Intestinal microbiota and their metabolites can regulate both local and systemic immunity. In Cell Host and Microbe, Kim and colleagues find that short-chain fatty acids (SCFAs) produced by bacterial fermentation of dietary fiber modulate the production of immunoglobulin A (IgA) in the gut. Mice fed low-fiber diets generate fewer IgA+ B cells and IgA-producing plasma cells in a microbiota-dependent manner. Administration of SCFAs themselves produces a similar effect through an increase in IgA production and directly skews the B cell transcriptional program toward antibody production, probably through the deacetylase-inhibitory activity of SCFAs. Another important function of the SCFAs is their help in driving the metabolically demanding activity of class switching and antibody synthesis by boosting B cell glycolysis. A diet rich in fiber and SCFAs helps to support an effective IgA-mediated response to the gut pathogen Citrobacter rodentium.

Cell Host Microbe 20, 202–214 (2016)