A comparison of the airway response to segmental antigen bronchoprovocation in atopic asthma and allergic rhinitis

Background: Patients with allergic asthma and those with allergic rhinitis (without asthma) share many immunopathologic features but differ in the presence of lower airway symptoms in response to antigen. Objectives: We sought to compare the airway inflammatory response to antigen in patients with atopic asthma and allergic rhinitis. Methods: Segmental bronchoprovocation with saline or ragweed antigen was performed in 9 patients with atopic asthma and 9 patients with allergic rhinitis without asthma. The antigen dose used in segmental bronchoprovocation was 10% of the dose that caused a 20% decrease in FEV1 in response to inhalation challenge. Bronchoalveolar lavage (BAL) was performed from the saline- and antigen-challenged segments at 5 minutes and 48 hours after challenge. BAL fluid was analyzed for cell count and differential, distribution of lymphocytes, and concentration of soluble factors (histamine, IL-5, matrix metalloproteinase 9, tissue inhibitor of metalloproteinase 1, and fibronectin). In addition, BAL cells were cultured ex vivo, and IL-5, IFN-gamma, and IL-10 generation was measured. Results: Antigen challenge led to similar patterns of cellular recruitment, mediator levels, and BAL cell cytokine generation in both groups; however, the dose of antigen required to promote comparable responses in the airway was significantly less in patients with asthma. Conclusion: These data suggest that the pattern of acute airway inflammation in response to allergen does not by itself explain antigen-induced lower airway obstruction and asthma symptoms. We speculate that other factors, such as increased airway sensitivity to allergen or preexisting airway injury and remodeling, might explain why patients with asthma and rhinitis differ in their clinical and physiologic response to antigen exposure.