Interleukin-18 primes the oxidative burst of neutrophils in response to formyl-peptides: role of cytochrome b558 translocation and N-formyl peptide receptor endocytosis

Clin Diagn Lab Immunol. 2005 Mar;12(3):436-46. doi: 10.1128/CDLI.12.3.436-446.2005.


Using flow cytometry, we observed that interleukin-18 (IL-18) primed human neutrophils (PMNs) in whole blood to produce superoxide anion (O2 degrees-) in response to N-formyl peptide (fMLP) stimulation, whereas IL-18 alone had no significant effect. In contrast to tumor necrosis factor alpha (TNF-alpha), which is a cytokine known to strongly prime O2 degrees- production, IL-18 did not induce either p47phox phosphorylation or its translocation from the cytosol to the plasma membrane. However, IL-18 increased PMN degranulation, as shown by increased levels of cytochrome b558 and CD11b expression at the PMN surface. Moreover, addition of IL-18 to whole blood for 45 min reduced the ability of PMNs to bind to fMLP, suggesting endocytosis of fMLP receptors, as visualized by confocal microscopy. 2,3-Butanedione 2-monoxime, which inhibits endosomal recycling of plasma membrane components back to the cell surface, concomitantly accentuated the diminution of fMLP binding at the PMN surface and increased IL-18 priming of O2 degrees- production by PMNs in response to fMLP. This suggests that fMLP receptor endocytosis could account, at least in part, for the priming of O2 degrees- production. In addition, genistein, a tyrosine kinase inhibitor, and SB203580, a p38 mitogen-activated protein kinase (p38MAPK) inhibitor, completely reversed the decreased level of fMLP binding and increased the level of CD11b expression after IL-18 treatment. Flow cytometric analysis of intact PMNs in whole blood showed that IL-18 increased p38MAPK phosphorylation and tyrosine phosphorylation. In particular, IL-18 induced phosphorylation of focal adhesion kinase (p125FAK), which has been implicated in cytoskeleton reorganization. Taken together, our findings suggest several mechanisms that are likely to regulate cytokine-induced priming of the oxidative burst in PMNs in their blood environment.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Degranulation / drug effects
  • Cells, Cultured
  • Cytochrome b Group / metabolism
  • Endocytosis / drug effects
  • Focal Adhesion Kinase 1
  • Focal Adhesion Protein-Tyrosine Kinases
  • Humans
  • Interleukin-18 / pharmacology*
  • N-Formylmethionine Leucyl-Phenylalanine / pharmacology
  • NADPH Oxidases / metabolism
  • Neutrophils / drug effects
  • Neutrophils / metabolism*
  • Phosphorylation / drug effects
  • Protein Transport
  • Protein-Tyrosine Kinases / metabolism
  • Receptors, Formyl Peptide / physiology*
  • Respiratory Burst / drug effects*
  • p38 Mitogen-Activated Protein Kinases / metabolism


  • Cytochrome b Group
  • Interleukin-18
  • Receptors, Formyl Peptide
  • N-Formylmethionine Leucyl-Phenylalanine
  • cytochrome b558
  • NADPH Oxidases
  • Protein-Tyrosine Kinases
  • Focal Adhesion Kinase 1
  • Focal Adhesion Protein-Tyrosine Kinases
  • PTK2 protein, human
  • p38 Mitogen-Activated Protein Kinases