With these immunosuppressive environments, inhibitory receptors including programmed cell death protein 1 (PD-1), cytotoxic T lymphocyte-associated protein 4 (CTLA-4), and lymphocyte activation gene (LAG-3) are upregulated in tumor cells and APCs to further inhibit the T cell effector functions [6,85]. The gene discussed is PDCD1; the disease is neoplasm.