CD274 and neoplasm: The combination of PD-L1 and PD-1 inhibits T cell proliferation, IL-2 and IFN-γ secretion, inhibition of tumor-specific CD8+ T cell cytolytic activity, and induction of cytotoxic T lymphocyte apoptosis, induction and maintenance of T cell inactivation,, thus making TH2 dominant in tumor microenvironment and resulting in tumor immune escape [95].