Heat-killed Lactobacillus paracasei K71 isolated from Sakekasu (sake lees) enhances Th1 response, NK cell cytotoxicity and fecal IgA content in normal BALB/c mice

Abstract

Lactobacillus paracasei K71 (K71) isolated from Japanese sake lees (Sakekasu) was previously shown to enhance IL-12 production in mouse spleen cell culture. In this study, we examined whether heat-killed K71 exerts immunostimulatory effects in normal BALB/c mice. Six-week dietary supplementation with 0.2% heat-killed K71 resulted in significantly higher levels of serum IgG2a and fecal IgA than control mice. Upon administration, heat-killed K71 increased IFN-γ production in Peyer's patch cells while simultaneously suppressing IL-4 production in spleen cells. Spleen cells from mice fed heat-killed K71 exhibited a significant increase in cytotoxicity against YAC-1 cells. Furthermore, splenic CD49b⁺NKp46⁺ NK cells from mice fed heat-killed K71 showed significantly enhanced IFN-γ production. These results suggest that oral intake of K71 may augment Th1 type immune function and innate immunity, thereby potentially preventing infections and/or tumorigenesis.