Immune checkpoint inhibitors, such as anti-PD-1, bind to PD-1 receptors expressed on the surface of infiltrating cytotoxic T-lymphocytes (CD8+), B-cells, and natural killer (NK) cells in the tumor microenvironment, which enhances the cytotoxic effects of CD8+ T cells [19,20,21,22]. The gene discussed is CD8A; the disease is neoplasm.