title: Interferon-γ production by neutrophils during bacterial pneumonia in mice.
abstract: BACKGROUND
  Neutrophils are usually the first circulating leukocytes to respond during bacterial pneumonia. Their expression of oxidants, proteases, and other mediators present in granules is well documented, but their ability to produce mediators through transcription and translation after migration to an inflammatory site has been appreciated only more recently. Interferon (IFN)-γ is a cytokine with many functions important in host defense and immunity.
  
  
  OBJECTIVE
  To examine the expression and function of IFN-γ in bacterial pneumonias.
  
  
  METHODS
  IFN-γ mRNA and protein were measured in digests of mouse lungs with 24-hour bacterial pneumonia. Bacterial clearance was studied with IFN-γ-deficient mice.
  
  
  RESULTS
  Streptococcus pneumoniae and Staphylococcus aureus each induce expression of IFN-γ mRNA and protein by neutrophils by 24 hours. Only neutrophils that have migrated into pneumonic tissue produce IFN-γ. Deficiency of Hck/Fgr/Lyn, Rac2, or gp91(phox) prevents IFN-γ production. IFN-γ enhances bacterial clearance and is required for formation of neutrophil extracellular traps. In contrast, Pseudomonas aeruginosa and Escherichia coli induce production of IFN-γ mRNA but not protein. During pneumonia induced by E. coli but not S. pneumoniae, neutrophils produce microRNAs that target the 3' untranslated region of the IFN-γ gene.
  
  
  CONCLUSIONS
  S. pneumoniae and S. aureus, but not P. aeruginosa and E. coli, induce emigrated neutrophils to produce IFN-γ within 24 hours. Hck/Fgr/Lyn, Rac2, and NADPH oxidase are required for IFN-γ production. IFN-γ facilitates bacterial clearance at least in part through regulating formation of neutrophil extracellular traps. Differential expression by neutrophils of microRNAs that target the 3' untranslated region of the IFN-γ gene may contribute to the pathogen-specific regulation of translation.
authors.affiliation: Center for Airways Disease, Department of Medicine, University of North Carolina, Chapel Hill, NC 27599-7248, USA.
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Yamada
authors.forename: John C
authors.initials: JC
authors.lastname: Gomez
authors.forename: Pauline E
authors.initials: PE
authors.lastname: Chugh
authors.forename: Clifford A
authors.initials: CA
authors.lastname: Lowell
authors.forename: Mary C
authors.initials: MC
authors.lastname: Dinauer
authors.forename: Dirk P
authors.initials: DP
authors.lastname: Dittmer
authors.forename: Claire M
authors.initials: CM
authors.lastname: Doerschuk
mesh_terms: D000818:Animals; D001992:Bronchoalveolar Lavage Fluid / Q000276:immunology; D002478:Cells, Cultured; D004195:Disease Models, Animal; D004797:Enzyme-Linked Immunosorbent Assay; D004926:Escherichia coli / Q000276:immunology; D007113:Immunity, Innate / Q000276:immunology; D007371:Interferon-gamma / Q000276:immunology*; D008168:Lung / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D009504:Neutrophils / Q000276:immunology*; D018410:Pneumonia, Bacterial / Q000276:immunology*; D011550:Pseudomonas aeruginosa / Q000276:immunology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013211:Staphylococcus aureus / Q000276:immunology; D013296:Streptococcus pneumoniae / Q000276:immunology
chemical_list: D007371:Interferon-gamma