Background: Many types of fermented food are consumed in Japan. Although some are produced by plant-origin lactic-acid bacteria (LAB) fermentation, the physiological functions of such bacteria remain unclear. We therefore isolated LAB of plant origin from Kyoto pickles and determined the immunological activity of heat-killed preparations of plant-origin LAB. Methods: The Lactobacillus pentosus strain S-PT84 was selected from among 16 LAB of plant origin as the strongest interleukin (IL)-12-inducing strain. IL-12- and IL-10-inducing activities were determined with macrophages from BALB/c mice. The in vivo immunomodulating effect of S-PT84was determined with BALB/c mice fed S-PT84. The antiallergic activity of S-PT84 was examined in ovalbumin (OVA)/alum-administered BALB/c mice. Results: The L. pentosus strain S-PT84 induced production of both IL-12 and IL-10 in vitro. S-PT84 enhanced splenic natural-killer activity and modulated the T helper (Th) type 1/type 2 balance toward a Th1-dominant state. In the OVA-induced allergy model, orally administered S-PT84 lowered serum IgE levels and suppressed active cutaneous anaphylaxis reaction and splenic IL-4 production. IL-10 production from splenocytes of OVA-immunized mice was upregulated by feeding S-PT84. Conclusions: Despite heat-killing, S-PT84 exhibited antiallergic effects by modulating the Th1/Th2 balance and inducing regulatory T cells. The L. pentosus strain S-PT84, which is of plant origin and isolated from a traditional Japanese food, is expected to be useful for treatment of many immune diseases including allergies, tumors, infectious diseases and auto-immune diseases.

Lactobacillus pentosus (L. pentosus) strain S-PT84, isolated from Kyoto pickles, enhances splenic natural killer (NK) cell activity, and has high T-helper1 (Th1) cytokine and type 1-IFN (IFN-α) inducing activity. In the present study, we investigated the influence of S-PT84 ingestion on the mucosal immunity of healthy and Salmonella Typhimurium (S. Typhimurium)-infected mice. In the S. Typhimurium infection model, numbers of S. Typhimurium in feces and the spleen were significantly decreased, and body weight loss and deterioration in the general health score of S. Typhimurium-infected mice were improved by S-PT84 ingestion. Oral administration of S-PT84 enhanced IL-5 and IL-6 production from Peyer’s patch cells in vitro, with a concomitant significant increase in IgA production from Peyer’s patch cells, which may explain the mechanism of enhanced IgA production in the small intestine in vivo. These results suggest that S-PT84 ingestion is useful for the maintenance of health or the improvement of certain symptoms during pathogen infection.