Abstract
Rejection is a primary cause of allograft dysfunction after kidney transplantation. The diversity of immune subpopulations involved in the different endotypes of rejection remains to be delineated at single-cell resolution. In a cohort of 76 kidney transplant recipients, we conducted high-dimensional immune phenotyping of blood CD4 T and B cells, single-cell RNA and T/B cell receptor sequencing, and plasma cytokine profiling. Phenotypic, transcriptional, and clonal states of CD4T and B cells could significantly distinguish stable allograft states from rejection. Patients undergoing T cell-mediated rejection displayed accumulation of clonally expanded cytotoxic T helper (Th)1 cells and Th17-like cells, associated with predominant naive B cell responses. In contrast, antibody-mediated rejection was characterized by clonal expansion of Th1-polarized T follicular helper cells and effector T-bet+ memory B cells, both of which strongly expressed interleukin 12 and tumor necrosis factor-signaling pathways. Plasma cytokine analysis confirmed mixed Th1/Th17 and Th1/T follicular helper cell-driven inflammatory profiles distinguishing T cell-mediated rejection and antibody-mediated rejection, respectively. CD4T and B cell subpopulations and signatures were validated using bulk RNA-seq analysis of matched kidney allografts and using an independent single-cell RNA-seq data set. These data improve mechanistic understanding of the immune pathogenesis of rejection and support the development of more specific immunosuppressive therapies to treat allograft rejection.