Low dietary fiber intake impairs small intestinal Th17 and intraepithelial T cell development over generations.

Dietary fiber strongly impacts the microbiota. Here, we show that a low-fiber diet changes the small intestinal (SI) microbiota and impairs SI Th17, TCRαß+CD8αß+ and TCRαß+CD8αα+ intraepithelial T cell development. We restore T cell development with dietary fiber supplementation, but this defect becomes persistent over generations with constant low-fiber diets. Offspring of low-fiber diet-fed mice have reduced SI T cells even after receiving a fiber-rich diet due to loss of bacteria important for T cell development. In these mice, only a microbiota transplant from a fiber-rich diet-fed mouse and a fiber-rich diet can restore T cell development. Low-fiber diets reduce segmented filamentous bacteria (SFB) abundance, impairing its vertical transmission. SFB colonization and a fiber-rich diet partially restore T cell development. Finally, we observe that low-fiber diet-induced T cell defects render mice more susceptible to Citrobacter rodentium infection. Together, these results demonstrate the importance of fiber to microbiota vertical transmission and host immune system development.

Microbial Cgr2 will let your Th17 cells ROR(γT).

In this issue of Cell Host & Microbe, Alexander et al. show that the enzyme cardiac glycoside reductase 2 (cgr2), which is produced by Eggerthella lenta, metabolizes RORγT inhibitors, resulting in an increased Th17 response and more severe inflammation in colitis models. The effect of cgr2 can be neutralized by a diet rich in arginine.