Lipoteichoic acids on Lactobacillus plantarum cell surfaces correlate with induction of interleukin-12p40 production

ABSTRACT Heat‐killed cells of Lactobacillus plantarum L‐137 are potent inducers of IL‐12 in vitro as well as in vivo and have been shown to have antiallergic, antitumor, and antiviral effects through this induction, which leads to a Th1 type immune response. To determine why L‐137 cells induce much greater IL‐12 production than the type strain Lactobacillus plantarum JCM1149, we examined the differences in their CW components. The L‐137 CW was found to have a higher alanine content and IL‐12p40 induction was significantly greater in comparison with JCM1149 CW, whereas peptidoglycans isolated from both strains did not cause IL‐12p40 induction. Because in purified CW preparations from gram‐positive bacteria, the presence of LTA, the major proinflammatory structure on these bacteria, has been known to have high alanine content, we investigated the responsiveness of both strains to anti‐LTA antibody by flow cytometry. L‐137 cells reacted more with anti‐LTA antibody than did JCM1149 cells. Furthermore, derivative strains of L‐137, cured of a specific plasmid pLTK11 of the 15 endogenous plasmids in wild‐type L‐137, had poor responsiveness to anti‐LTA antibody and showed lower IL‐12p40 inducing activity than the wild‐type L‐137 with pLTK11. Our results suggest that LTA expression on the cell surface causes IL‐12p40 induction, and that the above internal plasmid of L‐137 influences LTA synthesis and expression on the cell surface.