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Recently, we found a novel function of the lactic acid bacterium Tetragenococcus halophilus derived from miso, a fermented soy paste, that induces interleukin (IL)-22 production in B cells preferentially. IL-22 plays a critical role in barrier functions in the gut and skin. We further screened other bacteria species, namely, Enterococcus, Lactobacillus, Lactococcus, Leuconostoc, Weissella, Pediococcus, and Bacillus, in addition to Tetragenococcus and found that some of them possessed robust IL-22-inducible function in B cells in vitro. This process resulted in the augmented expression of activation markers CD86 and CD69 on B and T cells, respectively. However, these observations were not correlated with IL-22 production. We isolated Bacillus coagulans sc-09 from miso and determined it to be the best strain to induce robust IL-22 production in B cells. Furthermore, feeding B. coagulans sc-09 to mice augmented the barrier function of the skin regardless of gut microbiota.

ObjectiveAlthough immunoglobulin A (IgA) is abundantly expressed in the gut and known to be an important component of mucosal barriers against luminal pathogens, its precise function remains unclear. Therefore, we tried to elucidate the effect of IgA on gut homeostasis maintenance and its mechanism.DesignWe generated various IgA mutant mouse lines using the CRISPR/Cas9 genome editing system. Then, we evaluated the effect on the small intestinal homeostasis, pathology, intestinal microbiota, cytokine production, and immune cell activation using intravital imaging.ResultsWe obtained two lines, with one that contained a tm/tm) and the other that lacked the most constant region of the IgH α chain, which resulted in the deficiency of IgA production (IgA−/−). IgA−/− exhibited spontaneous inflammation in the ileum but not the other parts of the gastrointestinal tract. Associated with this, there were significantly increased lamina propria CD4+ T cells, elevated productions of IFN-γ and IL-17, increased ileal segmented filamentous bacteria and skewed intestinal microflora composition. Intravital imaging using Ca2+ biosensor showed that IgA−/− had elevated Ca2+ signalling in Peyer’s patch B cells. On the other hand, IgAtm/tm seemed to be normal, suggesting that the IgA cytoplasmic tail is dispensable for the prevention of the intestinal disorder.ConclusionIgA plays an important role in the mucosal homeostasis associated with the regulation of intestinal microbiota and protection against mucosal inflammation especially in the ileum.

Propolis possesses several immunological functions. We recently generated a conditional Ca2+ biosensor yellow cameleon (YC3.60) transgenic mouse line and established a five-dimensional (5D) (x, y, z, time, and Ca2+ signaling) system for intravital imaging of lymphoid tissues, including Peyer's patches (PPs). To assess the effects of propolis on immune cells, we analyzed Ca2+ signaling in vitro and in vivo using CD11c-Cre/YC3.60flox transgenic mice, in which CD11c+ dendritic cells (DCs) specifically express YC3.60. We found that propolis induced Ca2+ signaling in DCs in the PPs. Intravital imaging of PPs also showed that an intraperitoneal injection of propolis augmented Ca2+ signaling in CD11c+ cells, suggesting that propolis possesses immune-stimulating activity. Furthermore, CD11c+ cells in PPs in mice administrated propolis indicated an increase in Ca2+ signaling. Our results indicate that propolis induces immunogenicity under physiological conditions.

Tetragenococcus halophilus is a halophilic lactic acid bacterium that exists in the traditional Japanese seasoning miso—a fermented soy paste. Considering the popularity of miso as a component of healthy diet, we attempted to evaluate the immunoregulatory functions of T. halophilus spices isolated from miso. We screened 56 strains that facilitated the upregulation of activation markers such as CD86 and CD69 on B cells and T cells in vitro. Of these, 7 strains (Nos. 1, 3, 13, 15, 19, 30, and 31) were found to preferentially induce the CD86 expression on B cells. Furthermore, DNA microarray analysis revealed that T. halophilus strain No. 1 significantly augmented the gene expressions of CD86, CD70, IL-10, INF-γ, and IL-22 in B cells. We confirmed these results at the protein level by flow cytometry. Mice feeding diet containing 1% T. halophilus No. 1 exhibited significantly greater IgA production in the serum. Furthermore, a diet containing 1% T. halophilus No. 1 augmented ovoalbumin (OVA)-specific IgG titer in mice upon OVA/alum immunization. Thus, we demonstrated that T. halophilus No. 1 is a strong immunomodulatory strain with potential as a probiotic.