Interferon-γ Production by Neutrophils during Bacterial Pneumonia in Mice

Center for Airways Disease, Department of Medicine, University of North Carolina, Chapel Hill, NC 27599-7248, USA.
American Journal of Respiratory and Critical Care Medicine (Impact Factor: 13). 12/2010; 183(10):1391-401. DOI: 10.1164/rccm.201004-0592OC
Source: PubMed


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.
To examine the expression and function of IFN-γ in bacterial pneumonias.
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.
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.
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.

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    • "Interferon-γ has been shown to modulate many aspects of in vitro neutrophil functions [41] [42] [43]. Williams et al. [44] showed that IFN-γ protects against the development of structural damage in experimental arthritis by regulating neutrophil influx into diseases joints and in vitro studies using fibroblast-like synoviocytes, IFN-γ modulated both IL-1β and TNF-α, resulting in the down-regulation of chemokine CXCL-8. "
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    • "Reduced levels of TNF-α, IL-1β and IL-6 have been associated with improved clearance of pulmonary staphylococci and survival [11]. IL-10 inhibits cytokine production by macrophages [12] and IFN-γ and IL-12 can promote phagocytic uptake and killing of S. aureus by immune dells [13]–[15]. "
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