Immunomodulatory effect of Lactococcus lactis JCM5805 on human plasmacytoid dendritic cells

Plasmacytoid dendritic cells (pDCs) play a crucial role in anti-viral immunity through production of large amounts of interferons (IFNs). A previous study revealed the existence of lactic acid bacteria that directly stimulate pDCs in mice. In this study, we demonstrated that Lactococcus lactis JCM5805 activates human pDCs and induces IFN production in vitro. In addition, our randomized, placebo-controlled, double blind test showed that yogurt fermented with L. lactis JCM5805 activated pDC activity in vivo. This effect was greater in low pDC subjects, and their ability to produce IFNs was increased from the beginning. Furthermore, the risk of morbidity from the common cold was suppressed in the L. lactis JCM5805 group compared with the placebo group. In conclusion, intake of L. lactis JCM5805 can directly activate pDCs and increase the ability to produce IFNs in vivo. Therefore, L. lactis JCM5805 may be a beneficial tool to enhance anti-viral immunity in humans.