Gut microbiota and IgA in the intestine
New research in Science sheds new light on this hotly debated topic
The human microbiome, and especially the gut microbiome has been strongly linked to immune system development through IgA stimulation. The exact mechanism has been cause for some debate, with one side claiming that IgA binds to many specific elements of individual bacteria in the microbiome, and others claiming that the IgA reacts less selectively to a broad range of bacteria and bacterial components within the gut microbial community. A recent study from the University of Chicago presents compelling evidence that the interaction is not specific but broad. The team lead by Albert Bendalec showed that IgA was produced at low frequencies in B-cells and selected for in the Peyer's patches and were not specific to individual bacterial epitopes. Rather they broadly bound to different components of the gut microbiome at low affinity.
For more info, check out the abstract below or read the full paper here.
Large quantities of immunoglobulin A (IgA) are constitutively secreted by intestinal plasma cells to coat and contain the commensal microbiota, yet the specificity of these antibodies remains elusive. Here, we profiled the reactivities of single murine IgA plasma cells by cloning and characterizing large numbers of monoclonal antibodies. IgAs were not specific to individual bacterial taxa but rather polyreactive, with broad reactivity to a diverse but defined subset of microbiota. These antibodies arose at low frequencies among naïve B cells, and were selected into the IgA repertoire upon recirculation in Peyer’s patches. This selection process occurred independent of microbiota or dietary antigens. Furthermore, while some IgAs acquired somatic mutations, these did not substantially influence their reactivity. These findings reveal an endogenous mechanism driving homeostatic production of polyreactive IgAs with innate specificity to microbiota.
Natural polyreactive IgA antibodies coat the intestinal microbiota
BY JEFFREY J. BUNKER, STEVEN A. ERICKSON, THEODORE M. FLYNN, CAROLE HENRY, JASON C. KOVAL, MARLIES MEISEL, BANA JABRI, DIONYSIOS A. ANTONOPOULOS, PATRICK C. WILSON, ALBERT BENDELAC
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