Interleukin-3 receptor subunit alpha (IL-3RA) or CD123 is a high-affinity receptor for interleukin-3 (IL-3), which along with the primary signaling common Beta (Beta c) subunit (CD131) forms a heterodimer, enabling cell signaling. IL-3RA chain is a glycoprotein of 360 amino acidic residues, composed by an extracellular domain of 287 amino acid residues, involving a predicted Ig-like domain, two Fn III domains, a transmembrane domain of 30 amino acid residues and by an intracellular domain of 53 residues. It is expressed on the majority of CD34+ hemopoietic progenitors and its expression is rapidly lost during erythroid and megakaryocytic differentiation, moderately decreased during monocytic differentiation and is sustained in the granulocytic lineage. IL-3RA is also expressed in a variety of hematological neoplasms including blastic plasmacytoid dendritic cell neoplasm (BPDCN), acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL), chronic myeloid leukemia (CML), Hodgkin&rsquo,s lymphoma and hairy cell leukemia.