Lectin probes of glycoconjugates in human salivary glands: 1

Antimicrobial defence mechanisms of the human parotid duct

The parotid duct transports saliva from the gland into the oral cavity. However, its immune response properties, along with the secretion and moistening principles of the duct, have not yet been fully investigated. These properties may play an important role in protecting the parotid gland from infection and also prevent development of sialodocholithiasis, as the parotid duct -- in contrast to the submandibular salivary duct -- is often free of duct concrements. Up to now, only the parotid gland has been investigated, without regard to its duct. The present study analyses the structures of the parotid duct in their relations to antimicrobial defence mechanisms and rheological properties. Investigations were performed on 23 parotid ducts using histological, histochemical and immunohistochemical methods. Epithelial and goblet cells of the parotid duct synthesize a complex mucous layer that covers the epithelium. The viscosity is influenced by secreted mucins and TFF peptides. This layer contains carbohydrates including N-acetyl-glucosamine, N-acetyl-galactosamine, galactose, mannose, fucose and sialic acids. The lamina propria contains granulocytes, T lymphocytes and macrophages. IgA, produced by plasma cells in the subepithelial layer, is frequently integrated in the secretory product. Synthesized mucins, TFF peptides, carbohydrates and immunoglobulins form a complex layer that can be expected to prohibit infection and enables salivary flow. Our study demonstrates that the steady secretion of the parotid gland, together with the ductal cellular and biochemical immune protection system, is likely to thwart ascending infections in the parotid duct and gland.

Expression of glycoconjugates in normal and Sjögren's syndrome labial glands

Glyconjugate expression in formalin-fixed, paraffin-embedded Sjögren's syndrome labial glands (nine cases) was compared with that in normal glands (12 samples) using a wide panel of lectins. Mucous cells expressed mainly mucous-type glycoproteins including sialyl, fucosyl, galactosyl and galactosaminosyl residues, and some N-linked glycoconjugates. Demilunar cells expressed mainly alpha D-mannose, GlcNAc and Gal beta 1.3-GalNAc. Duct cells and cellular glycocalyx expressed O-linked and N-linked residues. Sjögren's syndrome samples showed a statistically significant increase in the expression of GlcNAc. A significantly decreased expression of Gal beta 1,3-GalNAc and alpha D-mannose, residues not usually present in mucous cells, was found (p < 0.05). This suggests that anatomic rather than functional alterations determine mucous cell impairment and the symptoms in Sjögren's syndrome.

Lectin histochemistry of glycoconjugates in horse salivary glands

The glycoconjugate content of major horse salivary glands was investigated by means of horseradish peroxidase-conjugated lectins. Qualitative differences were observed in the terminal sugar residues of secretory glycoproteins and glycoconjugates linked to the apical surface of excretory duct epithelial cells. Mucous acinar cells in mandibular and sublingual glands contained oligosaccharides with D-galactose, alpha- and beta-N-acetylgalactosamine, N-acetylglucosamine and fucose residues, whereas mandibular, sublingual and parotid serous cells contained only oligosaccharides with terminal alpha- and beta-N-acetylgalactosamine residues. The apical portion of striated and interlobular duct lining cells of mandibular and sublingual glands stained for alpha- and beta-N-acetylgalactosamine and for N-acetylglucosamine. In parotid gland the cytoplasm of intercalated duct cells and the apical surface of striated duct epithelial cells stained for alpha-N-acetylgalactosamine.

Immunochemistry of high molecular-weight human salivary mucin

The purpose of this study was to determine the distribution of mucin glycoprotein 1 (MG1) within submandibular, parotid, labial and palatine salivary tissues. Formalin-fixed and frozen tissue sections were examined histochemically with PAS, Alcian blue and Meyer's mucicarmine, and immunocytochemically with an anti-mucin glycoprotein 1 monoclonal antibody (clone 3/E8). Clone 3/E8 was produced in Balb/c mice using mucin-enriched chromatographic fractions from submandibular-sublingual saliva. The monospecificity of 3/E8 was confirmed by immuno-dot blotting and SDS-PAGE/electrophoretic transfer. Clone 3/E8 (IgG1; kappa) was of moderate affinity, and was directed to a carbohydrate-containing, TPCK-trypsin-insensitive and pronase-insensitive epitope on this mucin, which was not blood-group specific. The location of mucin glycoprotein 1 was determined by both indirect (peroxidase-antiperoxidase) and direct methods. Mucin glycoprotein 1 was localized within all labial acini examined, but was not found within parotid tissues. Histochemical methods stained all submandibular, palatine and labial acini, but immunocytochemistry with monoclonal antibody revealed heterogeneous staining with clone 3/E8 in submandibular and palatine tissues. These findings suggest the presence of mucin glycoprotein 1-specific acinar cell subpopulations within human submandibular and palatine salivary tissues.

