Phenotypic characterization of resident macrophages in submandibular salivary glands of normal and isoproterenol-treated rats

Nonproliferative and Proliferative Lesions of the Gastrointestinal Tract, Pancreas and Salivary Glands of the Rat and Mouse

The INHAND (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions in Rats and Mice) project is a joint initiative of the Societies of Toxicologic Pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP), and North America (STP) to develop an internationally accepted nomenclature and diagnostic criteria for nonproliferative and proliferative lesions in laboratory animals. The purpose of this publication is to provide a standardized nomenclature and diagnostic criteria for classifying lesions in the digestive system including the salivary glands and the exocrine pancreas of laboratory rats and mice. Most lesions are illustrated by color photomicrographs. The standardized nomenclature, the diagnostic criteria, and the photomicrographs are also available electronically on the Internet (http://www.goreni.org/). Sources of material included histopathology databases from government, academia, and industrial laboratories throughout the world. Content includes spontaneous and age related lesions as well as lesions induced by exposure to test items. Relevant infectious and parasitic lesions are included as well. A widely accepted and utilized international harmonization of nomenclature and diagnostic criteria for the digestive system will decrease misunderstandings among regulatory and scientific research organizations in different countries and provide a common language to increase and enrich international exchanges of information among toxicologists and pathologists.

A perspective of comparative salivary and breast pathology. Part I: microstructural aspects, adaptations and cellular events

This is the first part of a review comparing the pathology of salivary and mammary glands. Here, less obvious similarities and differences in functional histology and their influences on pathology are examined with emphasis on myoepithelial cells, stromal components, analogues of mucosa-associated lymphoid tissue, steroid receptors, and intraparenchymal cells of monocytic lineage. Particular cell phenotypes (oncocytic, apocrine, neuroendocrine and clear) are critically evaluated and responses to atrophy, infarction and fine-needle aspiration biopsy procedures are highlighted together with aspects of metaplasia, regeneration, ageing and microcalcification. Areas of controversy or uncertainty which may benefit from further investigations are also discussed.

Phenotypic characterization of mononuclear inflammatory cells following equine hydroxyapatite/collagen block grafting in rats

To measure the inflammatory changes associated with the implantation of an equine hydroxyapatite and collagen-containing block graft (eHAC block) in a rodent model system, an eHAC block graft was implanted subcutaneously in rats. Control groups included saline, turpentine oil, and human mineralized particulate allograft (hMPA). Animals were sacrificed and tissue samples obtained after three days, as well as after 1, 2, 4 and 8 weeks. A panel of immunologic probes was used to identify circulatory monocytic cells (ED1), resident mononuclear phagocytes (ED2), mononuclear phagocytes of lymphoid origin (ED3), expression of Ia antigen (OX6), T-cells (OX19), and B-cells (OX33). Immunocytochemical localization was performed and mononuclear cells localized with each immunologic probe counted. Rat sera obtained after eight weeks were used for nitrocellulose dot-blotting to assess circulating anti-equine immunoglobulins. Statistical analysis was performed using two-way analysis of variance, in conjunction with the Bonferroni correction to account for multiple comparisons. A transient increase in monocytes at 3 days and 1 week was observed in all groups, but was significantly higher in the turpentine control (P < 0.0001). A significant increase in the numbers of mononuclear cells detected with clones ED2 and ED3 was observed in specimens from the turpentine group, in contrast to the other groups in the 3 day to 4 week interval (P < 0.0001), as well as within all time periods (P < 0.0001). A statistically significant difference in numbers of ED3-positive cells was observed in the hMPA group compared to the saline and the eHAC block groups after one week (P < 0.0001). Significantly more OX6-positive cells were observed in the turpentine group, compared to other groups (3 days to 1 week; P < 0.0001). T-lymphocytes were essentially absent except for rats given turpentine (after 1 week). No B-lymphocyte response was found and none of the rats developed systemic anti-equine antibodies. These data indicate that a cellular immune response is not elicited following implantation with the eHAC block graft, which might serve as an alternative material for regenerative therapy.

