Asthma affects millions of people worldwide has been gaining prevalence in the U.S. Symptoms of allergic asthma include airway inflammation, increased numbers of eosinophils in BAL and sputum, and airways hyper responsiveness. While the role of eosinophils in regulating the development and/or symptoms of allergic asthma is controversial, it is clear that they play some role in this disease. A proper understanding of the role of these cells in modulating the development and/or severity of allergic asthma will allow us to have an impact on this disease. Our long-range goal is to provide a detailed understanding of the role of eosinophils in allergic airway responses. The objective of this application is to determine eosinophil functions that may modulate the development of airway inflammation and airways hyperresponsiveness during allergic airway responses. The proposed experiments arose from our preliminary data and are driven by a central hypothesis, that eosinophils modulate airway production of chemokines, altering T cell recruitment to the lung and elaboration of their effector function during the development of allergic airway inflammation. Our rationale is that a better understanding of the role of eosinophil function in this disease will provide us with information needed to treat diseases such as allergies and asthma. We plan 3 specific aims: 1) determine the role of eosinophils in inducing airway inflammation and AHR during the development and maintenance of airway allergic responses, 2) determine whether eosinophil derived Th2 cytokines are required for the recruitment of CD4+ T cells into the lung and the development of allergic airway response; and 3) determine role of eosinophil derived factors in modulating the elaboration of Th2 effector function during airway allergic responses. The proposed work is innovative, and we are well poised to conduct these studies because we will be taking advantage of knockout and transgenic mouse models to perform these experiments. We expect that our approach will identify the role of eosinophils in modulating the development of airway inflammation and airways hyperresponsiveness. The data generated from this application will have a significant impact on human health, as we expect to provide information on the molecular pathology of asthma, and on potential targets within eosinophils that may be used to manipulate their functions involved in asthma.