Littérature scientifique sur le sujet « Allo-reactivity »

Abstract Reactivations of cytomegalovirus (CMV), Epstein Bar virus (EBV) and adenovirus (AdV) are frequently seen in immune compromised patients after allogeneic stem cell transplantation (alloSCT), and are associated with high morbidity and mortality. T cell immunity is essential for anti-viral protection, but a fully competent T cell repertoire generally does not develop until 3-6 months after transplantation. Especially patients transplanted with a virus non- experienced donor are at risk of developing severe complications. Adoptive transfer of partially HLA-matched virus specific T cells from healthy third party donors is a potential strategy to temporarily provide anti-viral immunity to these patients. However, these partially HLA-matched T cells harbor a risk of mediating allo-HLA cross-reactivity. Here, we investigated whether virus specificity and HLA restriction of the virus specific T cells influence the risk of allo-HLA cross-reactivity, and thus the development of GVHD. To determine the occurrence and diversity of allo-HLA cross-reactivity, virus specific CD8 T cells from homozygous HLA-A*01:01/B*08:01 and HLA-A*02:01/B*07:02 donors were isolated by cell sorting using tetramers for various peptides from CMV, EBV and AdV. Allo-HLA cross-reactivity was tested using an allogeneic EBV-LCL panel covering 116 different HLA molecules and confirmed using K562 cells retrovirally transduced with single HLA alleles of interest. A significant proportion of the virus specific T cell populations (n=174; 20 specificities) isolated from 27 healthy donors exerted allo-HLA cross-reactivity, as measured by recognition of 1 or more HLA mismatched EBV-LCLs from the panel. Similar frequencies were found for the various viral specificities showing 30% of the CMV, 46% of the EBV and 36% of the AdV-specific T cell populations to be allo-HLA cross-reactive. However, for some specificities (e.g. HLA-A*0201-restricted EBV-LMP2-FLY) allo-HLA cross-reactivity was infrequent (n=1/11), whereas for other specificities (e.g. HLA-B*08:01-restricted EBV-BZLF1-RAK) the majority of the T cell populations (n=9/13) was allo-HLA reactive. Surprisingly, a much larger fraction of HLA-B*08:01 restricted virus specific T cell populations showed allo-HLA cross-reactivity (72%, 36 out of 50 T cell lines), compared to the other HLA restricted virus specific T cell populations (29% of HLA-A*01:01, 30% of HLA-A*02:01 and 26% of HLA-B*07:02 restricted virus specific T cell lines). HLA-B*08:01 restricted virus specific T cells also exhibited the broadest allo-HLA reactivity, reacting to a median of 5 allo EBV-LCLs (range 1-17). In contrast, HLA-A*01:01, HLA-A*02:01 and HLA-B*07:02 restricted virus specific T cells reacted to a median of 1, 2 and 3 (ranges 1-7) allo EBV-LCLs, respectively. Dissection of the diversity/specificity of the allo-HLA reactivity using the panel of 40 different single HLA transduced K562 cells further illustrated the extensive allo-HLA cross-reactivity for HLA-B*08:01 restricted T cells isolated from homozygous HLA-A*01/B*08 donors compared to virus specific T cells restricted by other HLA alleles. These data show that allo-HLA cross-reactivity by virus specific T cells is highly influenced by the HLA restriction and not by the viral specificity of the T cell populations. Of the HLA-A*01, A*02, B*07 and B*08-restricted virus specific T cell populations isolated from homozygous donors, HLA-B*08:01 restricted virus specific T cells showed the highest frequency and diversity of allo-HLA cross-reactivity. Our results indicate that selection of virus specific T cells with specific HLA restrictions may decrease the risk of developing GVHD after infusion of third-party virus specific T cells to patients with uncontrolled viral reactivation after alloSCT. Disclosures No relevant conflicts of interest to declare.

Previous studies have shown that T cell clones specific for strong Mlsa,d determinants concomitantly display apparently random reactivity to allo-H-2 determinants. One explanation for this finding is that T cell recognition of Mlsa,d and allo-H-2 determinants is controlled by separate sets of receptors. If these receptors were chromosomally unlinked, karyotypically unstable T cell hybrids with dual reactivity for Mlsa,d and particular allo-H-2 determinants would be expected, occasionally, to lose reactivity for one set of determinants, but not the other. The results presented here provide direct support for this prediction.

