Protease inhibitors in bronchoalveolar lavage fluid from neonates with special reference to secretory leukocyte protease inhibitor.

An imbalance of proteolytic enzymes and protease inhibitors may contribute to the development of bronchopulmonary dysplasia. We studied secretory leukocyte protease inhibitor (not previously addressed), and alpha 1-antitrypsin, alpha 1-antichymotrypsin, alpha 2-macroglobulin and elastase. Albumin was used as an internal reference. Infants with pneumonia had higher concentrations of secretory leukocyte protease inhibitor (p = 0.02) and elastase (p = 0.04) in bronchoalveolar lavage fluid than those with respiratory distress syndrome; those who also developed bronchopulmonary dysplasia had intermediate values. A decreased concentration of alpha 1-antitrypsin was found in the second and third postnatal weeks (p = 0.002). Further detailed studies of the balance between proteases and protease inhibitors and of the importance of pulmonary infections in the pathogenesis of bronchopulmonary dysplasia are suggested. Secretory leukocyte protease inhibitor is important both as an elastase inhibitor of bronchial mucus and as a marker of infection in the bronchi.