Nevertheless, tumor-infiltrating T lymphocytes or tumor-specific T lymphocytes in close proximity to tumor, are found to be exhausted and display an over-expression of several immune checkpoint inhibitors (ICIs) in which programmed cell death protein 1 (PD-1), cytotoxic T-lymphocyte-associated protein-4 (CTLA-4), T-cell immunoglobulin and mucin-domain containing-3 (TIM-3), V-domain Ig suppressor of T cell activation (VISTA) and lymphocyte activating 3 (LAG3) are frequently studied (17, 18). The gene discussed is PDCD1; the disease is neoplasm.