Human secreted Programmed Cell Death 1 (PD-1)-Fc fusion protein, also known as CD279, PDCD1, and SLEB2, GenBank Accession No. NM_005018, amino acids 25-167 with an I126A mutation, fused at the C-terminus with the Fc portion of human IgG1, and C-terminal AviTag™, expressed in a HEK293 cell expression system and enzymatically biotin-labeled using AviTag™ technology. MW = 44.5 kDa. This protein runs at a higher MW by SDS-PAGE due to glycosylation.