The APA5 antibody monoclonal antibody specifically binds to the Platelet-Derived Growth Factor (PDGF) Receptor alpha chain (CD140a, PDGFR-a), a receptor tyrosine kinase that is widely expressed on cells of mesenchymal origin in the embryo and adult and on several other cell types during embryonic development, but not on hematopoietic cells. PDGFR-a binds to PDGF A and B chains, in contrast to PDGFR-b, that binds only to the PDGF B chain. Biologically active PDGF is a disulphide-linked dimer, forming the AA, AB, and BB isoforms. Ligand binding to the PDGF Receptor induces the formation of receptor dimers (aa, ab, or bb), autophosphorylation, and internalization. The APA5 antibody has been demonstrated to block binding of PDGF-AA to PDGFR-a-expressing cells in vitro and to block some PDGF-mediated developmental events in vivo. Synonyms: Pdgfra, Pdgfr2, PDGF-R alpha, Platelet derived growth factor receptor alpha