IL3RA(INTERLEUKIN 3 RECEPTOR, ALPHA), also called CD123 (Cluster of Differentiation 123), is a human gene. The protein encoded by this gene is an interleukin 3 specific subunit of a heterodimeric cytokine receptor which is composed of a ligand specific alpha subunit and a signal transducing beta subunit shared by the receptors for interleukin 3 (IL3), colony stimulating factor 2 (CSF2/GM-CSF), and interleukin 5 (IL5).The IL3RA is mapped on Xp22.33. The genomic structures of IL3RA and CSF2RA are very similar and share an additional exon encoding part of the C-terminal domain not found in other members of this gene family. As in human hematopoietic cells, IL3 and GMCSF competed for binding in fibroblasts expressing the cDNAs for IL3RA, CSF2RA, and the common beta subunit, indicating that different alpha subunits compete for a common beta subunit.