Asthma is characterized by both local infiltration of eosinophils in the bronchial mucosa and bronchial hyperreactivity (BHR). A detailed characterization of BHR implies analysis of a histamine or methacholine dose-response curve yielding not only the dose at 20% fall of baseline forced expiratory volume in 1 s (FEV₁), but also a plateau (P) representing the maximal narrowing response in terms of percent change in FEV₁ and reactivity as the steepest slope at 50% of P (%FEV₁/doubling dose). In the baseline condition, the specific airway conductance (sGaw) may be considered closely related to airway lumen diameter. In 20 nonsmoking asthmatic patients, methacholine dose-response curves were obtained, and a sigmoid model fit yielded the BHR indexes. Immunohistochemistry with the monoclonal antibodies (EG₁ and EG₂) was used to recognize the total number of eosinophils and activated eosinophils, respectively. The number of activated eosinophils was significantly correlated to both P (r = 0.62; P < 0.05) and sGaw (r = 0.52; P < 0.05), whereas weaker and nonsignificant correlations were found for dose at 20% fall of baseline FEV₁ and the total number of eosinophils. We conclude that the number of activated eosinophils can be considered a marker of the inflammation-induced decrease of airway lumen diameter as represented by the plateau index and sGaw.

bronchial mucosa; bronchial hyperreactivity; methacholine dose-response curve

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