Inclusion Criteria:

• Aged 18 to 50 years. Younger subjects are excluded due to greater concerns with respect to risks from radiation and bronchoscopy in children; older subjects due to greater risks of bronchoscopy.
• Mild to moderate persistent asthma (forced expiratory volume in 1 second [FEV1] greater than or equal to 70% predicted {Hankinson, 1999 #266}; PC20 less than or equal to 8 mg/ml) and currently using only short acting inhaled beta agonists as needed for control of asthma symptoms.

Exclusion Criteria:

• The use of the following medications will exclude subjects from entering the study:

  • Oral or parenteral steroids within 6 months
  • Inhaled corticosteroids within 3 months
  • Antileukotrienes, b-adrenergic blocking agents, inhaled cromolyn sodium or nedocromil, macrolide antibiotics, or investigational drugs within 1 month
  • Drugs or exposures which, in the opinion of the investigators, could influence study results
• Tobacco within 1 year or less than or equal to 5 pack years.
• Pregnant women, lactating women, or women of childbearing age not willing to take precautions to avoid becoming pregnant during the study.
• Subjects with upper respiratory infection or receiving an influenza vaccine within 6 weeks of the study.
• Subjects with a history of allergy or adverse reaction to inhaled beta agonists or methacholine.
• Subjects with clinically significant evidence of cardiovascular, central nervous system, endocrine, gastrointestinal, hematopoietic, hepatic, psychiatric, or respiratory (other than asthma) disease

Eligibility will be determined by an investigator using the above inclusion/exclusion criteria.

No subjects will be excluded based on race or gender. Subjects must be between 18 and 50 in order to avoid greater risks of bronchoscopy and, in those under 18, exposure to radiation. To avoid risks, women will not be enrolled if pregnant, lactating or of childbearing potential and unwilling to undertake appropriate precautions.