Role of Airway Eosinophilia and Eosinophil Activation in Sephadex-induced Inflammation

The effects of an intravenous injection of Sephadex beads on lung eosinophil infiltration and eosinophil peroxydase activity and its relationship to bronchial hyperresponsiveness was examined in guinea pigs. This Sephadex beads injection led to blood, lung and airway eosinophilia in association with bronchial hyperresponsiveness. Histologic examination of the lower bronchus indicated that the eosinophil number increased markedly in the mucosa and submucosa. In addition, the eosinophils surrounding the bronchioles 1 day after the Sephadex injection migrated further in airway submucosa and mucosa 7 and 14 days after. Moreover, the bronchial hyperresponsiveness is observed without histologic evidence of airway epithelium damage. Therefore, the bronchial hyperresponsiveness seems to be more related to the eosinophil infiltration in the airway epithelium and possibly eosinophil activation rather than to the eosinophil number recovered in the BAL fluid. We conclude that the maintenance of hyperresponsiveness state could be associated with the persistence of blood and airway eosinophilia.