Platelet-derived growth factor receptor β (PDGFRB), also known as CD140b, and the structural homologous protein PDGFRA (CD140a) are members of the receptor tyrosine kinase (RTK) Class III subfamily, which also includes receptors for M-CSF, SCF, and Flt-3 ligands. All Class III RTKs contain five immunoglobulin-like domains in the extracellular region and one kinase domain in the intracellular region. PDGF is an important serum mitogen, which can form homologous or heterodimer proteins by connecting PDGF-A and PDGF-B chains via disulfide bonds. PDGFRA and PDGFRB bind the isomers of PDGF-AA, PDGF-BB and PDGF-AB with different affinities, in which PDGFRA can bind the 3 isomers of PDGF with high affinity, while PDGFRB can only bind PDGF-BB with high affinity. PDGF binding can induce homologous and heterodimerization of receptors and signal transduction. PDGFRA and PDGFRB are independently regulated in a variety of cell types. The recombinant soluble PDGFRB can bind PDGF with high affinity and is an effective PDGF antagonist.