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The morphologic finding of transplant glomerulitis (g) forms important evidence of microvascular injury. Besides antibody-mediated rejection (ABMR), this morphological feature is also seen in acute cellular rejection (ACR) and vasculitis but not included in the grading criteria for cellular rejection. A systematic review was thus conducted to summarize the current evidence and shed light on the quantum of impetus to be given to this finding when encountered during evaluation of renal biopsies. Out of a total of 13 studies selected, 06 studies supported the histologic finding of glomerulitis in ACR and non-DSA ABMR morphologies with variable incidence ranging from 15 to 21%. Seven studies supported glomerulitis as an independent prognostic marker for graft outcome at 1 year post transplant with or without DSA with highest HR reported of 4.52 and lowest being 01. Reviewing the present literature revealed interesting insights into occurrence, nature, molecular expression, role in glomerular injury and long-term outcomes with glomerulitis. It is recommended to approach the treatment of such lesions with heightened caution, as there appear to be elevated rates of graft failure, delayed graft function and Transplant glomerulopathy. [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.

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.

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]

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]

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]

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]

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.

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. Blood for testing was collected to tubes without anticoagulant, centrifugated at 1500 rpm per 10 minutes [5] and processed immediately (for biochemical parameters measurement) or stored at –70 °C (for antibody detection). xMAP-Luminex next generation flow cytometry technology and LABScreen Single antigen beads reagent (Onelambda, USA) were used for antiHLA determination. Analysis of results with further calculation of PRA percentage for antibodies to Class I & II separately was performed on HLAFusion 4.6 software. Briefly: patient’s serum was centrifugated at 10 000 rcf during 10 min, treated with 100 mM EDTA (Invitrogene, USA) and incubated with LABScreen beads, covered with HLA Class I &II antigens. Positive reaction was detected with second anti-human phycoerythrin (PE)-labelled IgG. The presence of antibodies to specific HLA antigen was determined by the numerical value of the mean fluorescence intensity (MFI). Serum was considered positive when PRA value was higher than 0% (PRA > 0%) and the mean MFI was higher than 600 (MFI ≥ 600). 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 and Discussion. The group of examined participants consisted patients diagnosed with different liver diseases (hepatic cirrhosis and biliary atresia). Patients therapy consisted of plasmapheresis (removal of blood plasma components, in particular anti-HLA antibodies), immunosuppressive drug “Tacrolimus” (decreases T-lymphocytes production), “Solu-Medrol” pulse therapy (synthetic glucocorticoid anti-inflammatory drug). It should be noted, that multiple transfusions before transplantation were associated with an increase in DSA and PRA levels, which increases the probability of the formation of DSA in the recipient and subsequent rejection of the transplanted organ (Figure, A). The use of the above drugs in various combinations depending on the patient’s medical history led to changes in levels of antibodies to HLA antigens and blood biochemical parameters. Before graft rejection we observed high values of PRA, DSA and increased level of key biochemical parameters in bloodstream, which indicated start of liver disfunction development. It should be noted, that levels of PRA and DSA grew earlier than ALT and AST activity (Figure, В) and total bilirubin concentration (Figure, С). We can speculate, that PRA increase as well as de novo generated DSA can be the reason of graft rejection, which was confirmed by the changes of key biochemical markers of liver functioning (Figure 1, B, C). We observed directly proportional dependence between biochemical blood parameters and PRA and DSA. They have the same trend of growth and decline depending on the effectiveness of the therapy. After immunosuppression therapy, DSA were not detected, blood biochemical parameters returned to normal reference values (total bilirubin = 15 μmol/L; AST = 40 IU/L; ALT = 45 IU/L), however, general anti-HLA antibodies level was still present therefore antibody monitoring should be continued to prevent the possibility of graft rejection and to adjust immunosuppression protocols. 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. [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]

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 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]

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]

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]

Pretransplant immunological assessment of a transplant donor has evolved significantly over the last few decades with the advent of testing platforms with enhanced sensitivity and varying formats. The single antigen bead assay (SAB) assay, a virtual crossmatch (vXM) is used extensively and considered the gold standard for defining donorspecific antibodies (DSA) in many parts of the World. A country like India, is however challenged by the lack of adequate representation of locally frequent HLA alleles and hence in our institution, we continue to perform a physical crossmatch (pXM) on the Complement Dependent Cytotoxicity and flow cytometry platforms alongside the SAB. We report here a case report where the discrepancy between platforms of testing have raised certain pertinent questions in our interpretation of the vXM. [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.

