Differential effect of inhibiting MD-2 and CD14 on LPS- versus whole E. coli bacteria-induced cytokine responses in human blood

Adv Exp Med Biol. 2012;946:237-51. doi: 10.1007/978-1-4614-0106-3_14.

Abstract

Background: Sepsis is a major world-wide medical problem with high morbidity and mortality. Gram-negative bacteria are among the most important pathogens of sepsis and their LPS content is regarded to be important for the systemic inflammatory reaction. The CD14/myeloid differentiation factor 2 (MD-2)/TLR4 complex plays a major role in the immune response to LPS . The aim of this study was to compare the effects of inhibiting MD-2 and CD14 on ultra-pure LPS - versus whole E. coli bacteria-induced responses.

Methods: Fresh human whole blood was incubated with upLPS or whole E. coli bacteria in the presence of MD-2 or CD14 neutralizing monoclonal antibodies, or their respective controls, and/or the specific complement-inhibitor compstatin. Cytokines were measured by a multiplex (n = 27) assay. NFκB activity was examined in cells transfected with CD14, MD-2 and/or Toll-like receptors.

Results: LPS-induced cytokine response was efficiently and equally abolished by MD-2 and CD14 neutralization. In contrast, the response induced by whole E. coli bacteria was only modestly reduced by MD-2 neutralization, whereas CD14 neutralization was more efficient. Combination with compstatin enhanced the effect of MD-2 neutralization slightly. When compstatin was combined with CD14 neutralization, however, the response was virtually abolished for all cytokines, including IL-17, which was only inhibited by this combination. The MD-2-independent effect observed for CD14 could not be explained by TLR2 signaling.

Conclusion: Inhibition of CD14 is more efficient than inhibition of MD-2 on whole E. coli-induced cytokine response, suggesting CD14 to be a better target for intervention in Gram-negative sepsis, in particular when combined with complement inhibition.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.
  • Review

MeSH terms

  • Escherichia coli / immunology*
  • Escherichia coli Infections / blood
  • Escherichia coli Infections / immunology*
  • Humans
  • Lipopolysaccharide Receptors / immunology*
  • Lipopolysaccharide Receptors / metabolism
  • Lipopolysaccharides / pharmacology
  • Lymphocyte Antigen 96 / immunology*
  • Lymphocyte Antigen 96 / metabolism
  • Sepsis / immunology*
  • Sepsis / metabolism

Substances

  • LY96 protein, human
  • Lipopolysaccharide Receptors
  • Lipopolysaccharides
  • Lymphocyte Antigen 96