Dynamics of eosinophil infiltration in the bronchial mucosa before and after the late asthmatic reaction

We wanted to determine whether changes in bronchial hyperresponsiveness (BHR) following allergen challenge show a time relationship with inflammatory events in the airways of allergic asthmatic subjects. Lavage was performed and endobronchial biopsies were taken via the fiberoptic bronchoscope, before, and 3 and 24 h after, allergen challenge, on separate occasions, in nine dual asthmatic responders. The numbers of activated eosinophils, identified by immunohistochemistry, using the monoclonal anti-eosinophil cationic protein antibody, EG2, were significantly increased both at 3 h and at 24 h in the submucosa and bronchial lavage. A significant negative correlation was found between the number of EG2+ cells in the submucosa and in the bronchial lavage 24 h after the allergen challenge (r = -0.70). At 24 h, the amount of eosinophil cationic protein (ECP) was increased in the bronchial lavage. A significant correlation was observed between the amount of ECP at 3 h and the log provocative dose of house dust mite producing a 20% fall in forced expiratory volume in one second (PD20 HDM) (r = -0.63). The results suggest a recruitment of activated eosinophils to the submucosa and, further, to the epithelial lining, followed by degranulation. This process has already started 3 h after allergen challenge, and lasts for at least 24 h, which may result in mucosal damage and subsequent allergen-induced increase in BHR, before and after the late asthmatic reaction.