Potential of probiotic strains to modulate the inflammatory responses of epithelial and immune cells in vitro

Lactobacilli are important human commensal microbiota that are considered to be probiotic as they have been shown to reduce pathogenic infections and chronic inflammation. This study compared 4 strains of lactobacilli for their probiotic potential. These 4 strains showed varying capacities for adhesion and cytokine induction (interleukin [IL]-8 and IL-10) in different human epithelial cells, such as primary cultures of buccal cavity cells, and established cell lines derived from epithelia of the pharynx, intestine and cervix. After exposure to lactobacilli, secretion of cytokines (IL- 10, IL-12p70, interferon-?, and tumor necrosis factor-?) was induced at varying levels in different cultures of human immune cells, including dendritic cells, monocyte-depleted peripheral blood mononuclear cells, CD14+ cells, CD4+CD25- T cells, and regulatory T-cells. Growth inhibition of pathogenic strains was detectable in the presence of lactobacilli in vitro. Moreover, among the 4 strains tested, Lactobacillus salivarius sp. salicinius AP-32 was found to have the highest probiotic potential. This study highlights the complex host-pathogen-microbiota interactions and indicates that a combination of strains may have to be used to provide all the desirable probiotic benefits.