CD274 and neoplasm: This transmembrane protein has two ligands: programmed cell death ligand 1 (PD-L1, CD274), which is present on activated B cells, T cells, monocytes, dendritic cells, vascular endothelial cells, and certain tumor cells; and PD-L2 or CD273, which is expressed on DCs, macrophages, mast cells, and specific B cell populations [72].