title: Differential effect of inhibiting MD-2 and CD14 on LPS- versus whole E. coli bacteria-induced cytokine responses in human blood.
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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Laboratory Medicine, Research Laboratory, Nordland Hospital, Bodø, Norway. Dorte.Christiansen@nlsh.no
authors.forename: D
authors.initials: D
authors.lastname: Christiansen
authors.forename: O L
authors.initials: OL
authors.lastname: Brekke
authors.forename: J
authors.initials: J
authors.lastname: Stenvik
authors.forename: J D
authors.initials: JD
authors.lastname: Lambris
authors.forename: T
authors.initials: T
authors.lastname: Espevik
authors.forename: T E
authors.initials: TE
authors.lastname: Mollnes
mesh_terms: D004926:Escherichia coli / Q000276:immunology*; D004927:Escherichia coli Infections / Q000097:blood / Q000276:immunology*; D006801:Humans; D018950:Lipopolysaccharide Receptors / Q000276:immunology* / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D051218:Lymphocyte Antigen 96 / Q000276:immunology* / Q000378:metabolism; D018805:Sepsis / Q000276:immunology* / Q000378:metabolism
chemical_list: C495377:LY96 protein, human; D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides; D051218:Lymphocyte Antigen 96