Characterization of epithelial elements in human major salivary glands by functional markers: localization of amylase, lactoferrin, lysozyme, secretory component, and secretory immunoglobulins by paired immunofluorescence staining.

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Abstract
Human parotid and submandibular glands were studied by paired immunofluorescence staining, including a variety of combinations of fluorochrome conjugates with contrasting colors. Lactoferrin (Lf), secretory component (SC), and particularly amylase were demonstrated in serous acinar cells of both glands. In addition, lysozyme (Ly) was present in some acini, although mainly located in intercalated ducts where Lf was also most commonly seen. SC was present in acini, intercalated ducts, and striated ducts but not in large collecting ducts. Staining for SC was generally faint but increased in intensity at the cell periphery and particularly at the luminal face of striated duct cells. Immunoglobulin (Ig) A--and IgM when detectable--showed an epithelial distribution similar to that of SC, in accordance with the known secretory properties of these two Ig classes. Conversely, IgG was not present in epithelial cells, despite its high extravascular concentrations. Mucous epithelial elements did not show unequivocal staining for any of the proteins studied. Formaldehyde fixation, combined with pronase treatment of tissue sections and prolonged exposure (20 hr) to antibody, enhanced markedly the staining intensity for lysozyme; ethanol fixation and 30-min incubation with conjugates generally afforded better localization of the other epithelial components.