T_reg cell tune-up

Sci. Immunol. https://doi.org/10.1126/sciimmunol.aat6975 (2018)

The microbiota exerts profound effects on the development and responses of the gut immune system. In Science Immunology, Im and colleagues screen many microbiotal strains for their ability to generate regulatory T cells (T_reg cells) de novo. One strain of Bifidobacterium bifidum strongly induces T_reg cells mainly in the colon lamina propria. Mechanistically, a neutral polysaccharide extract (CSGG) of B. bifidum converts dendritic cells into a regulatory form, largely by binding and signaling via the receptor TLR2. These regulatory dendritic cells then use the immunomodulatory cytokine TGF-β to convert conventional T cells into T_reg cells that are able to suppress a model of colitis. These findings shed light on the mechanism by which the microbiota can modulate gut immune responses.