Abstract Graft-versus-host disease and graft rejection are major complications of allogeneic HLA-mismatched stem cell transplantation or organ transplantation that are caused by alloreactive T cells. Because a range of acute viral infections have been linked to initiating these complications, we hypothesized that the cross-reactive potential of virus-specific memory T cells to allogeneic (allo) HLA molecules may be able to mediate these complications. To analyze the allo-HLA reactivity, T cells specific for Epstein-Barr virus, cytomegalovirus, varicella zoster virus, and influenza virus were tested against a panel of HLA-typed target cells, and target cells transduced with single HLA molecules. Eighty percent of T-cell lines and 45% of virus-specific T-cell clones were shown to cross-react against allo-HLA molecules. The cross-reactivity of the CD8 and CD4 T-cell clones was directed primarily against HLA class I and II, respectively. However, a restricted number of CD8 T cells exhibited cross-reactivity to HLA class II. T-cell receptor (TCR) gene transfer confirmed that allo-HLA reactivity and virus specificity were mediated via the same TCR. These results demonstrate that a substantial proportion of virus-specific T cells exert allo-HLA reactivity, which may have important clinical implications in transplantation settings as well as adoptive transfer of third-party virus-specific T cells.

Reactivations of cytomegalovirus (CMV), Epstein Barr virus (EBV) and adenovirus (AdV) occur frequently in immune compromised patients after allogeneic stem cell transplantation (alloSCT) and cause high morbidity and mortality. T-cell immunity is essential for anti-viral protection, but a fully competent T-cell repertoire generally does not develop until 3-6 months after transplantation. Especially patients transplanted with a graft from a virus non-experienced donor are at risk. Adoptive transfer of partially HLA-matched virus-specific T cells from healthy third party donors is a potential strategy to temporarily provide anti-viral immunity to these patients. However, such T cells harbor a risk of mediating off-target toxicity due to allo-HLA cross-reactivity. It is not currently known whether the degree of allo-HLA cross-reactivity is random or whether rules exist that might allow prediction of specific T-cell populations. Here, we investigated whether virus specificity, HLA type of the donor or HLA restriction of the virus-specific T cells influence the risk of allo-HLA cross-reactivity. Through cell sorting using tetramers for various peptides from CMV, EBV and AdV, 164 CD8 T-cell populations (21 specificities) were isolated from peripheral blood of 24 healthy donors, homozygous for HLA-A*01:01/B*08:01 and HLA-A*02:01/B*07:02. Allo-HLA cross-reactivity was tested using an allogeneic EBV-LCL panel covering 116 different HLA molecules and confirmed using K562 cells retrovirally transduced with single HLA alleles of interest. Forty percent of all virus-specific T-cell populations exerted allo-HLA cross-reactivity. Similar frequencies were found for the various viral specificities showing 33% of the CMV, 43% of the EBV and 38% of the AdV-specific T-cell populations to be allo-HLA cross-reactive. Surprisingly, a much larger fraction of the HLA-B*08:01-restricted virus-specific T-cell populations exhibited allo-HLA cross-reactivity (77%) than from those restricted by the other HLAs (32% of HLA-A*01:01, 38% of HLA-A*02:01 and 26% of HLA-B*07:02-restricted virus-specific T-cell populations). HLA-B*08:01-restricted virus-specific T cells also exhibited the broadest allo-HLA reactivity, reacting to a median of 5 different allogeneic EBV-LCLs (range 1-17). In contrast, HLA-A*01:01, HLA-A*02:01 and HLA-B*07:02-restricted virus-specific T cells reacted to a median of 1, 2 and 3 (range 1-7) different allogeneic EBV-LCLs, respectively. Dissection of the diversity/specificity of the allo-HLA reactivities using a panel of 40 different single HLA-A, B, or C-transduced K562 cells further illustrated recurrent recognition of a restricted group of allogeneic HLA-B molecules by HLA-B*08:01-restricted T-cell populations, mediated by single T-cell clones. Heterozygosity for recurrently recognized allo-HLA-B molecules led to a significant decrease in the broadness of allo-HLA cross-reactivity by HLA-B*08:01-restricted T-cell populations, presumably due to negative thymic selection. In contrast, heterozygosity HLA-B molecules that were not part of the restricted group of cross-recognized alleles did not significantly decrease allo-HLA cross-reactivity. These data show that allo-HLA cross-reactivity by virus-specific T cells is highly influenced by their HLA restriction and the HLA background of the donors, but not by their virus specificity. Of the HLA-A*01, A*02, B*07 and B*08-restricted virus-specific T-cell populations isolated from homozygous donors, HLA-B*08:01-restricted virus-specific T cells showed the highest frequency and diversity of allo-HLA cross-reactivity with recurrent recognition of groups of specific mismatched allogeneic HLA-B alleles. Our results indicate that selection of virus-specific T cells with specific HLA restrictions and HLA backgrounds may decrease the risk of off-target toxicity after infusion of third-party virus-specific T cells to patients with uncontrolled viral reactivation after alloSCT. Disclosures No relevant conflicts of interest to declare.

