Fc epsilon RI

Fc epsilon RI (FcεRI) is high affinity IgE receptor that binds to the Fc portion of IgE with an affinity of 1010 M−1. It is a heteromultimeric complex that is multiple strands of immunological recognition receptors. It exists in the form of an αβγ2 tetramer or an αγ2 trimer. Allergen-mediated crosslinking of IgE-FcεRI complexes on the surface of blood and tissue cells then triggers the allergic cascade via the receptor’s signaling subunits, FcεRIβ and FcεRIγ. FcεRI has been detected on human mast cells, basophils, neutrophils, monocytes, macrophages, dendritic cells, Langerhans cells, eosinophils and platelets. While the extracellular domain of the receptor α-chain carries the IgE binding site, the β- and γ-chains are involved in signal transduction. The αβγ2 tetramer is expressed in effector cells such as mast cells and basophils, and ligand-engagement leads to cell activation by a defined signaling cascade. In contrast, the αγ2 trimer participates in antigen presentation.