The purpose of this study is to identify the causes of asthma that were not previously suspected, to better understand the effects of inhaled steroids on asthma and to identify new way to treat asthma. In order to take advantage of the most current scientific expertise, we (scientists at UCSF) plan to work together with Genentech Inc. We believe that working with Genentech will provide the best chance of developing new treatments for asthma.