Use of Bronchoalveolar Lavage in Humans—Past Necessity and Future Imperative

Limited bronchoalveolar lavage (BAL) as an extension of fiberoptic bronchoscopy has permitted the recovery of airway-alveolar space cells and soluble substances in the extracellular lining fluid that have been used diagnostically and as research specimens in patients with a variety of lung diseases and in normal subjects for the study of lung host defenses. During the past three decades, use of BAL specimens has stimulated immunologic and cellular research of pulmonary diseases, which has provided significant insight into local host immunity, inflammation, fibrogenesis, asthma mechanisms, and infections. From this research new methods of antifibrotic therapy of interstitial pulmonary fibrosis, for example, have followed. Moreover, BAL applications have greatly enhanced professional interest in the field of pulmonary medicine. This review attempts to analyze the history and impact of BAL, appraise its current status, and assess its future usefulness. Understanding the immunopathogenesis of many lung diseases is predicated on obtaining in situ specimens from affected lung tissue and airways. BAL provides a direct sample that can be compared with an endobronchial or transbronchial biopsy tissue specimen and with cellular and immunologic components in the vascular circulation. Thus, the recovery of BAL fluid and its components involved directly with a disease process or continguous with interstitial tissue permits a much more detailed assessment of new cellular mediators and cytokines participating in the pathologic process. Furthermore, subjecting BAL cells to microarrays of DNA to discern what genes are activated will be one step closer to identifying intracellular processes involved or deranged. Identification of causative factors may solve questions of causation, so that preventive strategies or definitive therapy can be used.