Impaired Toll-like receptor 2 signalling in monocytes from 5-year-old allergic children

Clin Exp Immunol. 2009 Mar;155(3):387-94. doi: 10.1111/j.1365-2249.2008.03792.x.

Abstract

The relative composition of the two major monocytic subsets CD14(+)CD16(-) and CD14(+)CD16(+) is altered in some allergic diseases. These two subsets display different patterns of Toll-like receptor levels, which could have implications for activation of innate immunity leading to reduced immunoglobulin E-specific adaptive immune responses. This study aimed to investigate if allergic status at the age of 5 years is linked to differences in monocytic subset composition and their Toll-like receptor levels, and further, to determine if Toll-like receptor regulation and cytokine production upon microbial stimuli is influenced by the allergic phenotype. Peripheral blood mononuclear cells from 5-year-old allergic and non-allergic children were stimulated in vitro with lipopolysaccharide and peptidoglycan. Cells were analysed with flow cytometry for expression of CD14, Toll-like receptors 2 and 4 and p38-mitogen-activated protein kinase (MAPK). The release of cytokines and chemokines [tumour necrosis factor, interleukin (IL)-1 beta, IL-6, IL-8, IL-10, IL-12p70] into culture supernatants was measured with cytometric bead array. For unstimulated cells there were no differences in frequency of the monocytic subsets or their Toll-like receptor levels between allergic and non-allergic children. However, monocytes from allergic children had a significantly lower up-regulation of Toll-like receptor 2 upon peptidoglycan stimulation. Further, monocytes from allergic children had a higher spontaneous production of IL-6, but there were no differences between the two groups regarding p38-MAPK activity or cytokine and chemokine production upon stimulation. The allergic subjects in this study have a monocytic population that seems to display a hyporesponsive state as implicated by impaired regulation of Toll-like receptor 2 upon peptidoglycan stimulation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Case-Control Studies
  • Cells, Cultured
  • Child, Preschool
  • Female
  • Flow Cytometry
  • Humans
  • Hypersensitivity / immunology
  • Hypersensitivity / metabolism*
  • Immunity, Innate
  • Immunoglobulin E / blood
  • Interleukin-6 / immunology
  • Lipopolysaccharide Receptors / analysis
  • Lipopolysaccharides / pharmacology
  • Male
  • Monocytes / metabolism*
  • Peptidoglycan / pharmacology
  • Receptors, IgG
  • Signal Transduction / physiology*
  • Skin Tests
  • Toll-Like Receptor 2 / analysis
  • Toll-Like Receptor 2 / metabolism*
  • Toll-Like Receptor 4 / analysis
  • Toll-Like Receptor 4 / metabolism

Substances

  • Interleukin-6
  • Lipopolysaccharide Receptors
  • Lipopolysaccharides
  • Peptidoglycan
  • Receptors, IgG
  • Toll-Like Receptor 2
  • Toll-Like Receptor 4
  • Immunoglobulin E