Probiotic Bacteria Induce Regulatory Cytokine Production via Dendritic Cells

Hvas, C. L.; Kelsen, J.; Agnholt, J.; Höllsberg, P.; Dahlerup, J. F.

Probiotic bacteria, e.g. Lactobacillus spp., may improve diseases such as chronic inflammatory bowel disease. We examined cytokine production and phenotypic change after in vitro stimulation of T cells from healthy volunteers using different probiotic strains. Methods: T cells were cultured from colonic biopsies from eight healthy volunteers (Agnholt and Kaltoft, Exp Clin Immunogenet 2001;18:213–25), and dendritic cells were matured from their peripheral blood mononuclear cells. T‐cell cultures were stimulated with autologous bacterial sonicate or strains of Lactobacillus spp., with and without the addition of dendritic cells. Cytokine levels (TNF‐α, IFN‐γ, IL‐10 and GM‐CSF) and phenotype (CD3, CD4, CD25 and CD69) were measured on day 4. Results: Lactobacillus spp. induced higher productions of TNF‐α and IL‐10 than did autologous bacteria. In presence of dendritic cells, the production of all cytokines increased. However, the increases of IFN‐γ and TNF‐α were more pronounced in wells with autologous bacteria than in wells with Lactobacillus spp. The addition of dendritic cells upregulated CD25 expression without simultaneous upregulation of CD69. The upregulation was pronounced after stimulation with Lactobacillus rhamnosus GG compared with autologous bacteria and other lactobacilli. Discussion: In presence of dendritic cells, autologous bacteria induced inflammatory cytokines, while probiotics mainly induced regulatory cytokines. Lactobacillus rhamnosus GG induced a regulatory phenotype (cd25(+)), in part mediated by dendritic cells. Future studies will address whether this shift to a CD25(+) phenotype represents a differentiation into competent regulatory T cells. In a clinical context, such cells might be used for treatment of inflammatory diseases.