Lactobacilli and streptococci induce interleukin-12 (IL-12), IL-18, and gamma interferon production in human peripheral blood mononuclear cells

Human peripheral blood mononuclear cells (PBMC) were stimulated with three nonpathogenic Lactobacillus strains and with one pathogenic Streptococcus p yogenes strain, and cytokine gene expression and protein production were an alyzed. All bacteria strongly induced interleukin-1 beta (IL-1 beta), IL-6, and tumor necrosis factor alpha mRNA expression and protein production. S. pyogenes was the most potent inducer of secretion of IL-12 and gamma inter feron (IFN-gamma), and two of three Lactobacillus strains induced IL-12 and IFN-gamma production. All strains induced IL-18 protein production. IL-10 and IL-4 production was induced weakly and not at all, respectively. Our da ta show that nonpathogenic lactobacilli and pathogenic streptococci can ind uce Th1 type cytokines IL-12, IL-18, and IFN-gamma in human PBMC.