PD-1/PD-L1 checkpoint-blocking antibodies are thought to act primarily in the tumor microenvironment, where PD-L1 is expressed by tumor cells (174), myeloid cells (168, 203, 204), LECs (94, 95, 98), blood endothelial cells (95), B cells (205, 206), T cells (207), dendritic cells (30, 203) and NK cells (208, 209). The gene discussed is CD274; the disease is neoplasm.