Asthma: application of cell and molecular biology techniques to unravel causes and pathophysiological mechanisms

The condition termed "asthma" has been difficult to define satisfactorily. Much of this problem arises from poor understanding of its causes, natural history, and pathophysiology, and also from a lack of a specific marker(s) of the disease. To the clinician, the diagnosis of asthma is not difficult in most cases, particularly if patients present early with symptoms of intermittent wheeze and chest tightness, and if their symptoms respond to particular treatments, such as β-adrenergic agonists. Early definitions of asthma included the presence of airway obstruction that could spontaneously reverse with treatment, and also the increased narrowing of the airways to non-specific bronchoconstrictor stimuli, i.e., bronchial hyperresponsiveness (BHR). The essential elements of this definition were useful in separating asthma from other conditions, such as chronic bronchitis, chronic obstructive pulmonary disease, and emphysema, which could sometimes be diagnostically confused with asthma. More recently, the definition of asthma has been enhanced by the recognition that the airway submucosa of patients with asthma are chronically inflamed with a typical inflammatory infiltrate, and that inflammatory processes are important causes of the chief characteristics of asthma: airway obstruction and BHR. In addition, the loss of reversibility of airway obstruction as a long-term effect of the chronic inflammatory process is recognized: