CD274 and neoplasm: PD-1 interaction with its ligand, PD-L1, aberrantly expressed on tumor cells, results in T cell inactivation and apoptosis and inhibited activation of tumor antigen-specific T cells (Rosenblatt et al., 2012) by reducing the production of IL-2, IFN-γ, and stimulating IL-10 production (Ge et al., 2013).