 The goal of this study is to identify the immunological factors that influence a patients response to the presence of the fungus Aspergillus fumigatus A. fumigatus in the lungs. In patients with cystic fibrosis CF, this fungus is not known to cause damage to the lungs, but some patients respond with an allergic reaction that may cause wheeze, cough, or difficulty breathing. Approximately 230 patients will be enrolled with an additional 60 people who do not have CF and who do not have a history of asthma to serve as a comparison group. 