Suppressive effects of bifidobacterium breve strain M-16V on T-helper type 2 immune responses in a murine model.

The Bifidobacterium breve M-16V strain has previously been shown to be effective in infants in improving the symptoms of allergic hypersensitivity to cow's milk and atopic dermatitis. In the current study, we investigated the effect of an oral administration of M-16V on immunoglobulin (Ig) E production in BALB/c mice. Live M-16V was orally administered to ovalbumin (OVA)-immunized mice for 3 weeks at a dose level of 5x10(8) colony-forming unit (cfu)/0.5 ml/d/animal. While M-16V treatment significantly reduced the serum levels of total IgE, OVA-specific IgE and OVA-specific IgG1, as compared to controls, it did not affect the serum level of OVA-specific IgG2a. In M-16V-administered mice, there was a significant decrease in the serum OVA-specific IgG1/IgG2a ratio. In addition, while ex vivo production of interleukin (IL)-4 by the splenocytes from M-16V-administered mice was significantly lower as compared to controls, there was no difference in the production of gamma-interferon (IFN-gamma) and IL-10. We also examined the effect of M-16V on cytokine and IgE production from OVA-sensitized splenocytes via restimulation with OVA in vitro. While M-16V suppressed OVA-induced total IgE and IL-4 production and induced secretion of IFN-gamma and IL-10 in a dose-dependent manner, it was not able to induce IL-12. We concluded that oral administration of M-16V suppressed the T-helper type (Th) 2 immune response and IgE production and modulated the systemic Th1/Th2 balance, and which was at least partially independent of the Th1 cytokine induction. These results suggest that M-16V may potentially have an antiallergic activity.