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.

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]

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]

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]

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 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.

Resumen: Introducción: No existe consenso sobre el tratamiento más adecuado para el rechazo humoral crónico activo (RHCa). Estudios recientes sugieren que el tratamiento con tocilizumab (TCZ) puede estabilizar la función del injerto, disminuir la intensidad de los anticuerpos anti-HLA donante-específicos (ADEs) y reducir la inflamación de la microcirculación. Pacientes y métodos: Estudio observacional con pacientes trasplantados renales diagnosticados de RHCa (n = 5) que no habían presentado respuesta al tratamiento tradicional basado en la combinación de recambios plasmáticos, inmunoglobulinas y rituximab. A los pacientes se les indicó tratamiento con TCZ como uso compasivo en seis dosis mensuales (8 mg/kg/mes). Durante el seguimiento se monitorizó la función renal, proteinuria y la intensidad de los ADEs. Resultados: Cinco pacientes, de edad media 60 ± 13 años, tres de género masculino y dos retrasplantes (cPRA medio 55%) con ADEs preformados. El tratamiento con TCZ se inició a los 47 ± 52 días de la biopsia. En dos casos se suspendió el tratamiento tras la primera dosis, por bicitopenia severa con viremia por citomegalovirus y por fracaso del injerto, respectivamente. En los tres pacientes que completaron el tratamiento no se observó estabilidad de la función renal (creatinina sérica [Cr-s] de 1,73 ± 0,70 a 2,04 ± 0,52 mg/dL, filtrado glomerular estimado [FGRe] de 46 ± 15 a 36 ± 16 mL/min), presentaron aumento de la proteinuria (3,2 ± 4,0 a 6,9 ± 11,0 g/g) y la intensidad de los ADEs se mantuvo estable. No se observaron cambios en el grado de inflamación de la microcirculación (glomerulitis y capilaritis peritubular [g+cpt] 4,2 ± 0,8 vs. 4,3 ± 1,0), ni en el grado de glomerulopatía del trasplante (glomerulopatía crónica [cg] 1,2 ± 0,4 vs. 1,8 ± 1,0). Conclusiones: La terapia con TCZ no parece ser eficaz en modificar la historia natural del rechazo humoral crónico activo, no mejora el grado de la inflamación de la microcirculación ni reduce la intensidad de ADEs. Abstract: Introduction: There is no consensus on the most appropriate treatment for chronic active antibody-mediated rejection (cAMR). Recent studies suggest that treatment with tocilizumab (TCZ) may stabilize graft function, decrease the intensity of donor-specific HLA antibodies (DSAs) and reduce inflammation of microcirculation. Patients and methods: Observational study with renal allograft recipients diagnosed with cAMR (n = 5) who had not submitted a response to traditional treatment based on the combination of plasma replacements, immunoglobulins, and rituximab. Patients were told to be treated with TCZ as compassionate use in six doses per month (8 mg/kg/month). Renal function, proteinuria, and the intensity of DSAs were monitored during follow-up. Results: Five patients, average age 60 ± 13 years, three male and two retrasplants (cPRA average 55%) with preformed DSAs. Treatment with TCZ was initiated within 47 ± 52 days of biopsy. In two cases treatment was discontinued after the first dose, by severe bicitopenia with cytomegalovirus viremia and by graft failure, respectively. In the three patients who completed treatment, no stability of renal function (serum creatinine from 1.73 ± 0.70 to 2.04 ± 0.52 mg/dL, e-FGR 4 6 ± 15 to 36 ± 16 mL/min), showed increased proteinuria (3.2 ± 4.0 to 6.9 ± 11.0 g/g) and the intensity of DSAs maintain stable. No changes were observed in the degree of inflammation of microcirculation (g + pt 4.2 ± 0.8 vs. 4.3 ± 1.0) or in the degree of transplant glomerulopathy (cg 1.2 ± 0.4 vs. 1.8 ± 1.0). Conclusions: TCZ therapy does not appear to be effective in modifying the natural history of chronic active antibody-mediated rejection, does not improve the degree of inflammation of microcirculation and does not reduces the intensity of DSAs.

