The long-term stability of renal grafts depends on the absence of chronic rejection. As T cells play a key role in rejection processes, analyzing the T-cell repertoire may be useful for understanding graft function outcomes. We have therefore investigated the power of a new statistical tool, used to analyze the peripheral blood TCR repertoire, for determining immunological differences in a group of 229 stable renal transplant patients undergoing immunosuppression. Despite selecting the patients according to stringent criteria, the patients displayed heterogeneous T-cell repertoire usage, ranging from unbiased to highly selected TCR repertoires; a skewed TCR repertoire correlating with an increase in the CD8 1 /CD4 1 T-cell ratio. T-cell repertoire patterns were compared in patients with clinically opposing outcomes i.e. stable drug-free operationally tolerant recipients and patients with the ''suspicious'' form of humoral chronic rejection and were found significantly different, from polyclonal to highly selected TCR repertoires, respectively. Moreover, a selected TCR repertoire was found to positively correlate with the Banff score grade. Collectively, these data suggest that TCR repertoire categorization might be included in the calculation of a composite score for the follow-up of patients after kidney transplantation.
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IntroductionTo prevent graft rejection following kidney transplantation, recipients take lifelong immunosuppression. Despite continuous improvements in such treatments, the half-life of a kidney graft has not increased significantly in the past two decades [1]. Manifest by a decrease in renal function that is associated with specific histological lesions [2], chronic rejection remains the major problem of late allograft loss [3]. The identification of biomarkers predictive of chronic rejection in patients with a stable graft function would therefore be a valuable tool in patient management [4][5][6]. In contrast to the patients who develop chronic rejection, rare cases exist of kidney recipients who tolerate their graft despite discontinuation of immunosuppression [7].Operational tolerance and suspicious chronic Ab-mediated rejection are clinical and immunological situations, representing the two opposing endpoints for patients with stable kidney graft function. Indeed, because T cells have been shown to be involved in both chronic rejection and tolerance [8], we have explored the T-cell repertoire in a cohort of patients with stable kidney graft function. We have previously shown, in a small cohort of patients, that both drug-free operationally tolerant patients (TOL patients) and patients with the ''suspicious'' form of chronic rejection (CHR patients) display a TCR repertoire that differs from healthy, nontransplanted individuals [9][10][11]. In this article, we revisit the relationship between peripheral T-cell repertoire and clinical status, using a new statistical method to analyze the TCR repertoires presented as TcLandscape (TcL) data. We show that, despite being selected accordin...