FCER1: Difference between revisions

The '''high-affinity IgE receptor''', also known as '''FcεRI''', or '''Fc epsilon RI''', is the high-[[Affinity (pharmacology)|affinity]] [[receptor (biochemistry)|receptor]] for the [[Fc region]] of [[immunoglobulin E]] (IgE), an [[antibody]] [[Isotype (immunology)|isotype]] involved in the [[allergy]] disorderdisorders and [[parasitism|parasitesparasite]] immunity. FcεRI is a [[tetrameric protein|tetramer]]ic receptor complex that binds Fc portion of the ε [[Immunoglobulin heavy chain|heavy chain]] of [[IgE]].<ref>{{Cite book|url=https://www.amazon.com/Robbins-Basic-Pathology-ebook/dp/B007OMFA6Q/ref=mt_kindle?_encoding=UTF8&me=|title=Robbins Basic Pathology|lastlast1=Kumar|firstfirst1=Vinay|last2=Abbas|first2=Abul K.|last3=Aster|first3=Jon|date=2012-05-01|publisher=Saunders|edition=9|language=en}}</ref> It consists of one alpha ([[FCER1A|FcεRIα]] -– antibody binding site), one beta ([[FCER1B|FcεRIβ]] -– which amplifies the downstream signal), and two gamma chains ([[FCER1G|FcεRIγ]] -– the site where the downstream signal initiates) connected by two disulfide bridges on [[Mast cell|mast cells]] and [[Basophil|basophils]]. It lacks the beta subunit on other cells. It is constitutively expressed on [[mast cells]] and [[basophils]]<ref name="pmid11964662">{{cite journal | author = Pawankar R | title = Mast cells as orchestrators of the allergic reaction: the IgE-IgE receptor mast cell network | journal = Current Opinion in Allergy and Clinical Immunology | volume = 1 | issue = 1 | pages = 3–6 |date=February 2001 | pmid = 11964662 | doi = 10.1097/00130832-200102000-00002}}</ref> and is inducible in [[Eosinophil|eosinophils]].

FcεRI is found on epidermal [[Langerhans cell]]s, eosinophils, mast cells, and basophils.<ref>{{cite journal |vauthors=Ochiai K, Wang B, Rieger A, Kilgus O, Maurer D, Födinger D, Kinet J, Stingl G, Tomioka H |title=A review on Fc epsilon RI on human epidermal Langerhans cells |series=104 |journal=International Archives of Allergy and Immunology |volume=Suppl 1 |issue=1 |pages=63–64 |year=1994 |pmid=8156009 |doi=10.1159/000236756}}</ref><ref>{{cite journal |vauthors=Prussin C, Metcalfe D |title=5 |journal=Nature |year=1994 |volume=367 |issue=6459 |pages=183–6 |pmid=8114916 |doi=10.1038/367183a0|s2cid=4331405 }}</ref><ref>{{cite journal |last1=Gounni |first1=A. |last2=Lamkhioued |first2=B. |last3=Ochiai |first3=K. |last4=Tanaka |first4=Y. |last5=Delaporte |first5=E. |last6=Capron |first6=A. |last7=Kinet |first7=J.P. |last8=Capron |first8=M. |title=IgE, mast cells, basophils, and eosinophils |journal=Journal of Allergy and Clinical Immunology |volume=117 |issue=2 Suppl Mini–Primer |pages=S450–5456 |year=2006 |pmid=16455345 |doi=10.1016/j.jaci.2005.11.016}}</ref> As a result of its cellular distribution, this receptor plays a major role in controlling [[allergy|allergic responses]]. FcεRI is also expressed on [[antigen-presenting cell]]s, and controls the production of important immune mediators ([[cytokine]]s, [[interleukin]]s, [[leukotriene]]s, and [[prostaglandin]]s) that promote [[inflammation]].<ref>{{cite journal |vauthors=von Bubnoff D, Novak N, Kraft S, Bieber T |title=The central role of FcepsilonRI in allergy |journal=Clinical and Experimental Dermatology |volume=28 |issue=2 |pages=184–187 |year=2003 |pmid=12653710 |doi=10.1046/j.1365-2230.2003.01209.x|s2cid=2080598 }}</ref> The most known mediator is [[histamine]], which results in the five symptoms of inflammation: heat, swelling, pain, redness and loss of function.

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 [[Muscle_cell#Smooth_muscle_cells|smooth muscle cell]])-mediated link to airway inflammation and AHR[[airway hyperresponsiveness]].<ref>{{cite journal|lastlast1=Gounni|firstfirst1=A.S.|last2=Wellemans|first2=V.|last3=Yang|first3=J.|last4=Bellesort|first4=F.|last5=Kassiri|first5=K.|last6=Gangloff|first6=S.|last7=Guenounou|first7=M.|last8=Halayko|first8=A.J.|last9=Hamid|first9=Q.|last10=Lamkhioued|first10=B.|authorlink8=Andrew Halayko|title=Human airway smooth muscle cells express the high affinity receptor for IgE (Fc epsilon RI): a critical role of Fc epsilon RI in human airway smooth muscle cell function|url=https://www.jimmunol.org/content/175/4/2613|journal=Journal of Immunology|volume=175|issue=4|pages=2613–2621|date=August 15, 2005|pmid=16081836|doi=10.4049/jimmunol.175.4.2613|doi-access=free}}</ref><ref>{{cite journal|last=Gounni|first=A.S.|title=The high-affinity IgE receptor (FcepsilonRI): a critical regulator of airway smooth muscle cells?|url=https://journals.physiology.org/doi/full/10.1152/ajplung.00005.2006|journal=American Journal of Physiology| date=September 2006|volume=291|issue=3|pages=L312-321|pmid=16581830|doi=10.1152/ajplung.00005.2006}}</ref>

Crosslinking of the FcεRI via IgE-[[antigen]] complexes leads to degranulation of mast cells or basophils and release of [[inflammation|inflammatory]] mediators.<ref name="pmid14630197">{{cite journal | author = Siraganian RP | title = Mast cell signal transduction from the high-affinity IgE receptor | journal = Current Opinion in Immunology | volume = 15 | issue = 6 | pages = 639–646 |date=December 2003 | pmid = 14630197 | doi = 10.1016/j.coi.2003.09.010 | urls2cid = 39294873 | url = https://zenodo.org/record/1258843}}</ref> 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.<ref name="pmid16272313">{{cite journal |vauthors=Bobrzynski T, Fux M, Vogel M, Stadler MB, Stadler BM, Miescher SM | title = A high-affinity natural autoantibody from human cord blood defines a physiologically relevant epitope on the FcepsilonRIalpha | journal = Journal of Immunology | volume = 175 | issue = 10 | pages = 6589–6596 |date=November 2005 | pmid = 16272313 | doi = 10.4049/jimmunol.175.10.6589| doi-access = free }}</ref>