Distribution of dendritic cells in normal human salivary glands

Dendritic cells (DC) are believed to contribute to development of autoimmune sialadenitis, but little is known about their distribution in normal salivary glands. In this study, DC were identified and their distribution was determined in normal human parotid and submandibular glands. For light microscopy, salivary gland sections were stained with H&E or immunocytochemically using antibodies to DC markers. Transmission electron microscopy (TEM) was used to evaluate the ultrastructural characteristics of DC. In H&E sections, elongated, irregularly shaped nuclei were occasionally seen in the striated and excretory duct epithelium. Immunolabeling with anti-HLA-DR, anti-CD11c and anti-S100 revealed DC with numerous processes extending between ductal epithelial cells, often close to the lumen. Morphometric analyses indicated that HLA-DR-positive DC occupied approximately 4–11% of the duct wall volume. Similar reactive cells were present in acini, intercalated ducts and interstitial tissues. TEM observations revealed cells with indented nuclei containing dense chromatin, pale cytoplasm with few organelles, and lacking junctional attachments to adjacent cells. These results indicate that DC are abundant constituents of normal human salivary glands. Their location within ductal and acinar epithelium suggests a role in responding to foreign antigens and/or maintaining immunological tolerance to salivary proteins.

Organic secretory products, adaptive responses and innervation in the parotid gland of ferret: A histochemical study

To qualify cellular events of possible pathophysiological significance in the parotid of ferret, tissue obtained post-mortem from mature animals of either sex was examined by light microscopical histochemistry for calcium, protein, amino acids, mucosubstances and hydrolases, and by neurohistology. Calcium was localised in acinar cells replete with granules containing protein, disulphides and usually carboxylated mucosubstances. Acid phosphatase activity was basally concentrated in the acinar cells. The granular luminal region of striated ductal cells showed protein, tryptophan, disulphides, neutral mucosubstances, and E600-sensitive esterase and Naphthol AS-D chloroacetate esterase activities, whereas their basal region showed acid phosphatase activity. Strong periluminal activity of acid phosphatase and E600-resistant esterase characterised the collecting ducts. Cholinesterase activity was associated with an extensive network of nerve fibres embracing parenchyma. Catecholamine fluorescence was not seen. beta-glucuronidase reactive macrophages abounded in the interstices. The results suggest that while the acini in the parotid of ferret secrete polyionic glycoproteins, shielded by calcium, the striated ducts secrete tryptophan-rich products comprising neutral glycoproteins and showing proteolytic activity. Innervation is of the cholinergic type and parenchymal lysosomal activity, possibly related to autophagy of stored secretory products and heterophagy of luminal material, is brisk. Macrophages contribute to maintaining the glandular microenvironment, wherein secretory activity appears to be lethargic.

Cellular inflammatory response to porcine collagen membranes

OBJECTIVES

The purpose of this study was to assess local inflammatory changes associated with the implantation of three different porcine collagen membranes having potential use in periodontal regeneration.

METHODS

Materials were implanted subcutaneously into prepared sites along the dorsal skin surface of 60 female Wistar rats. Saline and turpentine were used as negative and positive controls, respectively. Animals were killed and biopsies obtained after 3 d, and at 1, 2, 4, 6, and 8 weeks after membrane implantation. A panel of six monoclonal antibodies was used to identify circulating monocytes (ED1), resident tissue macrophages (ED2), lymphoid macrophages (ED3), Ia-antigen expression (OX6), T-lymphocytes (OX19), and B-lymphocytes (OX33). Cells identified by each antibody were subjected to quantitative immunocytochemistry to compare any differences present among groups. Sera obtained 8 weeks after grafting were used in immunoblotting assays to detect the presence of systemic antiporcine antibodies.

RESULTS

We found that the mononuclear cell subsets associated with implantation of porcine collagen membranes were similar to those obtained with saline administration. On the other hand, the use of turpentine resulted in an inflammatory infiltrate characterized by significantly higher numbers of all six monoclonal cell subsets at all time periods evaluated, compared to either saline or any of the membranes (P < 0.001).

CONCLUSIONS

The collagen membranes do not appear to be associated with a significant local inflammatory response, nor a systemic immune response, and thus appear to be well tolerated, rendering them useful in periodontal regeneration.

