Granulocyte-macrophage Colony-Stimulating Factor Modulates Lipopolysaccharide (LPS)-binding and LPS-response of Human Macrophages: Inverse Regulation of Tumour Necrosis Factor-Alpha and interleukin-10

Immunology. 1999 Dec;98(4):491-6. doi: 10.1046/j.1365-2567.1999.00904.x.

Abstract

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a well-known stimulus for the activation, differentiation and survival of monocytes (MO). Up to now most investigations focused on the short-term effects of GM-CSF. In this study we investigated the effects of GM-CSF on the long-term differentiation of human MO in the presence of serum. We found that MO-derived macrophages (Mphi) cultured with serum plus GM-CSF (GM-Mphi) were different from control Mphi (SER-Mphi) in terms of lipopolysaccharide (LPS)-stimulated cytokine release: GM-Mphi showed an increased tumour necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) production, especially at lower LPS concentrations, but the secretion of IL-10 was diminished. In addition, GM-Mphi secreted TNF-alpha but not IL-6 and IL-10, spontaneously. The spontaneous TNF-alpha production was not due to LPS contamination as it could not be blocked by anti-CD14 antibody. Flow cytometry revealed, however, that the receptor for LPS, CD14, was up-regulated on GM-Mphi and those Mphi released twice as much soluble CD14 into the supernatant as compared with SER-Mphi. The higher CD14 expression also resulted in an enhanced LPS-binding capacity of GM-Mphi. Furthermore, the LPS-response of GM-Mphi could only be blocked by about fourfold higher concentration of anti-CD14 antibody compared with SER-Mphi. In summary, GM-CSF promotes the generation of a pro-inflammatory type of Mphi in two different ways: first, the down-regulation of autocrine IL-10 production increases the release of cytokines such as IL-6 and TNF-alpha and second, the up-regulation of membrane and soluble CD14 expression leads to a higher sensitivity towards LPS-stimulation.

MeSH terms

  • Antibodies, Monoclonal / pharmacology
  • Cell Differentiation / drug effects
  • Cells, Cultured
  • Flow Cytometry
  • Granulocyte-Macrophage Colony-Stimulating Factor / pharmacology*
  • Humans
  • Interleukin-10 / metabolism*
  • Interleukin-6 / metabolism
  • Lipopolysaccharide Receptors / immunology
  • Lipopolysaccharides / pharmacology*
  • Macrophages / drug effects
  • Macrophages / immunology*
  • Protein Binding
  • Tumor Necrosis Factor-alpha / metabolism*

Substances

  • Antibodies, Monoclonal
  • Interleukin-6
  • Lipopolysaccharide Receptors
  • Lipopolysaccharides
  • Tumor Necrosis Factor-alpha
  • Interleukin-10
  • Granulocyte-Macrophage Colony-Stimulating Factor