Abstract Allo-reactive natural killer (NK) cells frequently occur early after haplo-mismatch hematopoietic stem cell transplantation (HSCT) with killer cell immunoglobuline-like receptor (KIR)-ligand mismatch in graft versus host (GvH) direction. Clinical data and experiments in mice indicate a beneficial influence on relapse rates, graft acceptance and Graft-versus-Host disease (GvHD). We determined the incidence of allo-reactive donor type NK cells after HLA A-, B-, DR-, DQ-matched allogeneic HSCT on a functional level. Clinical course, chimerism (PCR), immune-reconstitution (FACS) and frequencies of functional active and allo-reactive NK cells (ELISpot) were longitudinal determined in 19 patients so far. Patients (pts) suffered for high risk AML (7 pts), CML failing cytogenetic response to imatinib (3 pts), poor risk ALL (2 pts), relapse/refractory high-grade NHL (6 pts) and Multiple Myeloma (13q-) (1 pt). All patients received myeloablative conditioning regimens and GvHD-prophylaxis with cyclosporine A or tacrolimus and short course mycophenolat mofetil without in vivo or ex vivo T cell depletion. Chimerism analyses ensured hematopoietic reconstitution from donor type in 19/19 patients. In 3/19 patients NK cell activity was absent even against HLA class I negative control target cells. Absence of functional active NK cells correlates with severe acute GvHD accompanied by high doses of glucocorticosteroid medication. In all other patients we detected at least once functional active NK cells in peripheral blood. In 4/19 cases we detected allo-reactive NK cells after HSCT at days (d) +28, +68, +128 (case 19), d +56 (case 8), d +355 (case 1) and d +379 (case 13). Two cases were transplanted in KIR-ligand mismatch in GvH direction (donors HLA-CAsn80 and -CLys80, recipients missing HLA-CLys80). Allo-reactive NK cells were absent in all patients with known complete KIR-ligand match. Flow cytometry data on reconstitution of NK cell repertoire showed individual heterogeneous results. After median observation time post HSCT of 268 d (31–902) 3 patients died due to relapse. None of the patients with NK cell allo-reactivity experienced relapse. This is the first proof of circulating functionally active, allo-reactive NK cells after HLA-A, -B, -DR and -DQ matched HSCT. We detected NK cell allo-reactivity in all donor-recipient pairs with KIR-ligand (HLA-C) mismatch in GvH direction. After haplo-mismatch HSCT and T cell depletion NK cell allo-reactivity is restricted early after transplantation (within 3 months). In contrast, we detected late onset (>1 year) of NK cell allo-reactivity after one-locus (HLA-C) mismatch HSCT without T cell depletion of the grafts.

