Comparison of the Immunomodulatory Effects of Live and Heat-killed Lactobacillus pentosus S-PT84

Lactobacillus pentosus S-PT84, which was isolated from Kyoto pickles, enhances splenic natural killer (NK) cell activity, increases IgA production from Peyer’s patch cells and has high T-helper 1 (Th1) cytokine and type 1interferon-inducing activity. However, all of these effects were obtained by using heat-killed S-PT84. In the present study, we investigated the immunomodulatory effect of live and heat-killed S-PT84 in BALB/c mice. Unexpectedly, live S-PT84 indicated weak activity on Th1 cytokine (interleukin-12 or interferon-γ) production from splenocytes compared to heat-killed S-PT84 in vitro. Similar tendencies were also shown in S-PT84 having different cell wall thickness. Next, we compared the immunomodulatory effect after oral ingestion of each S-PT84. The results indicated splenic NK activity was equally enhanced by live or heat-killed S-PT84 ingestion, though heat-killed S-PT84 indicated slightly higher activity in interferon-γ production and inclination toward Th1 immunity. These results suggested that both live and heat-killed S-PT84 have an equal immunomodulatory effect in BALB/c mice. It is thought that the use of heat-killed S-PT84 is advantageous from the viewpoint of ease of handling compared to live S-PT84.