EOSINOPHIL INFILTRATION PRECEDES DEVELOPMENT OF AIRWAY HYPERREACTIVITY AND MUCOSAL EXUDATION AFTER INTRANASAL ADMINISTRATION OF INTERLEUKIN-5 TO MICE

Recently, we demonstrated that antibody to interleukin-5 (IL-5) preven ts the infiltration of eosinophils in the respiratory airways and the development of bronchial hyperreactivity in an animal model of allergi c asthma. In this study we investigated the influence of long-term int ranasal administration of IL-5 on airway responsiveness in vitro, the infiltration of inflammatory-leukocytes, and mucosal exudation. Mice ( BALB/c) received 1 mu g of recombinant human IL-5 in 30 mu l of saline solution or vehicle alone twice a day for 1, 3, and 7 days. At 3 and 7 days after IL-5 administration, the number of bronchoalveolar lavage eosinophils increased approximately fourfold and sixfold, respectivel y. Blood eosinophil numbers showed a similar increase. In addition 7 d ays after IL-5 treatment, total lung eosinophil peroxidase activity wa s significantly increased by 170% as compared with controls. The maxim al responsiveness of the trachea in vitro to methacholine was signific antly increased by 34%, as compared with controls, only at 7 days afte r IL-5 administration. Furthermore, mucosal exudation was also only in creased significantly at 7 days after IL-5 administration. It can be c oncluded that the IL-5-induced eosinophil infiltration precedes the de velopment of airway hyperreactivity and mucosal exudation.