Abstract To see k information on T cell recognition of Mlsa determinants, hybridomas were prepared from a well-characterized F23.2+ (V beta 8.2+) T cell clone specific for three different ligands, i.e., 1) Mlsa determinants, 2) fowl gamma-globulin (F gamma G) plus self-H-2 (H-2d), and 3) allo-H-2, e.g., H-2p, determinants. Fusion of the clone to the BW5147 thymoma line produced a triple-reactive T hybridoma which generated two types of spontaneous variants. One type of variant (type I) lost Mlsa reactivity but retained reactivity to both F gamma G/H-2d and allo-H-2p. These variants, which were generated at high frequency, stained strongly with a mAb, A1.57, with idiotypic specificity for the TCR molecules of the parental clone. The second type of variant (type II) reacted to Mlsa determinants but showed no reactivity to F gamma G/H-2d or to allo-H-2p. These variants failed to express the A1.57 idiotypic determinants of the parent clone, but were F23.2+ (V beta 8.2+); nonequilibrium pH gradient electrophoresis analysis suggested that these hybrids expressed a mixed TCR heterodimer composed of the parental clone beta-chain and the BW5147 alpha-chain. Three aspects of the data are very difficult to accommodate with the view that Mlsa, F gamma G, and allo-H-2 determinants are all recognized via a common TCR molecule: 1) the independent (and frequent) segregation of Mlsa reactivity from F gamma G/H-2d and allo-H-2p reactivity, 2) the retention of Mlsa reactivity by the type II variants despite loss of the parental clone alpha-chain, and 3) the loss of Mlsa reactivity by the type I variants despite high expression of the A1.57+ TcR molecules derived from the parental clone. The data support a model in which Mlsa determinants are recognized by a separate T cell structure, which we envisage as a monomorphic accessory molecule unrelated to the TCR. Since the type II hybridoma variants invariably retained quantitatively normal TcR expression, the triggering phase of anti-Mlsa responses appears to be TCR dependent. The model we favor is that anti-Mlsa/Mlsa interaction increases TCR binding with Ia epitopes to above the threshold required for cell triggering. A key feature of this model is that Mlsa and Ia determinants are recognized as separate structures rather than as a complex.

Abstract T cell-depleted allogeneic stem cell transplantation (alloSCT) is applied in patients with hematological malignancies to reduce the risk of graft versus host disease (GvHD), but the associated increased risk of infections and disease relapse makes scheduled donor-lymphocyte-infusion (DLI) necessary. Since HLA-DP is not taken into account in the matching procedure, stem cell grafts from unrelated donors are often only 10/10 matched, and mismatched for HLA-DP. Under non-inflammatory conditions, expression of HLA-DP is restricted to hematopoietic cells. Therefore, treatment with HLA-DP mismatched donor CD4 T cells can induce a specific graft versus leukemia (GvL) effect. However, in some cases, patients receiving HLA-DP mismatched CD4 T cells suffer from GvHD mediated by a profound allo-HLA-DP specific immune response. Adoptive transfer of in-vitro selected allo-HLA-DP restricted donor T cells directed against antigens specifically expressed on hematopoietic cells may be an elegant strategy to induce a specific GvL effect without coinciding GvHD. To investigate the feasibility of this approach, the allo-HLA-DP restricted T cell repertoire was dissected to unravel potential tissue specificities and to investigate the presence of hematopoiesis-specific CD4+ T cells with therapeutic value within this compartment. To induce allo-HLA-DP directed T cell responses, HLA-DP mismatched (10/10 matched) donor/patient pairs were selected. Donor PBMC were co-cultured with patient mature monocyte-derived dendritic cells (DC) for 14 days. The donor cells were first re-stimulated with autologous DC and depleted of activated auto-reactive CD137+ T cells using magnet cell separation (MACS). The negative fraction was then stimulated with the HLA-DP mismatched patient DC to induce activation of allo-reactive T cells. These allo-reactive CD137+ CD4+ T cells were clonally isolated using flowcytometric cell sorting, and expanded. Allo-HLA-DP restricted recognition of different hematopoietic and non-hematopoietic stimulator cells by the T cell clones was assessed using IFNγ and IL-4 ELISA. The T cells were tested against a large panel of hematopoietic cells (monocytes, DC, EBV-LCL and PHA blasts) of donor and patient origin, leukemic cell samples (AML) and non-hematopoietic cells (IFNγ pretreated, HLA-class-II expressing, skin-derived fibroblasts, and target-HLA-DPB1-transduced HELA, lung, kidney, and colon carcinoma cell lines). After re-stimulation with patient DC, flowcytometry showed frequencies of 0.5-10% of allo-DC activated (CD137+) CD4+ T cells. After cell sorting 1521 T cell clones from 4 different HLA-DP mismatched patient/donor pairs were tested against donor EBV-LCL, donor DC, patient EBV-LCL and patient DC as initial screening for allo-reactivity. 80% of the T cell clones showed allo-reactivity, as defined by recognition of patient, but not donor-derived EBV-LCL and/or DC. 14% of the tested clones showed no reactivity and 6% were auto-reactive. The HLA-DP restriction was analyzed of 400 selected allo-reactive T cell clones, using a panel consisting of donor, patient and 3rd party EBV-LCL or DC, 3rd party fibroblasts and target HLA-DPB1 transduced HELA cells. Of these 400 T cell clones, 65% were confirmed to be HLA-DP restricted. From these allo-HLA-DP restricted T cell clones 80% recognized both hematopoietic and non-hematopoietic cells expressing the target allo-HLA-DPB1. The other 20% of the allo-HLA-DP restricted T cell clones only produced cytokines when stimulated with hematopoietic cells (EBV-LCL and/or DC), and not when stimulated with non-hematopoietic cells (Fibroblasts, HELA, carcinoma cell lines). Moreover, 40% of these T cell clones showing hematopoiesis-restricted recognition only recognized DC, but not EBV-LCL expressing the target HLA-DPB1 allele. These clones also recognized primary AML blasts and proliferating CD34+ progenitor cells, illustrating a myeloid lineage restricted recognition pattern. These results illustrate that reactivity of allo-HLA-DP restricted T cells is not only determined by the expression of the target HLA-DPB1 allele, but is also dictated by cell lineage-specific gene expression causing differential peptide expression in HLA-DPB1. As a result, a significant portion of the allo-HLA-DP specific T cell repertoire harbors a specific GvL recognition pattern with high therapeutic value. Disclosures No relevant conflicts of interest to declare.

