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, Dermatophagoides pteronyssinus-allergic patients with asthma. SETTING Allergy Department, Hospital Virgen del Camino, Pamplona, Spain. INTERVENTIONS AND MEASUREMENTS Patients completed an asthma symptom questionnaire and underwent skin tests, sputum induction, and methacholine bronchial provocation test. The A-BPT was performed on a separate day. Sputum cell profile and eosinophil cationic protein (ECP), tryptase, albumin, and interleukin-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 Der 2) was measured by an assay based on monoclonal antibodies. RESULTS A-BPT findings were positive in all patients, and late-phase responses 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 provocative dose that induced a fall in FEV(1) values > or =20% from the postdiluent values correlated with bronchial hyperresponsiveness (r = 0.36). The late-phase response magnitude correlated with Der p1 exposure (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 immediate- and late-phase responses are different. Allergen natural exposure might prime the infiltration of the airway by activated inflammatory cells enhancing the appearance and the severity of late-phase responses.