PDCD1 and neoplasm: T cells have been successfully used for immunotherapy in a number of ways, including immune checkpoint blockade, which uses monoclonal antibodies to bind and inactivate inhibitory receptors such as cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) and programmed cell death-1 (PD-1) or its ligand programmed cell death ligand 1 (PD-L1) (101), or adoptive cell transfer, which involves the isolation of T cells, improving their anti-tumor capacity in vitro, expanding them in culture, and transferring them back to the patient (102).