Programmed cell death 1 (PD-1) is a transmembrane glycoprotein that, when engaged by its ligands (PD-L1 and PD-L2), is expressed by antigen-presenting cells (APC), cancer cells and cancer cell-associated fibroblasts, inhibiting kinases that are involved in T-cell activation [33,36]. The gene discussed is PDCD1LG2; the disease is cancer.