Antitumor activity and action mechanisms of Lactobacillus casei through the regulation of immune responses

Lactobacillus casei strain Shirota (LcS) has been demonstrated to have beneficial effects in numerous disease models, especially murine autoimmune disease and carcinogenesis models, via host immune modulation. It has also been reported that LcS induced recovery of the host immune responses that were decreased by treatment with carcinogens, and that augmented the natural killer activity and T cell functions of host immune cells. After LcS is ingested by the host, it is incorporated into M cells in Peyer's patches (PP) and digested to form active components. In PP, macrophages or dendritic cells that phagocytosed LcS gained ability to produce tumor necrosis factor-alpha. The components of LcS digested in PP were then recognized through toll-like receptor 2 in macrophages, resulting in the production of several cytokines which elicit varied responses in host immune cells. Also, it was observed by 2D-PAGE analyses that the expression level and/or the phosphorylation of some proteins in PP and mesenteric lymph nodes were definitely altered after the ingestion of LcS, providing more evidence of cellular responses.