Patients will be treated with imatinib in a randomized, double-blind, placebo controlled trial. Assessments will include methacholine and AMP reactivity, airway function, symptoms, airway wall thickness by CT scan, analysis of induced sputum, non-invasive markers of airway inflammation, and bronchoscopy including endobronchial biopsy and bronchoalveolar lavage - all before and at the end of therapy.