[Microbiota and IgA response homeostasis]

Mucosal immunity has to deal with a patchy mix of commensal but also eventually pathogenic bugs. Immunoglobulins of the A class (IgA) are opposing to this duality a functional balance going from tolerance to protective response or even to hyper-inflammation. Recent reports have shown the binding of polyreactive natural IgA, but also of affinity maturated protective IgA to the commensal microbiota, to superantigens and also to vaccinal antigens. Diverse types of humoral responses thus altogether contribute to the homeostasis of mucosal immunity. Their knowledge has to be taken into consideration for defining strategies of immuno-intervention, for mucosal vaccination as much as for immunotherapy of chronic inflammatory bowel disease.