Since the seminal description of the technique by Reynolds and Newhall (lA), bronchoalveolar lavage (BAL) has been broadly used to characterize pulmonary inflammation both in the airway and in parenchymal structures. In the last decade, this technique has been increasingly applied to asthma, and to allergic inflammation of the airways. Although not without limitations, both technical and interpretive, studies using the technique of BAL have offered considerable insights into the pathogenesis of asthma. It is now clear that with appropriate precautions, BAL and other invasive airway procedures are quite safe and that well-designed studies can provide useful information not obtainable in other ways. Several statements that provide practical guidance have been published (4-6). Further insights have been developed by using allergen challenges of the airway, delivered either by aerosol or by direct instillation of allergen. Collectively, the use of invasive bronchoscopic techniques has considerably advanced the understanding of asthma and its attendant inflammation (1,2). Most significantly, BAL studies, coupled with those of airway biopsy, brushings, and induced sputum, have provided solid evidence for a characteristic form of airway inflammation associated with asthma. Even in patients with mild or asymptomatic disease airway
inflammation is present and appears to involve many of the same cells observed in fatal disease at autopsy, such as eosinophils, basophils, mast cells, and lymphocytes. These inflammatory cells are part of a complex interaction involving both cells recruited from the circulation to the inflamed airway as well as resident cells in the airway wall. These interactions may ultimately control the degree of airway obstruction and reactivity manifested as the day-to-day variations in airway function of clinical asthma, but they also may underlie the chronic structural changes associated with progressive or fatal disease.