Abstract. Interleukin (IL)-17 acts as a potent inflammatory cytokine, and IL-17-producing cells (Th17 cells) have received much attention. However, the involvement of commensal and/or probiotic bacteria in IL-17 production has not been evaluated. In this study, we examined the suppressive effects of five bacteria species on IL-17 production in vitro and ex vivo. Among the five species studied, Bifidobacterium infantis inhibited IL-17 production but enhanced IL-27 production most potently in TGF-ß plus IL-6-stimulated murine splenocytes. B. infantis also inhibited IL-17 and eotaxin production from a dextran sodium sulfate-treated colon organ culture. The induction of IL-10 by B. infantis was observed both in the splenocytes and in the colon culture and was assumed, to a certain extent, to be important for suppressing IL-17 production. These findings suggest a novel immunomodulatory function of commensal bifidobacteria and further imply that these bacteria may be useful in the treatment of Th17-mediated diseases.

We evaluated the effects of a 50% methanol extract of Citrus unshiu powder (MEC) on cytokines in peripheral blood mononuclear cells (PBMCs) obtained from patients with seasonal allergic rhinitis to cedar pollen. The levels of cytokines, such as TNF-alpha, IFN-gamma, IL-2, IL-4, IL-5, IL-10, IL-12 (p70), IL-13, and GM-CSF, produced by pollen-stimulated PBMC were measured. We found that MEC suppressed pollen-induced TNF-alpha release and increased IFN-gamma release from PBMCs. The results suggest that Citrus unshiu powder has an immunomodulatory effect in vitro and that its use could improve seasonal allergic rhinitis symptoms.