Kidney allograft rejection is associated with an imbalance of B cells, regulatory T cells and differentiated CD28-CD8+ T cells: analysis of a cohort of 1095 graft biopsies

IntroductionThe human immune system contains cells with either effector/memory or regulatory functions. Besides the well-established CD4+CD25hiCD127lo regulatory T cells (Tregs), we and others have shown that B cells can also have regulatory functions since their frequency and number are increased in kidney graft tolerance and B cell depletion as induction therapy may lead to acute rejection. On the other hand, we have shown that CD28-CD8+ T cells represent a subpopulation with potent effector/memory functions. In the current study, we tested the hypothesis that kidney allograft rejection may be linked to an imbalance of effector/memory and regulatory immune cells.MethodsBased on a large cohort of more than 1000 kidney graft biopsies with concomitant peripheral blood lymphocyte phenotyping, we investigated the association between kidney graft rejection and the percentage and absolute number of circulating B cells, Tregs, as well as the ratio of B cells to CD28-CD8+ T cells and the ratio of CD28-CD8+ T cells to Tregs. Kidney graft biopsies were interpreted according to the Banff classification and divided into 5 biopsies groups: 1) normal/subnormal, 2) interstitial fibrosis and tubular atrophy grade 2/3 (IFTA), 3) antibody-mediated rejection (ABMR), 4) T cell mediated-rejection (TCMR), and 5) borderline rejection. We compared group 1 with the other groups as well as with a combined group 3, 4, and 5 (rejection of all types) using multivariable linear mixed models.Results and discussionWe found that compared to normal/subnormal biopsies, rejection of all types was marginally associated with a decrease in the percentage of circulating B cells (p=0.06) and significantly associated with an increase in the ratio of CD28-CD8+ T cells to Tregs (p=0.01). Moreover, ABMR, TCMR (p=0.007), and rejection of all types (p=0.0003) were significantly associated with a decrease in the ratio of B cells to CD28-CD8+ T cells compared to normal/subnormal biopsies. Taken together, our results show that kidney allograft rejection is associated with an imbalance between immune cells with effector/memory functions and those with regulatory properties

Les cellules humaines recombinantes exprimant les alloantigènes plaquettaires (nouveaux outils pour le diagnostic des thrombopénies foetales ou néonatales alloimmunes)

CHATENAY M.-PARIS 11-BU Pharma. (920192101) / SudocSudocFranceF

HLA‐EPI : A new EPIsode in exploring donor/recipient epitopic compatibilities

International audienceThe HLA system plays a pivotal role both in transplantation and immunology. While classical HLA genotypes matching is made at the allelic level, recent progresses were developed to explore antibody–antigen recognition by studying epitopes. Donor to recipient matching at the epitopic level is becoming a trending topic in the transplantation research field because anti‐HLA antibodies are epitope‐specific rather than allele‐specific. Indeed, different HLA alleles often share common epitopes. We present the HLA‐Epi tool ( hla.univ-nantes.fr ) to study an HLA genotype at the epitope level. Using the international HLA epitope registry ( Epregistry.com.br ) as a reference, we developed HLA‐Epi to easily determine epitopic and allelic compatibility levels between several HLA genotypes. The epitope database covers the most common HLA alleles ( N = 2976 HLA alleles), representing more than 99% of the total observed frequency of HLA alleles. The freely accessible web tool HLA‐Epi calculates an epitopic mismatch load between different sets of potential recipient‐donor pairs at different resolution levels. We have characterized the epitopic mismatches distribution in a cohort of more than 10,000 kidney transplanted pairs from European ancestry, which showed low number of epitopic mismatches: 56.9 incompatibilities on average. HLA‐Epi allows the exploration of epitope pairing matching to better understand epitopes contribution to immune responses regulation, particularly during transplantation. This free and ready‐to‐use bioinformatics tool not only addresses limitations of other related tools, but also offers a cost‐efficient and reproducible strategy to analyze HLA epitopes as an alternative to HLA allele compatibility. In the future, this could improve sensitization prevention for allograft allocation decisions and reduce the risk of alloreactivity

Case Report: Long-term observations from the tacrolimus weaning randomized clinical trial depicts the challenging aspects for determination of low-immunological risk patients

