Specific Lactobacillus species differentially activate Toll-like receptors and downstream signals in dendritic cells

Abstract

Background: Dendritic cells (DCs) regulate mucosal T-cell immunity and encounter several distinct bacteria of the gut flora, including lactobacilli. Gram-positive lactobacilli have been suggested to play an important role in exerting adjuvanticity effects on innate immune cells at mucosal sites. Aims & methods: In the present report, we studied the effects of specific Lactobacillus species on human monocyte derived DCs. Results: We show that lactobacilli activate DCs by differentially inducing the expression of Toll-like receptors and bioactive IL-12 in Lactobacillus-treated DCs. Further, these specific Lactobacillus spp. did not activate the phosphorylation of p38 MAPK, which might be a downstream effect of the remarkable capacity of lactobacilli to induce IL-12 in DCs that skew T cells significantly toward an IFN-γ-secreting Th1 response. Conclusion: These results highlight an important role of specific Lactobacillus spp. as adjuvants in triggering DC function, which in turn may determine the immunological outcome in an environment wherein innate cells reside.

Keywords::

• adjuvant
• dendritic cell
• Lactobacillus
• MAP kinase
• Toll-like receptor

Acknowledgements

The authors thank C Morris, X Alvarez and G Ruthel for fruitful discussion.

Financial & competing interests disclosure

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

No writing assistance was utilized in the production of this manuscript.

Ethical conduct of research

The authors state they have obtained appropriate institutional review board approval or have followed the prinicples outlined in the Declaration of Helsinski for all human or animal experimental investigations. In addition, for investigations involoving human subjects, informed consent has been obtained from the participants involved.