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Lipopolysaccharide LPS-mediated soluble TNF receptor release and TNF receptor expression by monocytes. Role of CD14,

J F Leeuwenberg1, M A Dentener, W A Buurman

  • 1Department of Surgery, University of Limburg, Maastricht, The Netherlands.

Journal of Immunology (Baltimore, Md. : 1950)
|May 15, 1994
PubMed

Insights

Lipopolysaccharide (LPS) activates monocytes to release soluble tumor necrosis factor receptor 75 (sTNF-R75), a process influenced by CD14 and serum proteins like LPS binding protein (LBP). LPS also modulates TNF-R expression, suggesting a mechanism for controlling TNF activity.

Area of Science:

  • Immunology
  • Cell Biology

Background:

  • Soluble tumor necrosis factor receptors (sTNF-R55 and sTNF-R75) are released by monocytes and their release is enhanced upon activation.
  • Lipopolysaccharide (LPS) is a key activator of monocytes.

Purpose of the Study:

  • To investigate the effect of LPS on the release of sTNF-R by monocytes.
  • To explore the roles of CD14, serum proteins, LPS binding protein (LBP), and bactericidal/permeability-increasing protein (BPI) in LPS-induced sTNF-R release and TNF-R expression.

Main Methods:

  • Monocyte activation with LPS.
  • Measurement of sTNF-R release.
  • Experiments using anti-CD14 monoclonal antibodies (mAbs).
  • Assessment of sTNF-R release under serum-free conditions with and without LBP or BPI.
  • Analysis of cell surface TNF-R expression modulation by LPS, LBP, and BPI.

Main Results:

  • LPS significantly enhanced sTNF-R75 release, but minimally affected sTNF-R55 release.
  • CD14 acts as an intermediate in LPS-induced sTNF-R75 release.
  • Serum proteins enhance LPS-induced sTNF-R75 release; LBP enhances it in serum-free conditions, while BPI inhibits it.
  • LPS caused rapid down-modulation of cell surface TNF-R55 and TNF-R75 expression, followed by enhanced re-expression.
  • LBP increased LPS-induced down-modulation, whereas BPI counteracted it.

Conclusions:

  • LPS-induced sTNF-R75 release and modulation of TNF-R expression represent a physiological mechanism to regulate TNF activity.
  • The findings highlight the complex interplay between LPS, its binding proteins, and monocyte receptors in controlling the inflammatory response.

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