Programmed cell death ligand 1 (PD-L1, also known as B7-H1 or CD274) is believed to mediate local immune evasion in many types of cancer by binding to programmed cell death 1 (PD-1), its co-stimulatory receptor on T cells, to induce saturation of activated anti-tumor T cells [1]. The gene discussed is PDCD1; the disease is cancer.