PRF1 and neoplasm: As the major players in immunotherapy today, cytotoxic CD8+ T cells (CD8+ T cells) undertake cytolytic activities against tumor cells via the following steps: firstly, effector CD8+ T cells are activated upon the recognition of an antigen major histocompatibility complex (MHC) on the tumor cell; then, granules that contain perforin, granzyme, and the Fas ligand are released by CD8+ T cells upon successful recognition to give full rein to effector functions.