Mild allergic asthma subjects receive three times an infusion containing 750 mg of mepolizumab. Two weeks after the third infusion, subjects will be experimentally infected with RV16. One day before and six days after infection a bronchoscopy will be performed to collect bronchoalveolar lavage fluid and bronchial brushes. Blood will be collected at each infusion and each bronchoscopy and at least 6 weeks after infection. Lung function will be evaluated throughout the study.