Human secreted Programmed Cell Death 1 Ligａnd 1 (PD-L1)-Fc fusion protein, also known as CD274 and B7 homolog 1 (B7- H1), GenBank Accession No. NM_014143, amino acids 19-239, fused at the C-terminus to the Fc portion of human IgG1, expressed in a HEK293 cell expression system. MW = 52 kDa.