PDCD1 and neoplasm: PD-1 expression on APCs was shown to suppress both adaptive and innate immune responses by inhibiting inflammatory cytokines, such as IL-12 and TNF-α, while promoting the production of the immunosuppressive cytokine IL-10.[61,62] In contrast, the PD-1/PD-L pathway can prevent immunopathology due to lymphocyte overactivation.[63] In addition to the PD-1/PD-L pathway, B7-H3, which binds to TLT-2 for costimulatory functions, may have another role in inhibitory functions, especially in the tumor microenvironment.