Abstract
Bulk analysis of renal allograft biopsies (rBx) identified RNA transcripts associated with acute cellular rejection (ACR); however, these lacked cellular context critical to mechanistic understanding. We performed combined single cell RNA transcriptomic and TCRα/β sequencing on rBx from patients with ACR under differing immunosuppression (IS): tacrolimus, iscalimab, and belatacept. TCR analysis revealed a highly restricted CD8 (+) T cell clonal expansion (CD8 (EXP) ), independent of HLA mismatch or IS type. Subcloning of TCRα/β cDNAs from CD8 (EXP) into Jurkat76 cells (TCR (-/-) ) conferred alloreactivity by mixed lymphocyte reaction. scRNAseq analysis of CD8 (EXP) revealed effector, memory, and exhausted phenotypes that were influenced by IS type. Successful anti-rejection treatment decreased, but did not eliminate, CD8 (EXP) , while CD8 (EXP) were maintained during treatment-refractory rejection. Finally, most rBx-derived CD8 (EXP) were also observed in matching urine samples. Overall, our data define the clonal CD8 (+) T cell response to ACR, providing novel insights to improve detection, assessment, and treatment of rejection.