In vitro activation of mononuclear cells by two probiotics:: Lactobacillus paracasei I 1688, Lactobacillus salivarius I 1794, and their mixture (PSMIX)

Background: Most studies on probiotics have described their effects on the human immune system after ingestion of LAB, but little is known about their effect on in vitro stimulation of human immune cells. Aim of the study: Evaluate the in vitro activity of Lactobacillus paracasei (11688), Lactobacillus salivarius (1 1794), and a commercial mix of the two (PSMIX, Proge Farm), on immune cells from healthy individuals. Materials: Two probiotic strains, Lactobacillus salivarius (1 1794; Proge Farm, Italy) and Lactobacillus paracasei (1 1688; Proge Farm, Italy), which are contained in the functional food ENTEROBACILLI, were evaluated for their ability to stimulate peripheral blood mononuclear cells and modulate surface phenotype and cytokine production. Results: All subjects responded to the bacteria, with different levels of response. The cell populations that showed a significant percent increase were CD4+/CD25+ cells (T-helper activated regulatory cells), CD8+/CD25+ (T-suppressor/cytotoxic activated cells), and CD16+/CD56+ (NK cells) (p<0.05). IL-12 and IFN-gamma in vitro production significantly increased with exposure to probiotics (p<0.05 for both). Conclusions: This study provides the first evidence that Lactobacillus paracasei and Lactobacillus salivarius are capable of inducing a specific immune response that may be useful in the clinical setting for improving innate and adaptive immune responses.