Fructooligosaccharides supplementation associates with tolerogenic DC-Treg responses in a preventive model of DSS-induced colitis

Fructooligosaccharides (FOS) have been shown to alleviate DSS-induced acute colitis, but the underlying immune mechanisms remain unclear. Here, we investigated whether the protective effect of FOS is associated with the modulation of intestinal dendritic cell (DC) and regulatory T cell (Treg) responses in a preventive mouse model. In vivo , FOS supplementation (2 g/kg for two weeks) reduced disease activity and colonic inflammation, increased CD103 + DCs while decreasing CD103 − CD11b + DCs in mesenteric lymph nodes, and enhanced Treg and IL-10 + cell responses with spatial proximity in the inflamed colonic mucosa. In vitro , FOS-conditioned fecal fermentation selectively enriched Lactobacillus and suppressed LPS-induced BMDC activation, as shown by a reduced proportion of CD86ʰⁱ cells. Collectively, these findings suggest that FOS might promote a tolerogenic DC phenotype that supports anti-inflammatory Treg responses, indicating its potential as a prebiotic intervention for IBD.