Abstract Abstract 647 Background: Donor lymphocyte infusions (DLI) has limited efficacy and is associated with substantial graft vs host disease (GVHD) in treating relapse after allogeneic BMT (alloBMT) in large part due to the absence of significant tumor specificity. Thus, novel strategies are required that increase the tumor specificity with reduced alloreactivity. High-dose Cy post-BMT effectively reduces GVHD through early elimination of allo-reactive T cells and enables immune reconstitution free of ongoing pharmacologic immunosuppression. Since the BM is both the site of disease in most hematologic malignancies and a reservoir of tumor specific T cells, we hypothesized that marrow infiltrating lymphocytes (MILs) collected after alloBMT in patients treated with high-dose Cy could be a source of tumor-specific T cells for adoptive immunotherapy. Methods: BM was obtained from patients 2 –12 months after HLA-matched alloBMT on the clinical trial using high-dose post-transplant Cy as a single agent GVHD prophylaxis. The MILs were activated and expanded with CD3/CD28 antibody-coated beads. Results: Allo-MILs can be reproducibly expanded (574-fold avg expansion; 14–2000) at all time points tested. The activated allo-MILs are not anergic, exhibit anti-HLA-reactivity against third party allo-antigens but do not respond to recipient allo-antigens. Tumor-specific MILs were significantly expanded as determined by reactivity to HL60/K562 myeloid cell lysates (P<0.0001; pre- vs. post-activation). In contrast, no change was observed in cultures pulsed with irrelevant antigens, thus suggesting the specificity of the response. The ability to expand allogeneic antigen-specific MILs was also confirmed with a 15.5 fold expansion of PR-1 specific (HLA) A*0201-restricted CD8+ T-cells using tetramers. Conclusions: We can augment the tumor-specificity of MILs obtained post-transplant with minimal allo-reactivity in patients treated with post-BMT high-dose Cy. This could represent a novel approach to highly tumor-specific DLI. A phase I/II trial is planned to assess the safety and feasibility of administering ex vivo expanded post-transplant, allogeneic MILs to patients with relapsed hematologic malignancies after alloHSCT. Disclosures: No relevant conflicts of interest to declare.

