PDCD1 and neoplasm: To be specific, TAMs interact with T cells, suppress phagocytosis and anti-tumor immunity through PD-1 expression, amplify T cell anergy and apoptosis through PD-L1/L2 expression, mediate T cell apoptosis through FasL and TRAIL expression, scavenge aPD-1 antibodies from T cells and transform into M2 phenotype polarization through FcγRI expression.