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Macrophages acquire neutrophil granules for antimicrobial activity against intracellular pathogens

Belinda H Tan1, Christoph Meinken, Max Bastian

  • 1Department of Microbiology, Immunology, and Molecular Genetics, David Geffen School of Medicine, University of California, Los Angeles, CA 90095, USA.

Journal of Immunology (Baltimore, Md. : 1950)
|July 20, 2006
PubMed

Insights

Neutrophils transfer antimicrobial peptides to macrophages, enhancing the immune response against intracellular pathogens like Mycobacterium tuberculosis. This cooperative defense strategy boosts macrophage antimicrobial activity.

Area of Science:

  • Immunology
  • Cell Biology
  • Microbiology

Background:

  • Macrophages are key targets for intracellular pathogens.
  • Neutrophils possess antimicrobial agents in their granules, but their role against intracellular pathogens was unclear.

Purpose of the Study:

  • To elucidate the mechanism by which neutrophils mediate antimicrobial activity against intracellular pathogens, specifically Mycobacterium tuberculosis.
  • To investigate the role of neutrophil granules and apoptotic neutrophils in combating intracellular mycobacterial infections.

Main Methods:

  • Demonstration of growth inhibition of extracellular mycobacteria by apoptotic neutrophils and purified granules.
  • Assessment of intracellular M. tuberculosis viability following macrophage phagocytosis of apoptotic neutrophils.
  • Tracking of granule contents' trafficking and colocalization with mycobacteria within macrophages.

Main Results:

  • Apoptotic neutrophils and their purified granules inhibited extracellular mycobacterial growth.
  • Macrophage phagocytosis of apoptotic neutrophils led to decreased viability of intracellular M. tuberculosis.
  • Uptake of purified neutrophil granules alone also reduced intracellular mycobacterial growth.
  • Neutrophil granule contents trafficked to early endosomes and colocalized with intracellular mycobacteria.

Conclusions:

  • Transfer of antimicrobial peptides from neutrophils to macrophages constitutes a cooperative innate immune defense mechanism against intracellular pathogens.
  • This neutrophil-macrophage interaction complements other antimicrobial peptide delivery pathways.
  • The findings provide a novel understanding of host defense against Mycobacterium tuberculosis.

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