International audienceWhilst calcineurin inhibitors (CNI) are the cornerstone of immunosuppressive maintenance therapy in kidney transplantation, several studies have investigated the safety of CNI withdrawal in order to avoid their numerous side effects. In this context, we performed several years ago a clinical randomized trial evaluating CNI weaning in stable kidney transplant recipients without anti-HLA immunization. The trial was interrupted prematurely due to a high number of de novo DSA (dnDSA) and biopsy proven acute rejection (BPAR) in patients who underwent tacrolimus weaning, resulting in treatment for rejection and resumption of tacrolimus. We report here the long-term outcomes of patients included in this clinical trial. Ten years after randomization, all patients are alive with a functional allograft. They all receive tacrolimus therapy except one with recurrent cutaneous neoplasia issues. Long-term eGFR was comparable between patients of the two randomized groups (46.4 ml/min vs 42.8 ml/min). All dnDSA that occurred during the study period became non-detectable and all rejections episodes were reversed. The retrospective assessment of HLA DQ single molecule epitope mismatching determined that a majority of patients who developed dnDSA after tacrolimus withdrawal would have been considered at high immunological risk. Minimization of immunosuppression remains a challenging objective, mainly because of the issues to properly select very low immunological risk patients. Valuable improvements have been made the last decade regarding evaluation of the allograft rejection notably through the determination of numerous at-risk biomarkers. However, even if the impact of such tools still need to be clarify in clinical routine, they may permit an improvement in patients’ selection for immunosuppression minimization without increasing the risk of allograft rejection

Ex vivo evolution of human antibodies by CRISPR-X: from a naive B cell repertoire to affinity matured antibodies

International audienceMethodology articl

Antibody-mediated allograft rejection is associated with an increase in peripheral differentiated CD28-CD8+ T cells – Analyses of a cohort of 1032 kidney transplant recipients

International audienceBackground: CD28-CD8+ T cells represent a differentiated CD8+ T cell subset that is found to be increased in various conditions associated with chronic antigenic stimulation such as aging, chronic viral infections, autoimmune diseases, cancers, and allotransplantation.Methods: Using multivariate models, we analyzed a large cohort of 1032 kidney transplant patients in whom 1495 kidney graft biopsies were performed concomitant with a peripheral blood leukocyte phenotyping by flow cytometry. We investigated the association between the level of CD28-CD8+ T cells in the blood and the diagnosis of graft rejection according to the recent Banff classification of renal allograft pathology.Findings: We found that antibody-mediated rejection (ABMR) was associated with a significant increase in the percentage as well as the absolute number of CD28-CD8+ T cells in the peripheral blood of kidney transplant patients at the time of biopsy. The confounder-adjusted mean difference of log percentage and log absolute value between the ABMR group and the normal/subnormal histology group were 0.29 (p=0.0004) and 0.38 (p=0.0004), respectively. Moreover, we showed that CD28-CD8+ T cells from the patients diagnosed with ABMR responded more rigorously to TCR and FcγRIIIA (CD16) engagement compared to their CD28+ counterparts as evidenced by an increase in the expression of IFNγ, TNFα, and CD107a.Interpretation: Collectively, our data suggest that differentiated CD28-CD8+ T cells, with increased frequency, number, and function, may participate in the pathobiology of ABMR. Further studies are warranted to clarify the immunological role of this T cell subset in kidney graft rejection.Funding: Agence nationale de la recherche (France)

CXCR5+PD1+ICOS+ circulating T follicular helpers are associated with de novo donor-specific antibodies after renal transplantation

International audienc

EARLY EXPANSION OF TEMRA CD8 WITH INNATE-LIKE FUNCTION IDENTIFIES KIDNEY TRANSPLANT RECIPIENTS AT HIGH-RISK OF GRAFT FAILURE

Lola Jacquemont and Gaëlle Tilly are co-authorsInternational audienceAs CD8 TEMRA cells are associated with higher risk of long-term graft dysfunction, in this study, we evaluate if the monitoring of CD8-related biomarkers could improve the prognostic capacities of a clinical-based scoring system (Kidney Transplant Failure Score; KTFS). We also characterize the functionality of TEMRA and especially their reactivity upon donor-specific stimulation. 286 kidney-transplant recipients prospectively enrolled were followed for more than 8-years. 51 return in dialysis. We demonstrate that the frequency of early memory CD8 cells (EM) and TEMRA measured at 1-year post-transplantation is correlated with the risk to return in dialysis during time. For patients at high-risk of long-term graft dysfunction (according to KTFS), the use of one-year TEMRA frequency allows the discrimination of patients that will lose their graft from those that will not. Donor-specific reactivities from TEMRA and EM were similar with an early expression of CD25+CD69+CD107a+ and the high secretion of pro-inflammatory and cytotoxic molecules. Importantly, we identify an innate-like signature of TEMRA, with more than 5-fold higher expression of FCGR3A (CD16) by TEMRA as compared to NAIVE and EM. Cross-linking of CD16 triggers the secretion of TNFa and IFNg by TEMRA and their cytotoxic function and was further enhanced by the provision of IL-15. Finally, we demonstrate TEMRA and not EM display in vitro Antibody Dependent Cell Cytotoxicity conferring to TEMRA features of both adaptive and innate-like immunity and showing that anti-HLA antibodies, a major risk factor for long-term allograft outcome, could activate TEMRA in a TCR-independent manner leading to the inflammatory response

