Abstract

Tissue kallikrein is the major kininogenase detected in bronchoalveolar lavage fluids from asthmatics and may play a particularly important role in kinin generation during asthma. The present study was undertaken to determine the source of tissue kallikrein in the human lower airways. Specific antisera to human tissue kallikrein were used to localize this enzyme by immunocytochemistry in human trachea. Immunoreactive tissue kallikrein was localized in submucosal glands of the lamina propria but was not detected in epithelial cells or goblet cells. Specific staining for tissue kallikrein was not detected in all cells of the submucosal glands but was restricted to cells forming demilunes in the distal portions of the glands. When consecutive serial sections of submucosal glands were alternately stained using antiserum to tissue kallikrein and a periodic acid Schiff stain (to detect mucus), it was revealed that immunoreactive tissue kallikrein was present only in serous cells and not in mucus cells. The localization of tissue kallikrein to the serous cells of submucosal glands should facilitate studies to regulate the release of this enzyme. Regulation of tissue kallikrein release may provide a mechanism to reduce kinin generation during asthma.