Asthma

Asthma is a complex syndrome with many clinical phenotypes in both adults and children. Its major characteristics include a variable degree of airflow obstruction, bronchial hyperresponsiveness, and airway inflammation. For many patients, the disease has its roots in infancy, and both genetic factors (atopy)1,2 and environmental factors (viruses,3 allergens,4 and occupational exposures5) contribute to its inception and evolution. To comprehend the pathogenetic mechanisms underlying the many variants of asthma, it is essential to identify factors that initiate, intensify, and modulate the inflammatory response of the airway and to determine how these immunologic and biologic processes produce the characteristic . . .