Localization of a low molecular weight protease inhibitor to tracheal and mixillary sinus mucosa

Normal human bronchial secretion contains protease inhibitors from plasma and an acid-stable, low molecular weight inhibitor which strongly inactivates granulocyte elastase and chymotrypsin-like cationic proteins. The distribution of this bronchial protease inhibitor in tracheal mucosa was analyzed by an indirect immunoperoxidase method. Strong peroxidase staining was obtained in the columnar ciliated epithelium of the trachea and in the sero-mucus glands. The findings support a local mucosal production of the inhibitor. Maxillary sinus mucosa was also positively stained for the inhibitor.