LAUSR

Dietary intervention with short‐chain galacto‐oligosaccharides (scGOS), long‐chain fructo‐oligosaccharides (lcFOS) and Bifidobacterium breve M‐16V (Bb) (GF/Bb) suppresses food allergic symptoms in mice, potentially via intestinal epithelial cell (IEC)–derived galectin‐9. Furthermore, in vitro studies showed galacto‐ and fructo‐oligosaccharides (GF) to enhance the immunomodulatory capacity of a TLR9 ligand representing bacterial CpG DNA when exposed to IEC. In this study, we investigated whether GF/Bb modulates dendritic cells (DCs) and subsequent Th2 and regulatory T cell (Treg) frequency in the small intestinal lamina propria (SI‐LP). BALB/c mice were fed GF/Bb during oral OVA sensitization. DC and T cell phenotype were determined in SI‐LP mononuclear cells using flow cytometry. Murine bone marrow‐derived DCs (BMDCs) were exposed to recombinant galectin‐9 or human monocyte‐derived DCs (moDCs) and were cultured in IEC‐conditioned medium from GF and TLR9 ligand‐exposed HT‐29 cells. GF/Bb reduced allergic symptoms and enhanced serum galectin‐9 levels, while suppressing activation, restoring phagocytic capacity, and normalizing CD103 expression of SI‐LP DCs of OVA‐allergic mice. In vitro, galectin‐9 suppressed LPS‐induced activation markers and cytokine secretion by BMDCs, and IEC‐conditioned medium suppressed moDC activation in a galectin‐9–dependent manner. Besides suppression of SI‐LP DC activation, dietary GF/Bb also lowered the frequency of activated Th2 cells, while enhancing Treg in the SI‐LP of OVA‐allergic mice compared to the control diet. Dietary intervention with GF/Bb enhances galectin‐9 and suppresses allergic symptoms of OVA‐allergic mice in association with reduced intestinal DC and Th2 activation and increased Treg frequency in these mice.