Subjects must be between 18 and 55 years of age.
Negative pregnancy test within two days of the scan and willingness to adhere to reliable birth control until the completion of the protocol.
Subjects must be able to give informed consent.
Subjects in the negative control group must have no history of asthma or other lung disease.
Control subjects must have negative prick skin tests to the allergens used.
Asthmatic subjects must have asthma as defined in this study.
Asthmatic subjects must have positive prick skin tests to one or more allergens used.
Subjects must have access to a primary medical care provider outside of the NIH.
Subjects must weigh less than 136 kg.
No breast feeding.
No smoking in the last 3 years, or greater than 6 months of smoking in the past ten years.
No antihistamines one week prior to the skin test on the first visit.
No history of coronary artery disease.
No evidence of lung disease other than asthma; no evidence of autoimmune or inflammatory disease which could affect lung function such as lupus erythematosus (except for the control subjects with Wegener's granulomatosis).
No evidence of either acute (e.g., bacterial or viral pneumonia) or chronic (e.g., bronchiectasis) lung infection.
No diabetes, or history of glucose intolerance (e.g., gestational diabetes).
No allergy to methacholine.
No beta-adrenergic blocking medication.
Control subjects must not have a history of asthma, atopic rhinitis or atopic dermatitis.
Control subjects must not have any response to inhaled methacholine with a fall in FEV1 in excess of 20% to less than or equal to 25 mg/ml.
Asthmatic subjects must not have chronic bronchitis or a diagnosis of chronic obstructive lung disease (COPD).