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Neutrophil secretion products regulate anti-bacterial activity in monocytes and macrophages

O Soehnlein1, E Kenne, P Rotzius

  • 1Department of Physiology and Pharmacology, Karolinska Institute, Stockholm, Sweden. oliver.sohnlein@ki.se

Clinical and Experimental Immunology
|November 10, 2007
PubMed

Insights

Neutrophil granule proteins enhance macrophage antimicrobial activity by increasing bacterial phagocytosis and reactive oxygen species (ROS) production. These findings reveal novel microbicidal roles for neutrophil proteins, suggesting potential anti-microbial therapy applications.

Area of Science:

  • Immunology
  • Cell Biology
  • Microbiology

Background:

  • Macrophages are key innate immune cells for bacterial clearance.
  • Neutrophils release granule proteins during acute inflammation.
  • The role of neutrophil granule proteins in macrophage antimicrobial activity is not well understood.

Purpose of the Study:

  • To investigate the novel role of neutrophil-derived granule proteins in enhancing macrophage anti-microbial functions.
  • To determine the effects of neutrophil secretion on bacterial phagocytosis and intracellular killing by monocytes and macrophages.

Main Methods:

  • Stimulation of neutrophils to induce secretion (antibody cross-linking of CD18 or fMLP treatment).
  • Incubation of monocytes and macrophages with neutrophil secretions.
  • Measurement of bacterial phagocytosis, intracellular calcium (Ca2+) levels, and reactive oxygen species (ROS) formation.

Main Results:

  • Neutrophil secretions significantly increased bacterial phagocytosis by monocytes and macrophages.
  • Secretions induced rapid monocyte and macrophage activation, evidenced by increased cytosolic free Ca2+.
  • Polymorphonuclear cell (PMN) secretions enhanced intracellular ROS formation, indicating increased bacterial killing.

Conclusions:

  • Neutrophil granule proteins activate macrophages, enhancing their capacity for bacterial phagocytosis and ROS production.
  • These findings suggest novel microbicidal properties of PMN granule proteins.
  • Neutrophil granule proteins show potential for development into anti-microbial therapies.

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