The high-affinity IgE receptor, also known as FcεRI, or Fc epsilon RI, is the high-affinityreceptor for the Fc region of immunoglobulin E (IgE), an antibodyisotype involved in allergy disorders and parasite immunity. FcεRI is a tetrameric receptor complex that binds Fc portion of the ε heavy chain of IgE.[1] It consists of one alpha (FcεRIα – antibody binding site), one beta (FcεRIβ – which amplifies the downstream signal), and two gamma chains (FcεRIγ – the site where the downstream signal initiates) connected by two disulfide bridges on mast cells and basophils. It lacks the beta subunit on other cells. It is constitutively expressed on mast cells and basophils[2] and is inducible in eosinophils.
The structure of the FcεRI receptorSummary of IgE/FcεRI receptor mediated downward signal cascade
FcεRI was demonstrated in bronchial/tracheal airway smooth muscle cells in normal and asthmatic patients. FcεRI cross-linking by IgE and anti-IgE antibodies led to Th2 (IL-4, -5, and -13) cytokines and CCL11/eotaxin-1 chemokine release; and ([Ca2+]i) mobilization, suggesting a likely IgE-FcεRI-ASM (airway smooth muscle cell)-mediated link to airway inflammation and airway hyperresponsiveness.[7][8]
Mechanism of action
Crosslinking of the FcεRI via IgE-antigen complexes leads to degranulation of mast cells or basophils and release of inflammatory mediators.[9] Under 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.[10]
^Kumar, Vinay; Abbas, Abul K.; Aster, Jon (2012-05-01). Robbins Basic Pathology (9 ed.). Saunders.
^Pawankar R (February 2001). "Mast cells as orchestrators of the allergic reaction: the IgE-IgE receptor mast cell network". Current Opinion in Allergy and Clinical Immunology. 1 (1): 3–6. doi:10.1097/00130832-200102000-00002. PMID11964662.
^Ochiai K, Wang B, Rieger A, Kilgus O, Maurer D, Födinger D, Kinet J, Stingl G, Tomioka H (1994). "A review on Fc epsilon RI on human epidermal Langerhans cells". International Archives of Allergy and Immunology. 104. Suppl 1 (1): 63–64. doi:10.1159/000236756. PMID8156009.
