Introduction: Signals delivered by serum monomeric IgA (mIgA) are essential in controlling the immune system by preventing the development of autoimmunity and inflammation. However, IgA can also, when aggregated, be deleterious to the host, inducing inflammatory diseases. This Janus-like nature of IgA is mainly due to their heterogeneity in molecular forms and their interaction with IgA receptors.
Discussion: While serum mIgA are mainly involved in FcalphaRI-mediated inhibition of immune responses, macromolecular serum IgA or circulating IgA immune complexes are often deleterious to the host by inducing sustained activation through IgA receptors including FcalphaRI and transferrin receptor.
Conclusion: FcalphaRI-mediated inhibitory function is able to suppress several inflammatory diseases in mice including asthma and glomerulonephritis. Intravenous mIgA (mIgAIV) and anti-FcalphaR monovalent antibodies represent thus promising tools for immunotherapy.