A potential role for galectins in immune modulation upon exposure of human intestinal epithelial cells to non-digestible carbohydrates and TLR ligands

Objectives and Study: Early introduction of prebiotic nondigestible galacto- and fructo-oligosaccharides (scGOS/ lcFOS) was found to reduce the incidence of atopic eczema in infants at risk. In addition, probiotic bacteria and in particular bacterial CpG DNA may support tolerance induction. Combined use of pre- and probiotics was most effective in the prevention of cow's milk allergy in mice. In a novel in vitro coculture model the contribution of epithelial cells and epithelial derived galectins to the immune modulating effects of scGOS/lcFOS was investigated. Methods: Human intestinal epithelial cells (IEC; HT-29) were cultured on transwell filters and exposed to 0.5% scGOS/lcFOS together with Toll-like receptor (TLR) 4 (LPS) or TLR9 ligand (CpG DNA) and co-cultured with anti-CD3/28 activated healthy donor peripheral blood mononuclear cells (PBMC) in the basolateral compartment. PBMC derived cytokines were measured by ELISA and T-cell phenotype was analyzed by flow cytometry. In addition, expression of galectins by IEC was studied by real time PCR and fluorescence microscopy. Apical and basolateral galectin function was blocked using lactose (100 mM). Sucrose treatment (100mM) was used as control. Results: TLR9 ligation of IEC resulted in enhanced TH1 type IFN-gamma secretion by activated PBMC in association with increased galectin-3 and -9 expression by IEC (P