Orally administered Lactobacillus paracasei KW3110 induces in vivo IL-12 production.

Lactic acid bacteria (LAB) are popularly used as probiotics, and some strains of LAB have anti-allergic functions in vivo. Although in vitro studies show that LAB modulate the T helper type (Th) 1/Th2 balance and inhibit IgE secretion by inducing IL-12, it is not known how LAB regulates allergies in vivo. In this study, we evaluated in vivo IL-12 production after oral administration of Lactobacillus paracasei KW3110, a strain reported to improve allergies, to mice. Orally administered KW3110 interacted with CD11b positive cells and induced IL-12 mRNA expression at Peyer's patch. In addition, blood IL-12 levels increased transiently 10 h after administration of KW3110. Based on these results, we found that oral administration of KW3110 induces IL-12 in vivo. Our findings should contribute to understanding of the in vivo function of LAB.