CTLA4 and neoplasm: Mechanistically, immunoinhibitors such as cytotoxic T lymphocyte-associated molecule-4 (CTLA-4), programmed cell death receptor-1 (PD-1), and PD ligand-1 (PD-L1) act as direct negative regulators of effector cytotoxic cells, inducing immune tolerance and inhibiting anti-tumor immune responses [131, 132].