PDCD1 and neoplasm: The various forms of immunotherapy include immune checkpoint inhibitors (ICIs)—such as programmed cell death protein 1 (PD-1), programmed cell death ligand 1 (PD-L1), and cytotoxic T-lymphocyte–associated antigen 4 (CTLA-4) inhibitors—, adoptive cell therapies—such as chimeric antigen receptor T-cell therapy, tumor-infiltrating lymphocyte therapy, and natural killer (NK) cell therapy—, cancer vaccines, and cytokine therapies (2).