IgA secretion at mucosal sites is important for host defence against pathogens as well as maintaining the symbiosis with microorganisms present in the small intestine that affect IgA production. In the present study, we tested the ability of 5 strains of lactic acid bacteria stimulating IgA production, being Pediococcus acidilactici K15 selected as the most effective on inducing this protective immunoglobulin. We found that this response was mainly induced via IL-10, as efficiently as IL-6, secreted by K15-stimulated dendritic cells. Furthermore, bacterial RNA was largely responsible for the induction of these cytokines; double-stranded RNA was a major causative molecule for IL-6 production whereas single-stranded RNA was critical factor for IL-10 production. In a randomized, double-blind, placebo-controlled clinical trial, ingestion of K15 significantly increased the secretory IgA (sIgA) concentration in saliva compared with the basal level observed before this intervention. These results indicate that functional lactic acid bacteria induce IL-6 and IL-10 production by dendritic cells, which contribute to upregulating the sIgA concentration at mucosal sites in humans.
The purpose of this study was to investigate the effect of cranberry polyphenol fraction on mutans streptococci. Hydrophobicity is an important factor in the adherence of bacteria to the tooth surface. We found that cranberry polyphenol fraction significantly decreased the hydrophobicity of Streptococcus sobrinus 6715, Streptococcus mutans MT8148R and JC2 in a dose-dependent manner (pϽ0.05). Biofilm formation by S. sobrinus 6715 and S. mutans MT8148R was inhibited by 100g/ml cranberry polyphenol fraction (pϽ0.01). When dosage was increased to 500g/ml, biofilm formation by S. mutans JC2 was significantly inhibited (pϽ0.05). Addition of 500g/ml cranberry polyphenol fraction to medium inhibited growth of S. mutans MT8148R compared with the control (pϽ0.05).
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