Increased Numbers of Both Airway Basophils and Mast Cells in Sputum after Allergen Inhalation Challenge of Atopic Asthmatics

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Abstract
Mast cells and basophils are metachromatic cells that participate in allergic inflammation. Allergen challenge to the airways of atopic asthmatic individuals increases levels of metachromatic cells, which may reflect an increase in mast cells, basophils, or both. We conducted a study to characterize the kinetics of basophil and mast cell recruitment to the airways of atopic asthmatic subjects after allergen inhalation challenge, using monoclonal antibodies specific for each type of cell. Of 19 subjects, 14 developed both early- and late-phase asthmatic responses (dual responders [DRs]), whereas five developed only early asthmatic responses (early responders [ERs]) after allergen inhalation. There was a significant increase in the number of sputum eosinophils (p < 0.002) and basophils (p < 0.002) at 7 h and 24 h after challenge in both ERs and DRs. There was also a significant increase in the number of activated eosinophils (p = 0. 00002) and mast cells (p = 0.009) in sputum at 7 h and 24 h after challenge in DRs, but not in ERs (p > 0.4). DRs had a significantly higher number of allergen-induced sputum basophils than did ERs (p < 0.01), and sputum basophils correlated significantly with airway hyperresponsiveness (AHR) to methacholine at 24 h after challenge (r = 0.66, p = 0.002). DRs tended to have higher allergen-induced basophil levels than did ERs, which may contribute to the observed AHR.