Lactobacillus isolates from healthy volunteers exert immunomodulatory effects on activated peripheral blood mononuclear cells.

As probiotics in the gut, Lactobacilli are believed to play important roles in the development and maintenance of both the mucosal and systemic immune system of the host. This study was aimed to investigate the immuno-modulatory function of candiate lactobacilli on T cells. Lactobacilli were isolated from healthy human feces and the microbiological characteristics were identified by API 50 CHL and randomly amplified polymorphic DNA (RAPD) assays. Anti-CD3 antibody activated peripheral blood mononuclear cells (PBMCs) were treated by viable, heat-killed lactobacilli and genomic DNA of lactobacilli, and cytokine profiles were tested by ELISA. Isolated lactobacilli C44 and C48 were identified as L. acidophilus and L. paracacei, which have properties of acid and bile tolerance and inhibitor effects on pathogens. Viable and heat-killed C44 and C48 induced low levels of proinflammatory cytokines (TNF-α, IL-6 and IL-8) and high levels of IFN-γ and IL-12p70 in PBMCs. In anti-CD3 antibody activated PBMCs, viable and heat-killed C44 increased Th2 cytokine levels (IL-5, IL-6 and IL-10), and simultaneously enhanced Th1 responses by inducing IFN-γ and IL-12p70 production. Different from that of lactabacillus strains, their genomic DNA induced low levels of IL-12p70, IFN-γ and proinflammatory cytokines in PBMCs with or without anti-CD3 antibody activation. These results provided in vitro evidence that the genomic DNA of strains of C44 and C48, especially C44, induced weaker inflammation, and may be potentially applied for treating allergic diseases.