PDCD1 and cancer: In recent decades, several inhibitory immunoreceptors, such as programmed cell death protein 1 (PD-1; CD279), PD-L1 (CD274; B7-H1), cytotoxic T-lymphocyte associated protein 4 (CTLA-4; CD154), T cell immunoglobulin and mucin domain-containing protein 3 (TIM3), and lymphocyte-activation gene 3 (LAG3; CD223), T-cell immunoreceptor with Ig and ITIM domains (TIGIT), and B and T lymphocyte attenuator (BTLA; CD272), have been identified and are being investigated in relation to cancer (72, 73).