Synbiotic Effects of the Dietary Fiber Long-Chain Inulin and Probiotic Lactobacillus acidophilus W37 can be Caused by Direct, Synergistic Stimulation of Immune Toll-Like Receptors and Dendritic Cells

SCOPE: Synbiotic effects of dietary fibers and lactobacilli are usually explained by synergistic modulation of gut-microbiota. New insight however has demonstrated that both dietary fibers and lactobacilli can directly stimulate immune cells and benefit consumer-immunity. Here we investigated synergistic effects of immune-active long-chain inulin (lcITF) and L. acidophilus W37 (LaW37) on dendritic cells (DCs). METHODS AND RESULTS: Effects of lcITF and LaW37 alone or combined were studied on Toll-like receptor (TLRs) signaling and cytokine secretion by DCs in the presence and absence of media of intestinal epithelial cell (IEC) exposed to the ingredients. Also, we investigated the effects on DC-responses against Salmonella Typhimurium (STM). Synergistic effects were observed on TLR2 and 3. Synergistic effects were not always pro-inflammatory. LaW37 was strongly pro-inflammatory while cytokine-responses were regulatory when combined with lcITF. Exposure of DCs to IECs-medium changed the DCs response which revealed synergistic enhancing effects of lcITF/LaW37 on production of IL-6 and IL-8. DCs response in presence of STM and LaW37 were so strong that lcITF had no additional effect. CONCLUSION: We demonstrated that synbiotic effects of dietary fibers and bacteria are not limited to effects on gut microbiota but can also occur by synergistically directly stimulating IECs and/or immune cells. This article is protected by copyright. All rights reserved.