Immunocytochemical demonstration of quantitative differences in the distribution of lysozyme in human airway secretory granule phenotypes

The distribution of lysozyme in the different secretory granules (SG) of human tracheal and bronchial submucosal gland serous cells was studied by light and electron microscopy, using a post-embedding immunogold technique. SG were differentiated into 5 phenotypes according to their structure and staining electron density. All the SG-phenotypes were reactive to lysozyme. In the heterogeneous SG-phenotypes, quantitative immunocytochemistry showed that the density of lysozyme labeling was significantly higher in the electron-dense central core compared to the electron-lucent peripheral rim. At the tracheal level, the density of lysozyme did not vary significantly within the different SG-phenotypes, whereas at the bronchial level, the differences were significant. Moreover, the lysozyme labeling density was much higher in the bronchial than in the tracheal SG.