MyD88 signaling in dendritic cells and the intestinal epithelium controls immunity against intestinal infection with C. rodentium

PLoS Pathog. 2017 May 16;13(5):e1006357. doi: 10.1371/journal.ppat.1006357. eCollection 2017 May.

Abstract

MyD88-mediated signaling downstream of Toll-like receptors and the IL-1 receptor family is critically involved in the induction of protective host responses upon infections. Although it is known that MyD88-deficient mice are highly susceptible to a wide range of bacterial infections, the cell type-specific contribution of MyD88 in protecting the host against intestinal bacterial infection is only poorly understood. In order to investigate the importance of MyD88 in specific immune and nonimmune cell types during intestinal infection, we employed a novel murine knock-in model for MyD88 that enables the cell type-specific reactivation of functional MyD88 expression in otherwise MyD88-deficient mice. We report here that functional MyD88 signaling in CD11c+ cells was sufficient to activate intestinal dendritic cells (DC) and to induce the early group 3 innate lymphoid cell (ILC3) response as well as the development of colonic Th17/Th1 cells in response to infection with the intestinal pathogen C. rodentium. In contrast, restricting MyD88 signaling to several other cell types, including macrophages (MO), T cells or ILC3 did not induce efficient intestinal immune responses upon infection. However, we observed that the functional expression of MyD88 in intestinal epithelial cells (IEC) also partially protected the mice during intestinal infection, which was associated with enhanced epithelial barrier integrity and increased expression of the antimicrobial peptide RegIIIγ and the acute phase protein SAA1 by epithelial cells. Together, our data suggest that MyD88 signaling in DC and IEC is both essential and sufficient to induce a full spectrum of host responses upon intestinal infection with C. rodentium.

MeSH terms

  • Animals
  • Citrobacter rodentium / immunology*
  • Colon / immunology
  • Colon / microbiology
  • Dendritic Cells / immunology
  • Dendritic Cells / microbiology
  • Enterobacteriaceae Infections / immunology*
  • Enterobacteriaceae Infections / microbiology
  • Enterobacteriaceae Infections / pathology
  • Epithelial Cells / immunology
  • Epithelial Cells / microbiology
  • Gene Knock-In Techniques
  • Intestinal Mucosa / immunology
  • Intestinal Mucosa / microbiology
  • Macrophages / immunology
  • Macrophages / microbiology
  • Mice
  • Mice, Inbred C57BL
  • Myeloid Differentiation Factor 88 / genetics
  • Myeloid Differentiation Factor 88 / metabolism*
  • Receptors, Interleukin-1 / metabolism
  • Signal Transduction*
  • Th1 Cells / immunology
  • Th1 Cells / microbiology
  • Th17 Cells / immunology
  • Th17 Cells / microbiology
  • Toll-Like Receptors / genetics
  • Toll-Like Receptors / metabolism

Substances

  • Myd88 protein, mouse
  • Myeloid Differentiation Factor 88
  • Receptors, Interleukin-1
  • Toll-Like Receptors

Grants and funding

This work was supported by the Deutsche Forschungsgemeinschaft (DFG) with grants LO1415/2-1 to ML and TSp and LO1415/7-1 to ML. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.