Effect of oral administration of Lactobacillus paracasei L9 on mouse systemic immunity and the immune response in the intestine

Yuanbo Zhu, Jun Zhu, Liang Zhao, Ming Zhang, Huiyuan Guo, Fazheng Ren


probiotic strain Lactobacillus paracasei L9, which was isolated from human intestine, was investigated for its immunomodulatory activity in vivo. Results showed that L9 improved systemic immunity by enhancing the phagocytic activity of peritoneal macrophages, the proliferation ratio of splenocytes, the IgG level in the serum and the level of IgA in the mucosa. Further, L9 induced the Th1-polarized immune response by elevating the IFN-γ/IL-4 ratio in the mucosa. This effect was confirmed by the enhanced IL-12-inducing activity of macrophages after in vitro stimulation of L9. Also detected was increased expression of TLR-2 mRNA in the mucosa. We predict that L9 could enhance innate immunity by activating TLR-2 in the mucosa, and enhance acquired immunity by promoting Th1 polarization through induced production of IL-12 by macrophages.

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