Human secreted Programmed Cell Death 1 Ligand 1 (PD-L1)-Fc fusion protein, also known as CD274 and B7 homolog 1 (B7-H1) with a K124A mutation,GenBank Accession No. NM_014143,amino acids 19-239, fused at the Cterminus with the Fc portion of human IgG1,with C-terminal Avitag™ expressed in a HEK293 cell expression system and enzymatically biotin-labeled using Avitag™ technology. MW = 54 kDa.