biostudies-literatureRodriguez-Marino NNCATS NIH HHSEMORY UNIVERSITYNIDDK NIH HHSNIAID NIH HHSNIHNIDDKNIGMS NIH HHS1301-1313https://www.ebi.ac.uk/biostudies/studies/S-EPMC11742265biostudies-literatureUnknown17(6)The impact of dietary fiber on intestinal T cell development is poorly understood. Here we show that a low fiber diet reduces MHC-II antigen presentation by small intestinal epithelial cells (IECs) and consequently impairs development of CD4⁺CD8αα⁺ intraepithelial lymphocytes (DP IELs) through changes to the microbiota. Dietary fiber supports colonization by Segmented Filamentous Bacteria (SFB), which induces the secretion of IFNγ by type 1 innate lymphoid cells (ILC1s) that lead to MHC-II upregulation on IECs. IEC MHC-II expression caused either by SFB colonization or exogenous IFNγ administration induced differentiation of DP IELs. Finally, we show that a low fiber diet promotes overgrowth of Bifidobacterium pseudolongum, and that oral administration of B. pseudolonMucosal immunologyDietary fiber promotes antigen presentation on intestinal epithelial cells and development of small intestinal CD4⁺CD8αα⁺ intraepithelial T cells.PMC11742265R01 DK129950UL1 TR002378R35 GM142503T32 AI106699Cervantes-Barragan LScharer CDSeto ERivera-Rodriguez DEJones RMRodriguez-Marino NGracien IRoyer CJGracz ADfalseDietary fiber promotes antigen presentation on intestinal epithelial cells and development of small intestinal CD4⁺CD8αα⁺ intraepithelial T cells.The impact of dietary fiber on intestinal T cell development is poorly understood. Here we show that a low fiber diet reduces MHC-II antigen presentation by small intestinal epithelial cells (IECs) and consequently impairs development of CD4⁺CD8αα⁺ intraepithelial lymphocytes (DP IELs) through changes to the microbiota. Dietary fiber supports colonization by Segmented Filamentous Bacteria (SFB), which induces the secretion of IFNγ by type 1 innate lymphoid cells (ILC1s) that lead to MHC-II upregulation on IECs. IEC MHC-II expression caused either by SFB colonization or exogenous IFNγ administration induced differentiation of DP IELs. Finally, we show that a low fiber diet promotes overgrowth of Bifidobacterium pseudolongum, and that oral administration of B. pseudolon2024-01-01T00:00:00Z2024 Dec2026-06-02T20:12:15.434Z2025-04-05T21:19:26.055ZS-EPMC117422653924409010.1016/j.mucimm.2024.08.010