus withdrawal in living donor kidney transplant recipients. The current sub‐study analyzed formation of de novo donor‐specific HLA antibodies (dnDSA) in the context of the degree of HLA eplet mismatches. At the time of protocol biopsy at 6 months, 7/29 patients (24%) in the MSC group and 1/27 patient (3.7%) in the control group had developed dnDSA. In the MSC group, all dnDSA were anti‐HLA‐DQ; two patients had anti‐DQ alone and five patients combined with anti‐class I, HLA‐DR or ‐DP. Despite excess dnDSA formation in the MSC‐arm of the study, the evolution of eGFR (CKD‐EPI) and proteinuria were comparable 2 years posttransplant. All dnDSA were complement‐binding and three patients had antibody‐mediated rejection in the protocol biopsy, but overall rejection episodes were not increased. Everolimus had to be discontinued in nine patients because of toxicity, and tacrolimus was reintroduced in six patients because of dnDSA formation. The HLA‐DQ eplet mismatch load independently associated with dnDSA (adjusted hazard ratio = 1.07 per eplet mismatch, p = 0.008). A threshold of ≥11 HLA‐DQ eplet mismatches predicted subsequent dnDSA in all 11 patients in the MSC group, but specificity was low (44%). Further research is warranted to explore HLA molecular mismatch load as a biomarker to guide personalized maintenance immunosuppression in kidney transplantation. [ABSTRACT FROM AUTHOR]

Torque teno virus (TTV) was recently identified as a potential biomarker for the degree of immunosuppression, and potentially as a predictor of rejection and infection in solid organ transplant patients. We evaluated TTV viral load in kidney transplant (KT) patients during the first year post-transplant to examine overall kinetics and their relationships with deleterious events, including episodes of infection and the formation of de novo donor-specific antibodies (DSAs). In a single-center, prospective observational cohort study, 81 KT patients were monitored at baseline, week 1, and month 1, 3, 6, 9 and 12, post-KT, and whenever required by clinical events. Kidney function, plasma TTV load, immunoglobulins and lymphocyte subpopulations were assessed at each time point. Twenty-six patients (32.1%) presented a total of 38 infection episodes post-KT. Induction immunosuppression with thymoglobulin, compared to basiliximab, was not associated with more infections (p = 0.8093). Patients with infectious events had lower T-cells (p = 0.0500), CD8+ T-cells (p = 0.0313) and B-cells (p = 0.0009) 1 month post-KT, compared to infection-free patients. Patients with infection also showed higher increases in TTV viral loads between week 1- month 1, post-KT, with TTV viral load variations >2.65 log10 cp/mL predicting the development of infectious events during the 12-month study period (p < 0.0001; sensitivity 99.73%; specificity 83.67%). Patients who developed de novo DSAs had lower TTV DNA viral loads at month 12 after KT, compared to patients who did not develop DSA (3.7 vs. 5.3 log10 cp/mL, p = 0.0023). Briefly, evaluating early TTV viremia is a promising strategy for defining infectious risk in the 1st year post-KT. The availability of standardized commercial real-time PCR assays is crucial to further validate this as an effective tool guiding immunosuppression prescription. [ABSTRACT FROM AUTHOR]

The presence of preformed cytotoxic donor‑specific antibodies (DSAs) has been associated with inferior allograft outcomes in the immediate posttransplant period. Since the 1970s, the primary method for determining the presence of DSAs has been the complement‑dependent cytotoxicity crossmatch. Solid phase assays on the Luminex platform were introduced in India in 2010 in the form of human leukocyte antigen antibody screening, single antigen bead (SAB) assay and lysate‑based crossmatch (LumXM) to identify low titer antibodies, which are deleterious to allograft. Instead of SAB, LumXM has been popularly used in India to identify DSAs and also called DSA crossmatch, which is not recommended or validated in International literature for denying or accepting to transplant a patient due to its fallacies. We are reporting three cases which showcase the flawed nature of this test and the implications of this test on day to day practice in transplantation. [ABSTRACT FROM AUTHOR]

