title: Differential interleukin-10 and gamma interferon mRNA expression in lungs of cilium-associated respiratory bacillus-infected mice.
abstract: The cilium-associated respiratory (CAR) bacillus is a gram-negative, extracellular bacterium that causes persistent respiratory tract infections in rodents. We have previously demonstrated that BALB/c mice are more susceptible to CAR bacillus-induced disease than resistant C57BL/6 mice, with elevations in pulmonary gamma interferon (IFN-gamma) and interleukin (IL)-4. IL-10 is a type 2 cytokine that can increase host susceptibility to bacterial diseases through its anti-inflammatory effects, including suppression of macrophage function. The purpose of this study was to further describe the cytokine profiles associated with histologic lesions in CAR bacillus-infected mice and to assess the effects of cytokine depletion on the pathogenesis of disease. Six-week-old female BALB/c and C57BL/6 mice and mice with targeted mutations in IFN-gamma and IL-4 were inoculated intratracheally with 10(5) CAR bacillus organisms, and samples were collected at 6 to 7 weeks postinoculation. Lung samples were collected for histopathologic examination and analysis of cytokine mRNA. IFN-gamma, IL-10, and IL-4 mRNA levels in the lungs of infected mice were semiquantitatively measured using a reverse transcriptase-mediated PCR assay and compared to those in uninfected control animals of each strain. BALB/c mice infected with CAR bacillus had a median lung lesion score of 6 and IL-10 and IL-4 mRNA levels were significantly elevated. The majority of C57BL/6 mice were resistant to disease characterized by lung lesions scores of 2 or less and a dominant IFN-gamma mRNA cytokine profile. A few C57BL/6 mice with lesions scores of 5 or greater had elevations in all three cytokines and were susceptible to disease. C57BL/6 IFN-gamma knockout mice had increased disease with elevations in IL-10 and IL-4 mRNA, while BALB/c IL-4 knockout mice infected with CAR bacillus had a mild decrease in lesion severity and an attenuated IL-10 mRNA expression compared to wild-type BALB/c mice. These data indicate that IL-10 and IL-4 predominate in CAR bacillus-induced histologic lesions in mice, while IFN-gamma may play a role in resistance to disease.
authors.affiliation: Department of Veterinary Pathobiology, University of Missouri-Columbia, 65211, USA. lvkendall@ucdavis.edu
authors.forename: L V
authors.initials: LV
authors.lastname: Kendall
authors.forename: L K
authors.initials: LK
authors.lastname: Riley
authors.forename: R R
authors.initials: RR
authors.lastname: Hook
authors.forename: C L
authors.initials: CL
authors.lastname: Besch-Williford
authors.forename: C L
authors.initials: CL
authors.lastname: Franklin
mesh_terms: D000818:Animals; D004198:Disease Susceptibility; D005260:Female; D006090:Gram-Negative Bacteria / Q000276:immunology*; D016905:Gram-Negative Bacterial Infections / Q000276:immunology* / Q000382:microbiology / Q000503:physiopathology; D007371:Interferon-gamma / Q000235:genetics / Q000378:metabolism*; D016753:Interleukin-10 / Q000235:genetics / Q000378:metabolism*; D008168:Lung / Q000276:immunology* / Q000382:microbiology; D051379:Mice; D008807:Mice, Inbred BALB C; D012333:RNA, Messenger / Q000378:metabolism*; D012141:Respiratory Tract Infections / Q000276:immunology / Q000382:microbiology / Q000503:physiopathology; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D012333:RNA, Messenger; D016753:Interleukin-10; D007371:Interferon-gamma