CD300a

CD300a (also IRp60, CMRF-35H9) is an inhibitory immunoreceptor of the CD300 family, a group of immunoglobulin superfamily molecules with a single V-set Ig-like ectodomain recognizing lipids. CD300a is a type I transmembrane glycoprotein whose cytoplasmic tail contains four ITIM (immunoreceptor tyrosine-based inhibition motif) sequences, the highest density among immune receptors, which upon phosphorylation recruit SHP-1, SHP-2 and SHIP to dampen activating signals. CD300a is broadly expressed on myeloid and lymphoid cells-neutrophils, monocytes, macrophages, mast cells, eosinophils, NK cells, and B and T cell subsets. Its ligands include phosphatidylserine (exposed on apoptotic cells and enveloped viruses) and phosphatidylethanolamine and phosphatidylcholine moieties on oxidized LDL and viral particles. CD300a engagement suppresses FcεRI-mediated mast cell degranulation, IgE-dependent anaphylaxis, eosinophil activation, NK cytotoxicity and TLR-driven inflammation, and facilitates the phagocytosis of apoptotic cells, positioning CD300a as a therapeutic candidate in allergy, asthma, viral infection and autoinflammation.