Determinants of allergen-induced late bronchial responses in mild asthmatics

Study objective: To examine the baseline factors influencing the occurrence and magnitude of immediate- and late-phase responses in asthmatic patients after an allergen-induced bronchial provocation test (A-BPT). Design: Cross-sectional analysis in a homogenous group of 31 mild, Dermatop hagoides pteronyssinus-allergic patients with asthma. Setting: Allergy Department, Hospital Virgen del Camino, Pamplona, Spain. Interventions and measurements: Patients completed an asthma symptom questi onnaire and underwent skin tests, sputum induction, and methacholine bronch ial provocation test. The A-BPT was performed on a separate day. Sputum cel l profile and eosinophil cationic protein (ECP), tryptase, albumin, and int erleukin-5 levels were quantified in the entire sputum supernatant. Assays were done for eosinophils in blood, and/or ECP, and total and specific IgE levels in serum. Exposure to D pteronyssinus major allergens (Der p1 and De r 2) was measured by an assay based on monoclonal antibodies. Results: A-BPT findings were positive in all patients, and late-phase respo nses were detected in 29%. Late responders were exposed to higher levels of Der p1 (p = 0.028), had greater levels of ECP (p = 0.007) and albumin (p = 0.019) in sputum, and showed a trend toward higher lymphocyte numbers (p = 0.053) in sputum than isolated early responders. The allergen-induced prov ocative dose that induced a fall in FEV1 values greater than or equal to 20 % from the postdiluent values correlated with bronchial hyperresponsiveness (r = 0.36). The late-phase response magnitude correlated with Der pi expos ure (r = 0.49) and showed a trend toward correlation with sputum ECP levels (r = 0.38). Conclusion: Factors involved in the development of allergen-induced immedia te- and late-phase responses are different. Allergen natural exposure might prime the infiltration of the airway by activated inflammatory cells enhan cing the appearance and the severity of late-phase responses.