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IgA and FcαRI: Versatile Players in Homeostasis, Infection, and Autoimmunity

 

Authors van Gool MMJ, van Egmond M

Received 20 October 2020

Accepted for publication 17 December 2020

Published 5 January 2021 Volume 2020:9 Pages 351—372

DOI https://doi.org/10.2147/ITT.S266242

Checked for plagiarism Yes

Review by Single anonymous peer review

Peer reviewer comments 2

Editor who approved publication: Professor Michael Shurin

Abstract: Mucosal surfaces constitute the frontiers of the body and are the biggest barriers of our body for the outside world. Immunoglobulin A (IgA) is the most abundant antibody class present at these sites. It passively contributes to mucosal homeostasis via immune exclusion maintaining a tight balance between tolerating commensals and providing protection against pathogens. Once pathogens have succeeded in invading the epithelial barriers, IgA has an active role in host-pathogen defense by activating myeloid cells through divers receptors, including its Fc receptor, FcαRI (CD89). To evade elimination, several pathogens secrete proteins that interfere with either IgA neutralization or FcαRI-mediated immune responses, emphasizing the importance of IgA-FcαRI interactions in preventing infection. Depending on the IgA form, either anti- or pro-inflammatory responses can be induced. Moreover, the presence of excessive IgA immune complexes can result in continuous FcαRI-mediated activation of myeloid cells, potentially leading to severe tissue damage. On the one hand, enhancing pathogen-specific mucosal and systemic IgA by vaccination may increase protective immunity against infectious diseases. On the other hand, interfering with the IgA-FcαRI axis by monovalent targeting or blocking FcαRI may resolve IgA-induced inflammation and tissue damage. This review describes the multifaceted role of FcαRI as immune regulator between anti- and pro-inflammatory responses of IgA, and addresses potential novel therapeutic strategies that target FcαRI in disease.
Keywords: neutrophil, CD89, mucosa, infection, inflammation, autoimmunity