摘要：

present and activated in the airway lumen and tissue 1 of patients with current asthma, that the cells are increased in number when asthma is uncontrolled or severe 2 and decreased in number when asthma is controlled, 3 and that treatment strategies that aim to control airway eosinophilia are significantly more effective and less expensive in improving asthma control 4 and decreasing asthma exacerbations compared with guideline-based clinical strategies. Cynicism was fuelled by observations that in murine models of allergic sensitization airway hyperresponsiveness could be induced without eosinophils. 5 Skepticism grew stronger when therapy with mAbs against IL-5, which has no known clinically relevant biologic activity other than on eosinophils, did not result in improvement in asthma outcomes despite decreasing airway and blood eosinophil numbers. 6,7 A major reason for the failure of the early anti㊣L-5 clinical trials was that the patients recruited into the studies were not identified to have a predominantly eosinophil-driven disease. 8 Traditionally, treatment decisions are made on the basis of patient-reported symptoms or measures of airflow or airway hyperresponsiveness. The cellular nature of inflammation is not often identified, although quantitative cell counts in sputum provide a reliable and relatively noninvasive method to assess bronchitis. Sputum examination has identified cellular heterogeneity in asthmatic patients in routine clinical practice 9 and in patients recruited into clinical trials. 10 The importance of careful phenotyping and the relevance of eosinophils in asthmatic patients were confirmed by the demonstration of the efficacy of anti㊣L-5 mAb therapy in patients with asthma who had consistently increased eosinophil counts in sputum of greater than 2.5% to 3% on at least 2 occasions. 11

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