A human high affinity interleukin-5 receptor (IL5R) is composed of an IL5-specific alpha chain and a beta chain shared with the receptor for GM-CSF. 
cDNA clones encoding two receptor proteins involved in the binding of human interleukin 5 (hIL5) have been isolated.  A first class codes for an IL5-specific chain (hIL5R alpha).  The major transcript of this receptor gene, as analyzed in both HL-60 eosinophilic cells and eosinophilic myelocytes grown from cord blood, encodes a secreted form of this receptor.  This soluble hIL5R alpha has antagonistic properties.  A second component of the hIL5R is found to be identical to the beta chain of the human granulocyte-macrophage colony-stimulating factor (GM-CSF) high affinity receptor.  The finding that IL5 and GM-CSF share a receptor subunit provides a molecular basis for the observation that these cytokines can partially interfere with each other's binding and have highly overlapping biological activities on eosinophils.