Local immune system in human adult and fetal larynx.

Using immunofluorescent and histopathologic techniques, we studied the distribution and secretory activity of the glands of the larynx from 51 adults and 15 human fetuses. Glandular buds were first observed at the 12th fetal week and glandular distribution became evident from the 16th fetal week. In the adult larynx, intraepithelial and submucosal glandular distribution was observed in each specimen. Immunofluorescent studies revealed the diffuse fluorescence for IgA not only in the submucosal or periglandular connective tissue are but also in the intraepithelial and submucosal glands. Secretory component (SC) synthesis was found mainly in each serous-type glandular epithelium or acinus. In the submucosal or periglandular area, IgA-producing plasma cells were numerous. In contrast, there was little fluorescence for IgA in the fetal laryngeal tissues. Secretory component, however, was found in each serous-type glandular epithelium or acinus from the 16th week. Our observations suggest that local immune system by secretory IgA is active in the adult larynx, and the production of SC is inherently acquired in the fetal larynx.