Human dendritic cell DC-SIGN and TLR-2 mediate complementary immune regulatory activities in response to Lactobacillus rhamnosus JB-1

PLoS One. 2015 Mar 27;10(3):e0120261. doi: 10.1371/journal.pone.0120261. eCollection 2015.

Abstract

The microbiota is required for optimal host development and ongoing immune homeostasis. Lactobacilli are common inhabitants of the mammalian large intestine and immunoregulatory effects have been described for certain, but not all, strains. The mechanisms underpinning these protective effects are beginning to be elucidated. One such protective organism is Lactobacillus rhamnosus JB-1 (Lb. rhamnosus JB-1). Lb. murinus has no such anti-inflammatory protective effects and was used as a comparator organism. Human monocyte-derived dendritic cells (MDDCs) were co-incubated with bacteria and analysed over time for bacterial adhesion and intracellular processing, costimulatory molecule expression, cytokine secretion and induction of lymphocyte polarization. Neutralising antibodies were utilized to identify the responsible MDDC receptors. Lb. rhamnosus JB-1 adhered to MDDCs, but internalization and intracellular processing was significantly delayed, compared to Lb. murinus which was rapidly internalized and processed. Lb. murinus induced CD80 and CD86 expression, accompanied by high levels of cytokine secretion, while Lb. rhamnosus JB-1 was a poor inducer of costimulatory molecule expression and cytokine secretion. Lb. rhamnosus JB-1 primed MDDCs induced Foxp3 expression in autologous lymphocytes, while Lb. murinus primed MDDCs induced Foxp3, T-bet and Ror-γt expression. DC-SIGN was required for Lb. rhamnosus JB-1 adhesion and influenced IL-12 secretion, while TLR-2 influenced IL-10 and IL-12 secretion. Here we demonstrate that the delayed kinetics of bacterial processing by MDDCs correlates with MDDC activation and stimulation of lymphocytes. Thus, inhibition or delay of intracellular processing may be a novel strategy by which certain commensals may avoid the induction of proinflammatory responses.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Adhesion Molecules / immunology*
  • Cells, Cultured
  • Cytokines / metabolism
  • Dendritic Cells / cytology
  • Dendritic Cells / immunology*
  • Humans
  • Immunologic Factors / pharmacology
  • Lacticaseibacillus rhamnosus / immunology*
  • Lectins, C-Type / immunology*
  • Lymphocyte Activation / immunology
  • Monocytes / cytology
  • Monocytes / immunology*
  • Receptors, Cell Surface / immunology*
  • Toll-Like Receptor 2 / immunology*

Substances

  • Cell Adhesion Molecules
  • Cytokines
  • DC-specific ICAM-3 grabbing nonintegrin
  • Immunologic Factors
  • Lectins, C-Type
  • Receptors, Cell Surface
  • TLR2 protein, human
  • Toll-Like Receptor 2

Grants and funding

The authors are supported by Swiss National Foundation grants (project numbers 310030-127356 and 310030_144219), Allergiestiftung Ulrich Müller-Gierok, European Union research grants and EU Marie Curie grants. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.