La transplantation rénale est le meilleur traitement de l’insuffisance rénale chronique terminale, que ce soit en termes d’espérance ou de qualité de vie. Malgré les progrès réalisés en immunologie de la transplantation et dans la gestion globale des patients transplantés, la principale étiologie de perte de greffon reste le rejet, et en particulier le rejet humoral.L’évaluation du risque de rejet humoral repose principalement sur le dosage des anticorps anti-HLA dirigés contre le greffon. Pourtant, il apparait que ces anticorps ont un faible pouvoir prédictif de l’incidence et du pronostic du rejet, ce qui pourrait être expliqué par une hétérogénéité de leurs caractéristiques intrinsèques. Ces caractéristiques dépendent des cellules responsables de leur sécrétion, plasmocytes à courte et longue durée de vie, et donc indirectement des cellules responsables du maintien du pool de ces cellules sécrétrices d’anticorps : les lymphocytes B mémoires. Il a été montré en pathologies infectieuses que ces lymphocytes B mémoires sont hétérogènes en termes de phénotype, de fonction, de degré de clonalité et de diversification de leur BCR (B-cell receptor). Néanmoins, ceci n’a pas encore été analysé en transplantation rénale. Un des objectifs de cette thèse était d’étudier le degré d’hétérogénéité des lymphocytes B mémoires HLA-spécifiques chez des patients immunisés en attente de transplantation rénale. Pour ce faire, une analyse en cellule unique de lymphocytes B mémoires HLA-spécifiques de patients présentant différents contextes et degré d’immunisation a été réalisée, dans le but d’identifier leurs caractéristiques phénotypiques et transcriptomiques et la diversification de leur répertoire BCR.La deuxième partie des travaux s’est concentrée sur les modalités diagnostiques du rejet de greffe rénale. Depuis quelques années, des outils de biologie moléculaire sont disponibles, permettant d’évaluer des centaines de transcrits exprimés dans le tissu de biopsie. Ces outils donnent la possibilité de décrire de nouvelles voies physiopathologiques, et potentiellement d’améliorer le diagnostic du rejet, en particulier le rejet humoral. Néanmoins, leur utilisation en pratique courante est restreinte du fait de leur faible disponibilité, des difficultés à interpréter les données produites, et de leur coût. De plus, du fait de cette sous-utilisation en pratique clinique, leur impact exact dans la prise en charge des patients n’est pas déterminé. Au cours de cette thèse, un outil de diagnostic moléculaire ayant des caractéristiques compatibles avec une utilisation en pratique clinique a été développé. Celui-ci permet de diagnostiquer le rejet et de le classer en rejet humoral ou cellulaire. Dans un second temps, cet outil a été confronté à des situations cliniques litigieuses, afin d’évaluer son intérêt en pratique courante.À travers ces travaux, cette thèse vise d’une part à améliorer la compréhension de la réponse humorale en transplantation rénale, afin de contribuer à terme à mieux stratifier le risque immunologique en transplantation, et d’autre part à améliorer les modalités diagnostiques du rejet en aidant à la généralisation des outils de biologie moléculaire appliqués aux biopsies de greffons rénaux
Kidney transplantation is the best treatment of end-stage renal disease, improving life quality and quantity. Despite advances in pathophysiological knowledge of kidney transplant immunology, kidney transplant rejection remains the major cause of allograft dysfunction, especially antibody-mediated rejection.Antibody-mediated rejection risk assessment is based on the evaluation of donor-specific anti-HLA antibodies. However, these antibodies have a poor predictive value for incidence and prognosis of rejection. This could be explained by the heterogeneity of their intrinsic characteristics. These characteristics depend on cells responsible for their secretion, which include short- and long- lived plasma cells. Consequently, they indirectly depend on the cells responsible for maintaining the pool of these antibody-secreting cells, such as memory B cells. In infectious diseases, it is known that memory B cells are heterogeneous in terms of phenotype, function, degree of clonality, and diversification of their B-cell receptor (BCR). However, this heterogeneity has not been examined in the context of kidney transplantation.The aim of the first part of this thesis was to study the heterogeneity of HLA-specific memory B cells in sensitised patients on kidney transplant waiting list. To this end, single-cell analysis of HLA-specific memory B cells from patients with various aetiologies and degrees of immunisation was performed. This led to their phenotypic and transcriptomic characterisation and to the assessment of their BCR repertoire.The second part of this thesis was dedicated to the diagnosis of kidney transplant rejection.In recent years, biopsy-based transcriptomics has emerged, enabling the assessment of hundreds of transcripts in kidney biopsy tissue. These tools provide the opportunity to elucidate new physiopathological pathways and potentially enhance the diagnosis of rejection, especially humoral rejection. However, their application in clinical practice is still limited due to their restricted availability, required expertise for data processing and interpretation, and cost. Furthermore, their exact impact on patient management remains undetermined. Here, a molecular diagnostic tool with characteristics suitable for clinical use was developed. This tool enables the diagnosis of rejection and its classification between antibody-mediated and T-cell mediated rejection. Subsequently, this tool was assessed in ambiguous clinical situations to evaluate its impact in clinical practice.Through these studies, this thesis focused on enhancing our understanding of the humoral response in renal transplantation, which could help improving immunological risk stratification in transplantation. Additionally, it aimed to improve biopsy-based transcriptomics in the diagnosis of kidney transplant rejection