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Melissa Maria Johanna van Gool,1,2 Marjolein van Egmond1– 3 1Department of Molecular Cell Biology and Immunology, Amsterdam UMC, Amsterdam, Vrije Universiteit Amsterdam, Amsterdam, Netherlands; 2Amsterdam institute for Infection and Immunity, Amsterdam UMC, Amsterdam, Netherlands; 3Department of Surgery, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, NetherlandsCorrespondence: Marjolein van Egmond Tel +31204448080Email m.vanegmond@amsterdamumc.nlAbstract: 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 |
