Although the results are not entirely satisfactory, clinical trials and experimental models are underway to enhance anti-tumor T cell functions with monoclonal antibodies that block the interaction of PD-1 with PD-L1 [57,59] and other molecules that suppress T lymphocyte function, such as CTLA-4 [60] or tumor necrosis factor receptor 2 (TNFR2) [61], which will be reviewed in the following sections. The gene discussed is PDCD1; the disease is neoplasm.