However, their location in close contact with tumor cells, their ability to proliferate in situ, to produce granzyme B and other cytotoxic molecules and pro-inflammatory cytokines, support the hypothesis that TRM cells are enriched in tumor-specific CD8+ T cells that could trigger specific cytotoxic activity toward target cells in physiological conditions and following neutralization of PD-1–PD-L1 interaction, as we demonstrated ex vivo (15) and possibly also during anti-PD-1/anti-PD-L1 cancer immunotherapy. The gene discussed is PDCD1; the disease is cancer.