Demonstration of bronchial eosinophil activity in seasonal allergic rhinitis by induced plasma exudation combined with induced sputum

Background-Patients with seasonal allergic rhinitis may develop bronchial h yperresponsiveness during the active disease period. Eosinophil activation may occur in the bronchial mucosa and may be reflected by increased sputum levels of eosinophil cationic protein (ECP), especially when ECP binding pr oteins such as alpha(2)-macroglobulin pass through the lamina propria and a cross the epithelium into the airway lumen. A study was therefore undertake n to determine histamine airway responsiveness (FEV1) and bronchovascular r esponsiveness (exudation of alpha(2)-macroglobulin) to histamine in subject s with seasonal allergic rhinitis, and to explore whether sputum ECP levels are increased by the use of induced exudation followed by induced sputum. Method-Eleven patients with seasonal allergic rhinitis were examined before and during a birch pollen season. Sputum was induced by inhalation of 4.5% saline twice before and twice during the pollen season. Histamine inhalati ons were given before the second of each pair of sputum inductions at incre asing concentrations until FEV1 was reduced by 20%. Sputum levels of alpha( 2)-macroglobulin and ECP were determined as indices of bronchial exudation of plasma and activation of bronchial eosinophils, respectively. Results-Bronchomotor responsiveness increased during the pollen season (med ian difference in the reduction of FEV1 9% (95% confidence interval (CI) -3 to 26)) but histamine induced exudation of plasma was not increased. Basel ine sputum levels of alpha(2)-macroglobulin and ECP did not increase. Hista mine induced exudation of alpha(2)-macroglobulin was associated with increa sed sputum levels of ECP exclusively during the pollen season (median diffe rence 8.2 ng/ml (95% CI 0.4 to 562.0)). Conclusion-Bronchial hyperresponsiveness in seasonal allergic rhinitis may not be associated with bronchovascular exudative hyperresponsiveness, Sputu m levels of ECP were increased only during the season, and only after induc ed exudation (potentially moving ECP to the mucosal surface). It is suggest ed that the combined method of induced exudation and induced sputum may sig nificantly improve the yield of some markers of inflammation in sputum samp les.