Local immune system in the developing fetal larynx.

Using histopathological and immunofluorescent techniques, we investigated the development of the glandular system of the larynx from 12 human fetuses. Glandular buds were first observed at the fourth month of gestation and glandular distribution became evident from the fifth month in the larynx. Ciliated or nonciliated epithelium covered the cavity of the larynx, with the exception of the true vocal cord. Immunofluorescent examination revealed the presence of IgG in the fetal larynx, but there was little fluorescence for IgA, IgM and IgE. Secretory component (SC) synthesis, on the other hand, was found in each serous-type glandular epithelium or acinus from the fourth month on. Our observations suggest that the local immune system by SC, which binds to IgA as SIgA in human laryngeal mucosa, is inherently acquired in the fetal larynx.