PRF1 and neoplasm: We have learned from studies of CD8+T cells isolated from progressive tumors that CD8+T cell dysfunction includes tumor-infiltrating lymphocytes (TIL) expressing a variety of inhibitory receptors (such as PD1, LAG3, CTLA4, and TIM3),Reduced or non-production of cytokines (such as interferon-gamma and TNF) or cytotoxic molecules (such as granulozyme and perforin) [46–48].