Single-cell RNA sequencing reveals peripheral blood mononuclear immune cell landscape associated with operational tolerance in a kidney transplant recipient [2]
Operational tolerance (OT) after kidney transplantation is defined as stable graft acceptance without the need for immunosuppression therapy. However, it is not clear which cellular and molecular pathways are driving tolerance in these patients.  In this first-of-its-kind pilot study, we assessed the immune landscape associated with OT (Tol) using the single-cell analyses. Peripheral mononuclear cells (PBMCs) from a kidney transplant recipient (KTR) with OT, a healthy individual (HC), and a KTR with normal kidney function standard of care immunosuppression (SOC) were evaluated. B cell proportion was greatest in Tol with the predominance of TCL1A+ naïve B cells; regulatory T cell (Tregs) was also high in Tol with a relatively higher expression of LSGAL1.  Putative ligand-receptor-based cell-cell interactions between B cells and Tregs were identified. TGFB-TGFBR interaction, present in both Tol and SOC, leads to the proliferation of Tregs. However, SOC had the lowest proportion of B cells and Tregs with a G1 phase accumulation of B and T cells. Our findings instigate application of this technology on a larger cohort to identify mediators of tolerance. Overall design: PBMCs were isolated from a healthy control, a KTR with stable graft function and on standard of care, and a KTR who attained operational tolerance case (n=1).  Single cell RNA sequencing was done on this PBMCs. The proportion of cells and the differences in their gene expression was analysed and compared across the three groups to identify molecular and cellular landscape associated with operational tolerance.