A probiotic lactobacillus was discovered from lactobacilli of the Lactobacillus genus independently isolated from human adult feces. The probiotic lactobacillus was selected from other bacterial strains for: (1) being highly resistant to gastric acid/bile acid； (2) having a high promoting activity on IL-12 production from mouse derived spleen cells and a high Th1/Th2 balance-improving effect； (3) having a high ability to inhibit the production of antigen-specific IgE induced by intraperitoneally administering ovalbumin to BALB/c mice； (4) having a high ability to inhibit the production of antigen-specific IgE induced by orally administering a food antigen to C57BL/6N mice； (5) having a high Natural Killer cell-activating ability； (6) having a high IL-12 production-promoting activity on spleen cells and mesenteric lymph node cells derived from mice immunized with ovalbumin and a high Th1/Th2 balance-improving effect； and (7) having a high ability to suppress eosinophilia induced by a cedar pollen-extracted antigen. This discovery led to the completion of the present invention.