Background: Donor-specific antibodies (DSAs) are IgG allo-antibodies against mismatched donor HLA molecules and can cause graft failure (GF) in the setting of haploidentical hematopoietic stem cell transplantation (haplo-HSCT). Our aim was to report the experience of the Spanish Group of Hematopoietic Transplant (GETH-TC) in DSA-positive patients who had undergone haplo-HSCT. Methods: We conducted a survey of patients who underwent haplo-HSCT in GETH-TC centers between 2012 and 2021. Data were collected on the DSA assay used, monitoring strategy, complement fixation, criteria for desensitization, desensitization strategies and transplant outcomes. Results: Fifteen centers from the GETH-TC responded to the survey. During the study period, 1,454 patients underwent haplo-HSCT. Seventy of the transplants were performed in 69 DSA-positive patients, all of whom lacked a suitable alternative donor; 61 (88%) patients were female (90% with prior pregnancies). All patients received post-transplant cyclophosphamide-based graft-versushost disease prophylaxis. Regarding baseline DSA intensity, 46 (67%) patients presented mean fluorescence intensity (MFI) >5,000, including 21 (30%) with MFI >10,000 and three (4%) with MFI >20,000. Six patients did not receive desensitization treatment, four of them with MFI <5,000. Of 63 patients receiving desensitization treatment, 48 (76%) were tested after desensitization therapy, and a reduction in intensity was confirmed in 45 (71%). Three patients (5%) experienced an increase in MFI after desensitization, two of whom experienced primary GF. Cumulative incidence of neutrophil engraftment at day 28 was 74% in a median of 18 days (IQR, 15-20); six patients died before engraftment due to toxicity or infection and eight patients had primary GF despite desensitization in seven of them. After a median follow-up of 30 months, two-year overall and event-free survival were 46.5% and 39%, respectively. The two-year cumulative incidence of relapse was 16% and nonrelapse mortality (NRM) was 43%. Infection was the most frequent cause of NRM, followed by endothelial toxicity. Multivariate analysis identified baseline MFI >20,000 as an independent risk factor for survival and an increase in titers after infusion as an independent risk factor for GF. Conclusions: Haplo-HSCT is feasible in DSA-positive patients, with high rates of engraftment after desensitization guided by DSA intensity. Baseline MFI >20,000 and increased intensity after infusion are risk factors for survival and GF. [ABSTRACT FROM AUTHOR]

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.

Anti-human leukocyte antigen (HLA) donor-specific antibodies (DSAs) are associated with antibody-mediated rejection and chronic allograft nephropathy in kidney transplantation. The interpretation of immunological assays for DSAs can be challenging due to discordant results. In this report, we present two cases of kidney transplantation involving patients with anti-HLA-C DSAs. We discuss the interpretation of their immunological tests, including complement-dependent cytotoxicity (CDC) crossmatches, flow cytometry crossmatches, and donor-specific antigen using single-antigen bead (SAB) assays, which influenced therapeutic decisions. In the first case, the patient exhibited isolated B-cell-positive crossmatch and autoantibodies, prompting the consideration of polyclonal autoantibodies in the context of underlying hepatitis C infection. The SAB assay detected only one DSA against HLA-C 03:03:01 (mean fluorescence intensity - 27,127). After careful evaluation and confirmation of negative CDC crossmatch, transplantation proceeded, and the patient demonstrated good graft function. In the second case, the patient showed a positive T-cell crossmatch along with anti-Class I HLA DSAs against HLA C*07:01 and HLA C*07:02. Despite these findings, transplantation was performed based on the absence of complement-binding antibodies. The patient experienced good graft recovery with stable kidney function. The presence of HLA-C DSAs poses challenges in transplantation decision-making. Despite conflicting studies, the pathological nature of these antibodies has been demonstrated. Careful interpretation of immunological tests and consideration of the overall clinical context are essential in making therapeutic decisions. Further research is needed to understand the clinical significance of HLA-C DSAs and their impact on graft outcomes. [ABSTRACT FROM AUTHOR]