These CD8+PD-1+TCF-1+ T cells expand and differentiate into terminally exhausted CD8+ T cells (CD8+PD-1+TCF-1- T cells) with increased cytotoxicity but are short-lived in the tumor microenvironment in response to anti-PD-1 antibody treatment9,13,14. The gene discussed is PDCD1; the disease is neoplasm.