Subjects with mild and moderate asthma respond to segmental allergen challenge with similar, reproducible, allergen-specific inflammation

Background: The relationship between severity of asthma and bronchial inflammation is poorly understood. Objective: We examined acute and subacute inflammatory responses to allergen in subjects with mild and moderate persistent asthma to evaluate whether different cellular and mediator responses to endobronchial allergen challenge are associated with differences in disease severity. Methods: Segmental allergen challenge was performed in 8 subjects with mild and 10 subjects with moderate allergic asthma to compare baseline airways inflammation and allergen-induced inflammatory responses 24 hours later. This evaluation was repeated after 6 weeks in 9 subjects to investigate the reproducibility of these inflammatory responses. Results: Subjects with mild and moderate asthma had similar decreases in FEV₁ in response to segmental allergen challenge (9.1% ± 4.2% vs 15.1% ± 4.6%, P = .35). There was no difference in inflammatory cell counts or cytokine concentrations in the groups with mild and moderate asthma at baseline or after saline or allergen challenge. Repeat segmental allergen challenge 6 weeks later showed that these cellular and cytokine responses were reproducible. Conclusion: Segmental allergen challenge in subjects with mild and moderate asthma produces similar allergen-specific physiologic and inflammatory responses that are reproducible 6 weeks later. In this model of allergic asthma, acute responses to allergen do not appear to be related to disease severity.