The 29E.2A3 antibody reacts with human CD274 which is also known as PD-L1 or B7-H1. CD274 is a type 1 transmembrane glycoprotein and a member of the Ig superfamily. PD-L1 is a ligand for CD279 (PD-1) and plays an important role in regulating immune cell responses. CD274 is expressed on activated monocytes, macrophages, dendritic cells, and T cells.