Following TCR activation in context of chronic infection or cancer, inhibitory receptors (IRs) such as programmed cell death protein 1 (PD-1), lymphocyte activation gene 3 (LAG-3), cytotoxic T lymphocyte-associated protein 4 (CTLA-4) T cell immunoglobulin and mucin domain-containing protein 3 (TIM3) and CD101 are upregulated [18,19]. This evidence concerns the gene PDCD1 and cancer.