These two ligands, PD-L1 (B7-H1) and PD-L2 (B7-DC), expressed mainly in the placenta, tonsil, and retina, both belong to the B7 family of cell surface glycoproteins (30).PD-L1 is expressed in non-hematopoietic cells such as endothelial, epithelial, and tumor cells and appears in dendritic cells, myeloid cells, T and B cells, and other hematopoietic cells (31). This evidence concerns the gene CD274 and neoplasm.