IgA synthesis: a form of functional immune adaptation extending beyond gut

Immunoglobulin A (IgA) is the most abundantly produced antibody isotype in mammals. The primary function of IgA is to maintain homeostasis at mucosal surfaces. IgA is generated in specialized gut associated lymphoid tissues (GALT) by T cell-dependent and T cell-independent mechanisms. Studies in mice have demonstrated that IgA diversification has an essential role in the regulation of gut microbiota. Aberrant bacterial growth, by activating innate and adaptive immune cells, has emerged as a risk factor for inflammatory diseases such as metabolic disorders and autoimmune diseases. Dynamic diversification of IgA shields bacterial antigens preventing inflammatory responses, but when IgA regulation is suboptimal aberrant bacterial growth and inflammation can ensue. ⺠IgA, by promoting microbial diversity in the gut, is likely to have played a fundamental role in mammalian evolution. ⺠The IgA system fulfils multiple functions in order to maintain homeostasis at mucosal surface. ⺠IgA regulates the intestinal microbiota that is pivotal for efficient immune system and metabolic function. ⺠Defects in IgA regulation have the potential to increase autoimmune susceptibility beyond mucosal surfaces.