Probiotic modulation of dendritic cells co-cultured with intestinal epithelial cells

AIM: To investigate cytokine production and cell surface phenotypes of dendritic cells (DC) in the presence of epithelial cells stimulated by probiotics.METHODS: Mouse DC were cultured alone or together with mouse epithelial cell monolayers in normal or inverted systems and were stimulated with heat-killed probiotic bacteria, Bifidobacterium lactis AD011 (BL), Bifidobacterium bifidum BGN4 (BB), Lactobacillus casei IBS041 (LC), and Lactobacillus acidophilus AD031 (LA), for 12 h. Cytokine levels in the culture supernatants were determined by enzyme-linked immunosorbent assay and phenotypic analysis of DC was investigated by flow cytometry.RESULTS: BB and LC in single-cultured DC increased the expression of I-Ad, CD86 and CD40 (I-Ad, 18.51 vs 30.88, 46.11; CD86, 62.74 vs 92.7, 104.12; CD40, 0.67 vs 6.39, 3.37, P < 0.05). All of the experimental probiotics increased the production of inflammatory cytokines, interleukin (IL)-6 and tumor necrosis factor (TNF)-α. However, in the normal co-culture systems, LC and LA decreased the expression of I-A^d (39.46 vs 30.32, 33.26, P < 0.05), and none of the experimental probiotics increased the levels of IL-6 or TNF-α. In the inverted co-culture systems, LC decreased the expression of CD40 (1.36 vs -2.27, P < 0.05), and all of the experimental probiotics decreased the levels of IL-6. In addition, BL increased the production of IL-10 (103.8 vs 166.0, P < 0.05) and LC and LA increased transforming growth factor-β secretion (235.9 vs 618.9, 607.6, P < 0.05).CONCLUSION: These results suggest that specific probiotic strains exert differential immune modulation mediated by the interaction of dendritic cells and epithelial cells in the homeostasis of gastrointestinal tract.