High dimensional profiling of immune responses to kidney transplant reveals heterogeneous T helper 1 and B cell effectors associated with rejection.

Rejection is a primary cause of allograft dysfunction after kidney transplantation. 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 state from rejection. Patients undergoing T-cell mediated rejection displayed accumulation of clonally expanded of cytotoxic T helper (Th)1 cells and of 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 (Tfh) cells and effector T-bet+ memory B cells, both of which strongly expressed IL-12 and TNF-signaling pathways. Plasma cytokine analysis confirmed mixed Th1/Th17 and Th1/Tfh-driven inflammatory profiles distinguishing T-cell mediated rejection and antibody-mediated rejection, respectively. CD4T and B cell subpopulations and signatures were validated by bulk RNA-seq analysis of matched kidney allografts and using an independent single-cell RNAseq dataset. These data improve mechanistic understanding of immune pathogenesis of rejection and support development of more specific immunosuppressive therapies to treat allograft rejection.