Upon administration, the antibody binds to and obstructs the interaction of PD-1 with its ligands, programmed cell death ligand 1 (PD-L1), inhibits the activation of PD-1 and its downstream signaling pathways, and reinstates immune function by activating cytotoxic T lymphocytes and cell-mediated immune responses against tumor cells or pathogens. The gene discussed is PDCD1; the disease is neoplasm.