The 16A1 monoclonal antibody recognizes human CD140a also known as the platelet-derived growth factor receptor, alpha polypeptide, PDGFR2, and PDGFRalpha. CD140a is a cell surface tyrosine kinase receptor for members of the platelet-derived growth factor family. The identity of the growth factor bound to the receptor determines whether the functional receptor is a homodimer or heterodimer composed of both PDGFR-alpha and -beta. CD140a contains three immunoglobulin-like domains and a tyrosine kinase domain with a predicted molecular weight approximately 123 kD. CD140a is widely expressed on a variety of mesenchymal-derived cells and has been implicated in the development of some tumors including basal cell carcinoma and gastric stromal cell tumors. Binding of A-chain containing PDGF molecules as well as protease-activated PDGF-C molecules can stimulate cell proliferation. CD140a has been shown to interact with a number of proteins including CRK, Grb2, Grb14, SHP2, and others as integrin beta3, caveolin-1, and nexin sorting molecules. The PDGFRalpha is heavily phosphorylated on numerous tyrosine residues through both autophosphorylation and ligand-dependent processes. The 16A1 antibody has been shown to be useful for flow cytometric detection of CD140a.