Background: The difference between allergen-induced asthma and exercise-induced asthma with respect to the late asthmatic response and airway responsiveness has not been well elucidated.
Objective: We compared the incidence of late asthmatic response, the changes in airway responsiveness, the degree of epithelial desquamation, and the activation of eosinophils in the airways after induction of allergen-induced asthma and exercise-induced asthma.
Methods: Allergen-induced asthma or exercise-induced asthma was provoked in asthmatic patients, and sputum was collected before challenge and at the immediate asthmatic response and the late asthmatic response. Clusters of columnar epithelial cells in sputum (Creola bodies) were detected to evaluate respiratory epithelial damage, and the sputum eosinophil cationic protein (ECP) concentration was measured to evaluate eosinophil activation in the airways. Airway responsiveness was measured before and 48 hours after the challenge.
Results: The maximal % fall in FEV1 with the late asthmatic response was significantly higher after induction of allergen-induced asthma than after exercise-induced asthma, even though the maximal % fall in FEV1 with the immediate asthmatic response was similar. Airway responsiveness increased significantly at 48 hours after allergen-induced asthma, while it did not change after exercise-induced asthma. The increase in airway responsiveness was not correlated with the maximal % fall in FEV1 with the late asthmatic response, but was correlated with the degree of epithelial damage evaluated by observation of Creola bodies. The sputum ECP concentration and the percentage of sputum eosinophils increased significantly with the late asthmatic response after allergen-induced asthma, but did not change after exercise-induced asthma.
Conclusions: We conclude that less airway inflammation was provoked by exercise-induced asthma resulting in less epithelial damage and no increase of airway responsiveness in contrast to allergen-induced asthma.