CD123 is the 70 kDa transmembrane alpha chain of the interleukin-3 (IL-3) receptor. It binds IL-3 with low affinity when alone; however, upon association with CD131 (the common beta chain), the complex binds IL-3 with high affinity. CD123 does not transduce intracellular signals upon IL-3 binding and requires the beta chain for this function. CD123 is expressed on bone marrow precursor cells, macrophages, dendritic cells, mast cells, basophils, megakaryocytes, and certain B-cell populations.
