Small Airways Disease in Asymptomatic and Symptomatic Subjects With Airway Hyperresponsiveness (AHR)

Inclusion criteria for asymptomatic subjects with airway hyperresponsiveness (AHR) : * Age between 18 and 65 years. * Forced expiratory volume in one second (FEV1) \> 80% predicted post bronchodilator. * Provocative concentration causing a 205 fall in FEV1 (PC20) methacholine \<8 mg/ml. * No history of asthma or previous use of asthma medication. Inclusion criteria for asymptomatic subjects without AHR : * Age between 18 and 65 years. * FEV1 \> 80% predicted post bronchodilator. * PC20 methacholine \>8 mg/ml. * No history of asthma or previous use of asthma medication. Inclusion criteria for patients with asthma: * Age between 18 and 65 years. * FEV1 \> 80% predicted. * PC20 methacholine ≤8 mg/ml. * Doctor's diagnosis of asthma. * No history of Chronic obstructive pulmonary disease (COPD). Exclusion Criteria: * Use of inhaled or oral steroids, antihistamines, nedocromil, theophylline, leukotrien antagonists or long-acting beta-agonists for at least three weeks before the start of the study. * Any disease that may affect the outcome of the study as judged by the Investigator. * FEV1 \<1.2 liter.