The Development of Pulmonary Fibrosis in a Murine Model of Experimental Hypersensitivity Pneumonitis Is Not Associated with a Dominant Th2 Adaptive Response
MM Kelly, B Atkinson, L Maxwell, C Gwozd, P Kubes. University of Calgary, Calgary, AB, Canada
Background: Hypersensitivity pneumonitis (HP) is an inflammatory interstitial lung disease caused by repeated inhalation of a wide variety of antigens, with 5% developing chronic fibrosis and respiratory failure. Chronic HP is recognized as being a cause of a usual interstitial pneumonia pattern of fibrosis, with a peripheral distribution of collagen deposition. A murine model of experimental HP (EHP) involves repeated exposure to antigens from Saccharopolyspora Rectivirgula (SR Ag), the main causative agent of Farmer's Lung. Studies with this model suggest that the adaptive immune response is skewed towards a Th1 (high IFN-) environment. A generally held paradigm is that fibrosis is suppressed by a Th1 environment and promoted by a Th2 (high IL-4) environment. We hypothesized that the development of fibrosis would be accompanied by increasing concentrations of Th2 type cytokines. The aim of this study was to establish a robust model of pulmonary fibrosis in EHP and to examine the immune-mediated mechanisms involved in the development of chronic fibrosis.
Design: C57BL/6 mice were exposed to SR Ag for 3 D/wk. A precise dose of SR Ag was administered by the use of a microsprayer device and aerosolizer. Mice were harvested at the end of weeks 1-3, 5 and 6, when lungs were inflated and fixed in formalin, processed to paraffin and sections cut and stained with H&E and picrosirius red (PSR). Bronchoalveolar lavage (BAL) fluid was stored for subsequent measurement of cytokines using multiplexing xMAP technology.
Results: Sustained pulmonary inflammation developed by 2 weeks of SR Ag exposure, with bronchial associated lymphoid tissue (BALT) and airway goblet cell epithelial metaplasia. By the 3rd week, peripheral pulmonary fibrosis was present identified by PSR staining viewed under polarized light. These changes persisted at least until the 6th week, the longest timepoint examined. Concentrations of Th1 (IFN-, IP-10, IL-12) and Th2 (IL-4, IL-13, IL-5) mediators in BAL fluid were not significantly different between timepoints and neither showed dominance.
Conclusions: We have demonstrated a valid model of EHP with many of the characteristics of chronic HP in humans (BALT, airway goblet cell metaplasia, peripheral fibrosis). We found no evidence of Th1 or Th2 dominance at any timepoint examined, at least with regard to measurements in BAL fluid.
Monday, March 9, 2009 1:00 PM
Poster Session II # 235, Monday Afternoon