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

Aims The epidemiology of sudden cardiac death (SCD) after heart transplantation (HTx) remains imprecisely described. We aimed to assess the incidence and determinants of SCD in a large cohort of HTx recipients, compared with the general population. Methods and results Consecutive HTx recipients (n = 1246, 2 centres) transplanted between 2004 and 2016 were included. We prospectively assessed clinical, biological, pathologic, and functional parameters. SCD was centrally adjudicated. We compared the SCD incidence beyond the first year post-transplant in this cohort with that observed in the general population of the same geographic area (registry carried out by the same group of investigators; n = 19 706 SCD). We performed a competing risk multivariate Cox model to identify variables associated with SCD. The annual incidence of SCD was 12.5 per 1,000 person-years [95% confidence interval (CI), 9.7–15.9] in the HTx recipients cohort compared with 0.54 per 1,000 person-years (95% CI, 0.53–0.55) in the general population (P < 0.001). The risk of SCD was markedly elevated among the youngest HTx recipients with standardized mortality ratios for SCD up to 837 for recipients ≤30 years. Beyond the first year, SCD was the leading cause of death. Five variables were independently associated with SCD: older donor age (P = 0.003), younger recipient age (P = 0.001) and ethnicity (P = 0.034), pre-existing donor-specific antibodies (P = 0.009), and last left ventricular ejection fraction (P = 0.048). Conclusion HTx recipients, particularly the youngest, were at very high risk of SCD compared with the general population. The consideration of specific risk factors may help identify high-risk subgroups. [ABSTRACT FROM AUTHOR]

Background: The main objective of this study was to determine the results of the cell-based assay (CDC-XM and FC-XM), and correlate with the results of solid phase assay (L-SAB). Methods. In this retrospective study, 350 prospective renal transplant recipients were tested for the presence of HLA antibodies by CDC-XM, FC-XM and L-SAB screening with their corresponding donor. Results: T-cell-FC-XM showed a sensitivity of 71.43% and a specificity of 91.50% for detecting class I L-SAB (+), while B-cell-FCXM showed a sensitivity of 94.94% and a specificity of 61.99% for detecting class II L-SAB (t). On the other hand, T-CDC-XM showed a sensitivity of 32.14% and a specificity of 98.64% for detecting class I L-SAB (-4-), while B-CDC-XM showed a sensitivity of 44.30% and a specificity of 94.83% for detecting class H L-SAB (-). In this study, the results indicated that DSA class I MFI value of 2845 and above significantly (p 50.001) correlated with T-cell-FC-XM positivity, while MFI value of 4585 and above (p 50.001) showed strong predictive accuracy of a positive T-cell-CDC-XM. However, DSA class II MFI cut-off of 1988 and above significantly (p 50.001) correlated with B-cell-FC-XM positivity, while MFI value of 5986 and above (p %0.001) showed strong predictive accuracy of a positive B-cell-CDC-XM. Conclusions: Our study showed that CDC-XM has poor sensitivity, while FC-XM has poor specificity to detect DSA. L-SAB has good correlation with T-cell-FC-XM (p < 0.0001) but not with B-cell-FC-XM (P = 0.31). DSA strength >2845 and > 1988 significantly correlated with T-cell-FC-XM positivity and B-cell-FC-XM positivity, respectively. While, a MFI value of >4585 and > 5986 significantly correlated with T-tell-CDC-XM posilivity and Bcell- CDC-XM positivity, respectively. These MFI cut-off values could serve as a surrogate marker for CDC-XMl and FC-XM tests and may help in resolving the limitations of cell-based techniques. Iii conclusion, we found that LSAB is more sensitive and specific than CDC-XM and FC-XM and therefore may be used as a test of choice. [ABSTRACT FROM AUTHOR]

BackgroundDonor-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.MethodsWe 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.ResultsFifteen 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-versus-host 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 20,000 as an independent risk factor for survival and an increase in titers after infusion as an independent risk factor for GF.ConclusionsHaplo-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.