Human salivary gland glycoconjugates: a lectin histochemical study

The glycoconjugate content of normal salivary glands has been extensively investigated in humans by biochemical means and in non-human mammals by histochemical methods. However, there have been few histochemical studies of human tissues. This paper describes the findings obtained in parotid, submandibular and minor salivary glands by applying a panel of 13 biotinylated lectins, directed against a range of N-linked, fucosylated and galactosylated sequences, using an avidin-peroxidase technique, with appropriate enzymatic and inhibitory sugar controls. The results were generally in accord with those observed in biochemical assays but the use of lectin histochemistry permitted the localization in situ of small amounts of oligosaccharide and, therefore, allowed the recognition of subtle tissue differences. This study expands the current knowledge on the glycoconjugate composition of salivary glands and their lectin histochemistry and serves as a baseline for further studies, particularly in the field of neoplasia.

Conjunctival cell glycoprotein pattern of healthy persons and of patients with primary Sjögren's syndrome--light microscopical investigation using lectin probes

Formalin-fixed biopsies of conjunctival tissue from the lower fornix of 10 healthy persons and of 10 patients with primary Sjögren's syndrome (primary SS) were examined by light microscopy. Deparaffinized, rehydrated sections of 5 microns were incubated overnight, each with one of 15 different biotinylated lectins. Bound lectins were visualized using avidin-HRP-substrate complexes. Five lectins did not bind to conjunctival cells, and further six lectins bound in an unspecific manner to conjunctival cells of both healthy persons and of primary SS patients. Jacalin lectin bound selectively to goblet cells of all specimens. Peanut agglutinin (PNA) and wheat germ agglutinin (WGA) bound significantly stronger to basal conjunctival epithelial cells of patients with primary SS. This binding pattern may be of diagnostic value.

Immunohistochemical and fluorescent microscopic study of histogenesis of salivary mucoepidermoid carcinoma

The purpose of the present investigation was to study the histogenesis of the mucoepidermoid carcinoma of the salivary glands. Eleven cases of mucoepidermoid carcinoma of the minor salivary glands and five of the major glands were extensively studied employing immunohistochemical and fluorescent microscopic techniques. Both the intermediate cells and the duct cells showed a rather similar pattern of reactivity for vimentin, actin and EMA. Also, the intermediate cells and the myoepithelial cells showed a similar reaction pattern for keratin and UGA-1. The intermediate, myoepithelial and duct cells shared a similar reaction pattern for desmin, myosin, CEA, and S-100 protein. However, the rest of the tumor markers studied (AFP, PNA and WGA) were found to be non contributary. We also found that the intermediate and to some extent the epidermoid tumor cells showed a positive reaction with Azophloxine GA, which is a selective stain for myoepithelial cells in the normal glands. Based on these findings, the duct cells, the myoepithelial cell in the normal glands and the intermediate cells of the mucoepidermoid carcinoma share certain similar characteristics. The intermediate cells may actually be a mixed population, some having characteristics of the myopithelial cells and others of duct cells. These findings are relevant to the possible role of the intermediate cell in the histogenesis of the mucoepidermoid carcinoma.

Lectin histochemistry of ameloblastomas and odontogenic keratocysts

The cell membrane carbohydrate components of 10 simple (follicular and/or plexiform pattern) and 5 acanthomatous ameloblastomas, one plexiform unicystic ameloblastoma, one soft tissue ameloblastoma and 11 odontogenic keratocysts were studied in paraffin-embedded tissues using horseradish peroxidase-conjugated lectins. The presence of glucose and mannose was demonstrated by intense labelling with Concanavalin ensiforme (Con A) in 73% of the ameloblastomas examined, while periodate oxidation of the specimens prior to Con A (PA/Con A) stained 53% of the cases. Ameloblastomas did not express receptors for Triticum vulgaris (WGA), Erythrina chrystagalli (ECA), Arachis hypogea (PNA), and Ulex europaeus (UEA-1). The plexiform unicystic ameloblastoma and the soft tissue ameloblastoma examined showed the same cell membrane glycoproteins as the simple and acanthomatous ameloblastomas. Forty-five per cent of the keratocysts demonstrated Con A reactivity from the basal to the keratinized layer, while 72% of these specimens showed positive PA/Con A reactivity from the parabasal to the keratinized layer. Staining with WGA, ECA, PNA, and UEA lectins also revealed the presence of N-Acetyl-glucosamine and fucose oligosaccharides in the plasma membrane of basal, spinous and keratinized cell layers of the odontogenic keratocysts. The distinct cell surface carbohydrate composition of the ameloblastoma and odontogenic keratocyst may be responsible for the differences in biological behavior in these conditions.

Heterotopic gastrointestinal cyst of oral cavity: a developmental lesion?

A case of a rare heterotopic gastrointestinal cyst of the oral cavity is presented together with evidence from mucin histochemistry studies that supports a developmental origin for these lesions.

Lectin probes of glycoconjugates in human salivary gland neoplasms: 2

Lectins are proteins or glycoproteins which exhibit a high affinity for specific sugar molecules. Terminal sugars on cell surface or cytoplasmic oligosaccharides bound to proteins and lipids can be probed with lectins. This study records the lectin-binding characteristics of 20 salivary gland neoplasms and compares them with observations in normal human serous and mucous salivary glands. The results of this study support the current histogenetic concepts for the development of some of the salivary gland neoplasms.