15-LIPOXYGENASE IMMUNOREACTIVITY IN NORMAL AND IN ASTHMATIC AIRWAYS

Products of the 15-lipoxygenase (15-LO) pathway of arachidonic acid me tabolism such as the mono- and di-hydroxyeicosatetraenoic acids (HETEs ) may contribute to the pathophysiology of allergic airway inflammatio n through the recruitment and activation of inflammatory cells and sti mulation of glandular secretion. In this study we have examined the ex pression of 15-LO and its cellular localization in the asthmatic and n ormal bronchial mucosa. Bronchial mucosal biopsies were obtained by fi beroptic bronchoscopy from 10 patients with symptomatic allergic asthm a and six normal control subjects and processed into glycolmethacrylat e resin. Sections 2 mu m thick were immunostained using a specific rab bit polyclonal antihuman 15-LO antibody. Strong immunoreactivity for 1 5-LO was present throughout the epithelium in both the asthmatic and t he normal subjects, with no difference between the two groups. Cells e xpressing 15-LO immunoreactivity were also present in the submucosa of both groups, with a significantly greater number present in the asthm atic group (median, 15.3 cells/mm(2)) than in the normal group (median , 6.9 cells/mm(2)) (p = 0.01). The majority (85%) of the submucosal 15 -LO(+) cells were eosinophils. Patchy 15-LO immunoreactivity was also seen in the vascular endothelium in both groups. These findings demons trated increased 15-LO expression in the bronchial submucosa of asthma tic subjects, and they suggest that 15-LO products in asthma originate from both bronchial epithelium and infiltrating eosinophils.