![]() ![]() Mounting evidence clearly reveals that bacterial species colonizing the gut differ in their ability to stimulate the post-natal maturation of the gut system, with a good example being segmented filamentous bacteria (SFB) which are potent stimuli of IgA responses and strong inducers of Peyer’s patches development. Another important observation showing that intestinal IgA help to shape the intestinal microbiota is the recent finding that cessation of breast-feeding to either formula or food drives the maturation of the infant gut microbiome, indicating that the important amount of IgA secreted in mother’s milk seems to play a central role in the regulation of microbiota composition. Moreover, it was observed that the restoration of normal IgA levels in AID (activation-induced cytidine deaminase) deficient mice, which normally lack IgAs, is sufficient to restore a normal microbiota composition. Microbiota analysis of RAG1 -/- mice (which have no adaptive immune system owing to the lack of V(D)J recombination-activating protein 1 (RAG1)) revealed profound alterations in their microbiota composition. The main observation showing the importance of immunoglobulin in microbiota composition regulation was made with animals lacking such Ig production. IgA population in the gut is central for the selection and the maintenance of the intestinal microbiota. One of the main role played by IgA is the promotion of immune exclusion by entrapping dietary antigens and microorganisms in the mucus, or down-regulating the expression of pro-inflammatory bacterial epitopes on commensal bacteria, such as flagellin. Immunoglobulin A-mediated modulation of the intestinal microbiotaĪ key intestinal strategy to generate immune protection in a non-inflammatory manner is the production of IgA, which is schematically illustrated in Fig. Here, we will discuss recent findings describing how IgAs population has an impact on microbiota diversity, and how they may provide therapeutic insights into diseases associated with dysbiosis. Adaptive immunity in general, and sIgA in particular, is known to play a key role in microbiota composition. Additionally, the mucosal immune system has several means to sample and evaluate potential danger of microbiota-derived antigens, allowing production of specific antibodies to bacterial antigens that might compromise the host. These mechanisms include the presence of multi-layered mucus structures, secretion of anti-microbial peptides and the secretion of sIgA. The gut host defense system comprises an array of mechanisms to keep the microbiota in check, maintaining an orderly beneficial relationship with the intestinal microbiota. This commentary will discuss these important new findings, as well as how future therapies can ultimately benefit from such discovery. A recent study published in Immunity by Fransen and colleagues aimed to mechanistically decipher the interrelationship between sIgA and microbiota diversity/composition. Secretory immunoglobulins A (sIgAs), component of the adaptive immune system, are important player in the protection of epithelium, and are known to have an important impact on the regulation of microbiota composition. As reciprocity, the host immune system plays a central role in shaping the composition and localization of the intestinal microbiota. The microbiota contributes to nutrient absorption and maturation of the immune system. The human gut microbiota composition is determined by a myriad of factors, among them genetic and environmental, including diet and medication. The intestinal microbiota is a large and diverse microbial community that inhabits the intestine, containing about 100 trillion bacteria of 500-1000 distinct species that, collectively, provide benefits to the host. ![]()
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