EARLY EXPANSION OF TEMRA CD8 WITH INNATE-LIKE FUNCTION IDENTIFIES KIDNEY TRANSPLANT RECIPIENTS AT HIGH-RISK OF GRAFT FAILURE

Lola Jacquemont and Gaëlle Tilly are co-authorsInternational audienceAs CD8 TEMRA cells are associated with higher risk of long-term graft dysfunction, in this study, we evaluate if the monitoring of CD8-related biomarkers could improve the prognostic capacities of a clinical-based scoring system (Kidney Transplant Failure Score; KTFS). We also characterize the functionality of TEMRA and especially their reactivity upon donor-specific stimulation. 286 kidney-transplant recipients prospectively enrolled were followed for more than 8-years. 51 return in dialysis. We demonstrate that the frequency of early memory CD8 cells (EM) and TEMRA measured at 1-year post-transplantation is correlated with the risk to return in dialysis during time. For patients at high-risk of long-term graft dysfunction (according to KTFS), the use of one-year TEMRA frequency allows the discrimination of patients that will lose their graft from those that will not. Donor-specific reactivities from TEMRA and EM were similar with an early expression of CD25+CD69+CD107a+ and the high secretion of pro-inflammatory and cytotoxic molecules. Importantly, we identify an innate-like signature of TEMRA, with more than 5-fold higher expression of FCGR3A (CD16) by TEMRA as compared to NAIVE and EM. Cross-linking of CD16 triggers the secretion of TNFa and IFNg by TEMRA and their cytotoxic function and was further enhanced by the provision of IL-15. Finally, we demonstrate TEMRA and not EM display in vitro Antibody Dependent Cell Cytotoxicity conferring to TEMRA features of both adaptive and innate-like immunity and showing that anti-HLA antibodies, a major risk factor for long-term allograft outcome, could activate TEMRA in a TCR-independent manner leading to the inflammatory response

Terminally Differentiated Effector Memory CD8+ T Cells Identify Kidney Transplant Recipients at High Risk of Graft Failure

International audienceSignificance Statement Identifying biomarkers for predicting kidney transplant failure requires better understanding of the immune response to chronic allogeneic stimulation. The authors demonstrated that 1 year after kidney transplantation, the composition of CD8 + memory T cell subsets in blood—specifically the ratio of terminally differentiated effector memory (TEMRA) and effector memory CD8 + T cells—is associated with risk for subsequent graft failure and adds predictive value to a previously reported eight-variable clinical risk score. They also found that TEMRA CD8 + T cells display a novel T cell receptor–independent mechanism of activation that is mediated through CD16 engagement and results in inflammation and antibody-dependent cellular cytotoxicity. These findings suggest a pivotal role for TEMRA CD8 + T cells in chronic humoral and cellular rejection leading to kidney transplant failure. Future clinical benefits may include the use of CD8 + memory T cell monitoring to improve risk prediction for graft failure and development of therapeutic strategies targeting TEMRA CD8 + T cells. Background Identifying biomarkers to predict kidney transplant failure and to define new therapeutic targets requires more comprehensive understanding of the immune response to chronic allogeneic stimulation. Methods We investigated the frequency and function of CD8 + T cell subsets—including effector memory (EM) and terminally differentiated EM (TEMRA) CD8 + T cells—in blood samples from 284 kidney transplant recipients recruited 1 year post-transplant and followed for a median of 8.3 years. We also analyzed CD8 + T cell reactivity to donor-specific PBMCs in 24 patients who had received living-donor kidney transplants. Results Increased frequency of circulating TEMRA CD8 + T cells at 1 year post-transplant associated with increased risk of graft failure during follow-up. This association remained after adjustment for a previously reported composite of eight clinical variables, the Kidney Transplant Failure Score. In contrast, increased frequency of EM CD8 + T cells associated with reduced risk of graft failure. A distinct TEMRA CD8 + T cell subpopulation was identified that was characterized by expression of Fc γ RIIIA (CD16) and by high levels of proinflammatory cytokine secretion and cytotoxic activity. Although donor-specific stimulation induced a similar rapid, early response in EM and TEMRA CD8 + T cells, CD16 engagement resulted in selective activation of TEMRA CD8 + T cells, which mediated antibody-dependent cytotoxicity. Conclusions At 1 year post-transplant, the composition of memory CD8 + T cell subsets in blood improved prediction of 8-year kidney transplant failure compared with a clinical-variables score alone. A subpopulation of TEMRA CD8 + T cells displays a novel dual mechanism of activation mediated by engagement of the T-cell receptor or of CD16. These findings suggest that TEMRA CD8 + T cells play a pivotal role in humoral and cellular rejection and reveal the potential value of memory CD8 + T cell monitoring for predicting risk of kidney transplant failure