Platelet-Derived Growth Factor Receptor β (PDGFR-β) is a member of the protein kinase superfamily and CSF-1/PDGF receptor subfamily. The PDGF family consists of PDGF-A, -B, -C and -D, which form either homo- or heterodimers (PDGF-AA, -AB, -BB, -CC, -DD). The four PDGFs are inactive in their monomeric forms. The PDGFs bind to the protein tyrosine kinase receptors PDGF receptor-α and -β. These two receptor isoforms dimerize upon binding the PDGF dimer, leading to three possible receptor combinations, namely -αα, -ββ and -αβ. The extracellular region of the PDGF receptor-β consists of five immunoglobulin-like domains while the intracellular part is a tyrosine kinase domain. In addition to being a potent mitogen for cells of mesenchymal origin, PDGF has also been shown to be a potent chemoattractant for mesenchymal cells, mononuclear cells, and neutrophils and has been reported to be important in the modification of cellular matrix constituents.