Immunostimulatory Activities of Lactic Acid Bacteria via Toll-like Receptors

Many works on the biological functions of dairy lactic acid bacteria (LAB) have contributed to the application of LAB in functional foods and supplements in the global market. More recently, the new term "immunobiotics", has been proposed to identify probiotic bacteria that promote health through activation of intestinal immunity from those with strictly local immunity, and expected for an appropriate evolutionary development. We have studied specific effector molecules and their receptor targets. Recently, we found that immunostimulatory AT oligonucleotide (AT-ODN), but not CpG ODN, from Lactobacillus gasseri JCM 1131 triggered. immune responses via Toll-like receptor 9 (TLR 9), which has been identified as a particular receptor for bacterial DNA containing the specific sequence pattern of unmethylated CpG dinucleotide. Through the discovery of TLR 9, possible molecular mechanisms in immune responses through bacterial DNA have been rapidly revealed in mice. Recently, we found that ATODN from Lactobacillus gasseri, possibly induces immunoactivation in Peyer's patches (Pps) via TLR 9. We demonstrated that TLR 9 is a receptor for not only CpG but also for non-CpG AT ODN as a result of the induction of nuclear factor-k B (NF-k B) activation by gene reporter assay. This review describes our recent study on the immunostimulatory activity of LAB via TLRs, especially TLR 9 and 2 and discuss future trends in the development of "Immunobiotic Foods" through intestinal immunoregulation mediated by "Immunobiotic" LAB