Plasmacytoid dendritic cells mediate anti-inflammatory responses to a gut commensal molecule via both innate and adaptive mechanisms

Cell Host Microbe. 2014 Apr 9;15(4):413-23. doi: 10.1016/j.chom.2014.03.006.


Polysaccharide A (PSA), the archetypical immunomodulatory molecule of the gut commensal Bacteroides fragilis, induces regulatory T cells to secrete the anti-inflammatory cytokine interleukin-10 (IL-10). The cellular mediators of PSA's immunomodulatory properties are incompletely understood. In a mouse model of colitis, we find that PSA requires both innate and adaptive immune mechanisms to generate protection. Plasmacytoid DCs (PDCs) exposed to PSA do not produce proinflammatory cytokines, but instead they specifically stimulate IL-10 secretion by CD4+ T cells and efficiently mediate PSA-afforded immunoprotection. PSA induces and preferentially ligates Toll-like receptor 2 on PDCs but not on conventional DCs. Compared with other TLR2 ligands, PSA is better at enhancing PDC expression of costimulatory molecules required for protection against colitis. PDCs can thus orchestrate the beneficial immunoregulatory interaction of commensal microbial molecules, such as PSA, through both innate and adaptive immune mechanisms.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptive Immunity
  • Adoptive Transfer
  • Animals
  • B7-1 Antigen / genetics
  • B7-2 Antigen / genetics
  • Bacteroides fragilis / immunology*
  • Bone Marrow Cells / immunology
  • CD28 Antigens / genetics
  • CD4-Positive T-Lymphocytes / immunology
  • Cells, Cultured
  • Dendritic Cells / immunology*
  • Dendritic Cells / transplantation
  • Encephalomyelitis, Autoimmune, Experimental / immunology*
  • Female
  • Gastrointestinal Tract / immunology*
  • Gastrointestinal Tract / microbiology
  • Immunity, Innate
  • Inducible T-Cell Co-Stimulator Ligand / genetics
  • Inflammation / immunology
  • Interleukin-10 / metabolism
  • Lymphocyte Depletion
  • Mice
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Models, Animal
  • Polysaccharides, Bacterial / immunology*
  • Toll-Like Receptor 2 / biosynthesis
  • Toll-Like Receptor 2 / metabolism


  • B7-1 Antigen
  • B7-2 Antigen
  • CD28 Antigens
  • Cd86 protein, mouse
  • IL10 protein, mouse
  • Icosl protein, mouse
  • Inducible T-Cell Co-Stimulator Ligand
  • Polysaccharides, Bacterial
  • Tlr2 protein, mouse
  • Toll-Like Receptor 2
  • Interleukin-10