FcεRI

FcεRI, or Fc epsilon RI, is the high-affinity receptor for immunoglobulin E (IgE), an antibody isotype involved in allergy and resistance to parasites. FcεRI is a tetrameric receptor complex consisting of one alpha (FcεRIα), one beta (FcεRIβ), and two gamma chains (FcεRIγ). It is expressed predominantly on mast cells and basophils.

Crosslinking of the FcεRI via IgE-allergen complexes leads to degranulation of mast cells or basophils and release of inflammatory mediators. At laboratory conditions degranulation of isolated basophils can also be induced with antibodies to the FcεRIα which crosslink the receptor. Such crosslinking and potentially pathogenic autoantibodies to the FcεRIα have been isolated from human cord blood, which suggest that they occur naturally and are present already at birth. However, their epitope on FcεRIα was masked by IgE and the affinity of the corresponding autoantibodies found in healthy adults appeared lowered.