IL5 Receptor alpha antibody

Interleukin 5 (IL5), produced primarily by activated T lymphocytes and mast cells, has diverse biological effects on a variety of cell types. IL5 is a potent eosinophil differentiation and activation factor in vivo and in vitro. It also stimulates the proliferation and/or differentiation of basophils and B cells. The effects of IL5 are mediated by binding of the cytokine to specific cell surface receptors expressed on target cells. The high-affinity receptor complex for IL5 consists of a cytokine specific ligand binding alpha chain and a signaling beta chain that can modulate the ligand binding affinity of the receptor complex. The beta chain is shared with the high affinity receptor complexes for IL3 and GMCSF. Alone, the beta chain does not bind cytokines but is needed for cytokine-mediated signaling. Human and mouse cDNA clones for the alpha chain of the high affinity IL5 receptor (IL5RA) complexes have been isolated. The 315 amino acid residue recombinant human IL5RA has a predicted molecular mass of approximately 38 kDa. Due to glycosylation, the recombinant protein migrates as a 43 kDa band in SDS-PAGE. Human and mouse IL5RA are members of the hematopoietin receptor superfamily characterized by the presence of the WSXWS, and a four cysteine residue motif in the extracellular domain of the transmembrane protein. In addition to the cDNA clone encoding the full-length transmembrane protein, cDNA clones (arising from alternative splicing and encoding soluble secreted forms of IL5RA) have been isolated from mouse as well as human cells. A naturally occurring soluble form of the IL5RA has been detected in biological fluids of autoimmune-prone mice and mice bearing chronic B cell leukemia. Recombinant human IL5RA binds human IL5 in a 1:1 ratio and acts as a human IL5 antagonist. The molecule inhibits the proliferation of IL5 dependent cell lines and blocks human umbilical cord blood eosinophil differentiation.