TNFRSF9 and neoplasm: Although these molecules regulate the immune response by providing inhibitory signals that prevent excessive T cell activation and autoimmune damage (37, 38), several studies have reported that PD-1+CD8+ T cells retain functional capacity, including the ability to recognize autologous tumor cells, secrete IFN-γ, and upregulate 4-1BB, as well as containing a fraction of tumor neoantigen-specific T cells (39–41).