Background Despite substantial improvements in short-term kidney allograft survival, median long-term survival remains at a standstill. It is unclear whether and to what extent a transplant centre's post-transplant care influences long-term outcomes. Methods We retrospectively analysed 501 single kidney transplant recipients (KTRs) who underwent transplantation between 2009 and 2018 and did not develop rejection or de novo donor-specific antibodies (dnDSA) within the first post-transplant year. After that, KTRs were either followed exclusively every 3 months by the transplant centre (n  = 197) or every 3 months by local nephrologists (n  = 304) with only yearly follow-up by the transplant centre. We analysed kidney allograft outcomes regarding estimated glomerular filtration rate (eGFR) decline, proteinuria, development of dnDSA and rejection. Results No differences between the two groups were observed in the baseline characteristics and the characteristics at the end of the first post-transplant year (P  > .05). KTRs followed by local nephrologists were comparable to KTRs followed by the transplant centre concerning patient survival (P  = .541), kidney allograft survival (P  = .385), eGFR decline (P  = .488), progression of proteinuria (P  > .05), the development of dnDSA (P  = .335) and T-cell-mediated rejection (P  = .480). KTRs followed by the transplant centre were more likely to undergo indication biopsies in case of allograft dysfunction and dnDSA (P  < .001). Antibody-mediated rejection was diagnosed earlier and more frequently (P  = .059), recurrent glomerulonephritis was diagnosed earlier and more frequently (P  = .026) and immunosuppression was modified earlier and more frequently in response to histological findings (P  = .038). Conclusions Our findings suggest that close collaboration between local nephrologists and the transplant centre ensures good allograft outcomes independent of the caregiver. Greater biopsy activity in the transplant centre allows for earlier diagnosis of allograft dysfunction as the basis for novel treatment options. [ABSTRACT FROM AUTHOR]

Background: The impact of donor-specific antibodies (DSA) in (highly-) immunized living donor kidney transplant recipients is reported differentially in various patient cohorts. Methods: We have performed a retrospective analysis of all consecutive HLAincompatible living donor kidney transplant recipients in our center between 2010-2019. Recipients who underwent plasmafiltration for a positive CDCcrossmatch were excluded. For each DSA+ recipient (DSA+), one immunized recipient without DSA (pPRA+) and two non-immunized recipients (pPRA-) were included. Patient and graft survival were analyzed and a subgroup analysis of DSA+ recipients was performed. Results: For 63 DSA+ recipients, 63 PRA+ and 126 PRA- recipients were included. 26 (41%) had class I, 24 (38%) class II and 13 (21%) combined HLA class I and II DSA. Death-censored graft survival was inferior in DSA+ recipients compared to pPRA+ (HR 2.38 [95% CI 1.00-5.70]) as well as to pPRA- (HR 3.91 [1.86-8.22]). In multivariate analysis, DSA remained of negative influence on death-censored graft survival. Flowcytometric crossmatch, MFI value, HLA class and origin of DSA were not of significant impact. Conclusion: In our cohort of (highly-) immunized recipients, pretransplant DSA led to inferior death-censored graft survival. There were no "safe" DSA characteristics since only DSA per se impacted death-censored graft survival. [ABSTRACT FROM AUTHOR]

Background Patients awaiting solid organ transplantation may develop anti-HLA antibodies after sensitization events such as transfusions, pregnancies, or previous transplantations. However, the effects of a particular sensitization event on HLA alloimmunization have not been well studied in parallel using cell-based assays and solid-phase assays. In this study, we evaluated and compare how different sensitization events affect the HLA antibody screening (HLA-Ab) and donor specific antibody (DSA) status in solid renal organ transplantation patients. Methods HLA antibody (HLA-Ab) screening tests like complement-dependent cytotoxicity crossmatch (CDC-XM), flow cytometry crossmatch (FC-XM) and Luminex panel-reactive antibody (L-PRA) were performed in all 1066 patients (635 males and 431 females). If any of these tests turned out to be positive, a Luminex single antigen bead (L-SAB) assay was performed for DSA identification. Test positive rates and antibody strengths were analyzed according to the different sensitization events and gender. Results In this study, HLA-Ab screening tests positive rates (L-PRA, FC-XM and CDC-XM) were significantly higher in patients with previous transplantation (73.91%, 100% and 56.52% p < 0.001), previous pregnancy (57.46%, 70.14% and 18.85% p < 0.001) or blood transfusion (27.33%, 35.55% and 7.33% p < 0.001) compared with patients without a sensitizing event (6.17%, 13.58% and 1.09). In this study, re-transplantation group showed significantly stronger antibody strength (DSA) than non sensitized group (class I and II MFI 11418.04, 17,837.78 vs class I and II MFI 2659, 3329; P < 0.001) and those with single sensitization events of transfusion (class I and II MFI 11418.04, 17,837.78 vs class I and II MFI 5790.26, 6004.16; P < 0.001) or pregnancy (class I & II MFI 11418, 17,837 vs class I and II MFI 8631.71, 7253.29; P < 0.001). Conclusions Pregnancy and blood transfused had high allo-immunization rate for class I HLA antigens. While re-transplantation patients had high allo-immunization rate for both the HLA classes (HLA- class I and HLA- class II). Re-transplantation group showed significantly stronger antibody strength, followed by pregnancy and then transfusion. [ABSTRACT FROM AUTHOR]