Ultrastructural localisation of lactoferrin and glycoprotein in human bronchial glands.

The distribution of lactoferrin and glycoprotein in human bronchial glands has been studied by electron microscopy using an immunoperoxidase method to stain the former and a periodic acid-chromic acid-silver methenamine sequence for the latter, each applied to ultrathin Epon sections. The distribution of lactoferrin corresponds to that of lysozyme. Lactoferrin and lysozyme are both confined to serous acini where the granules show a variable pattern of staining. Some serous granules are filled uniformly with lactoferrin, some lack lactoferrin in a small central core or a thin peripheral rim, and some are completely devoid of lactoferrin. Glycoprotein is present in all mucous granules but only certain serous granules. The latter may be filled uniformly with glycoprotein or glycoprotein may form a thin peripheral coat about centrally located lactoferrin and lysozyme. An electron-dense central core found in some serous granules contains neither glycoprotein, lactoferrin, nor lysozyme.