PDCD1 and infection: To identify factors that promote the self-renewal and multipotency of TPEX cells, we performed single-cell RNA sequencing (scRNA-seq) of TPEX-cell-enriched (PD-1+TIM-3−) CD8+ T cells sorted at 30 days post-infection (dpi) from mice chronically infected with lymphocytic choriomeningitis virus (LCMV) clone-13 (Cl13).