Immunohistochemical identification of antigen presenting cells in rat salivary glands

Mucosal dendritic cells affect immune responses through secretion of cytokines and exposure of naïve B- and T-lymphocytes to foreign matter as antigen presenting cells (APCs). APC in oral tissues may play a role in the development of local and secretory immune responses [Crit. Rev. Oral Biol. Med. 7 (1996) 36]. Previous studies have shown that APC are present in the interstitial tissues of rat salivary glands [Arch. Oral Biol. 40 (1995) 1015]. This study sought to further define the distribution of APC in salivary glands. The major glands and ducts of male Sprague-Dawley and Wistar rats were fixed with 4% paraformaldehyde and prepared for immunofluorescence and pre- and post-embedding immunoelectron microscopy. Monoclonal antibodies to the dendritic cell marker Ia antigen (OX-6 antibody), monocyte lineage cytoplasmic antigen (ED-1), and resident tissue macrophage antigen (ED-2) were visualized with FITC-conjugated secondary antibodies for light microscopy and HRP- and gold-labelled secondary antibodies for electron microscopy. Light microscopy revealed numerous OX-6-positive cells with branching processes in the epithelium of striated and excretory ducts of both rat strains, as well as in the connective tissue stroma. ED-1-positive cells had a similar distribution but exhibited a more compact shape with fewer processes. ED-2-positive cells were found only in the connective tissue. Acinar and duct epithelial cells were unreactive. Electron microscopy confirmed that both OX-6-positive and ED-1-positive, non-epithelial cells were present within the duct epithelium. The presence of APC in the duct epithelium suggests that these ducts may be exposed to antigens, possibly by retrograde access from the oral cavity, and that APC located in the salivary gland epithelium may participate in local immune responses.

Effects of melatonin on macrophages/microglia in postnatal rat brain

The present study examined the response of macrophages/microglia to multiple injections of melatonin in the pineal gland and different regions of the brain. The macrophages/microglia showed a significant increase in cell numbers and upregulation of complement type 3 receptors (CR3), major histocompatibility complex class I (MHC I) and class II (MHC II) antigens, and antigens of monocyte/macrophage lineage, as detected by the antibodies OX-42, OX-18, OX-6, and ED1, respectively. The upregulation of the above antigens was observed in 1-d-old rats given daily injections of melatonin and killed at 7-11 d of age; no noticeable change was observed at earlier time intervals. The macrophages/microglia expressing the above antigens appeared round and showed a vacuolated cytoplasm compared with ramified cells in the control rats. Upregulation of CD4 antigens as detected with the antibody W3/25 was also observed in macrophages/microglia in the corpus callosum and epiplexus cells in the lateral ventricles, but not in the pineal gland and the cerebral cortex in the same age group. In rats killed between 2 and 5 d, and at 14 d of age after melatonin treatment, the immunoreactivities of macrophages/microglia with the above mentioned antibodies were comparable to cells in the control rats. Immunoreactive cells were not detected in any of the age groups in melatonin-treated or control rats with the antibodies W3/13 and OX-33, which are markers for T and B lymphocytes. It is concluded that CR3 receptors, MHC antigens, and CD4 antigens on macrophages/microglia are upregulated following melatonin administration. On the other hand, once the melatonin treatment is discontinued the expression of the various antigens/receptors returns to normal levels, suggesting that increased immune potentiality and its maintenance in these cells require the continuous action of the drug.

Phenotypic characterization of mononuclear inflammatory cells in salivary glands of bio-breeding rats

The purpose of this study was to assess whether mononuclear cell abnormalities exist in salivary glands from autoimmune Bio-Breeding (BB) rats. Frozen sections of gland tissues were prepared from five diabetes-resistant BB rats (BB-DR), from five BB rats with diabetes (BB-DP) and from five Wistar rats. A panel of six monoclonal antibodies was used to identify membrane antigens associated primarily with monocytes (ED1), mature tissue macrophages (ED2), lymphoid macrophages (ED3), MHC class II (Ia) antigen (OX6), CD5+ T lymphocytes (OX19), and rat B lymphocytes (OX33). Normal submandibular, sublingual and parotid glands contained few ED1-positive cells, usually two or fewer per field. Tissue macrophages identified by clone ED2 comprised a major mononuclear cell subset in both Wistar and BB rats. However, the number of ED2-positive mononuclear cells was significantly depressed in the submandibular and parotid glands from BB-DR and BB-DP animals, being present in quantities 25-50% of those observed in glands from normal Wistar rats (p < 0.001). In contrast, 25- to 30-fold greater numbers of ED3-positive macrophages were observed in submandibular glands from BB rats (p < 0.001). MHC class II (Ia) antigen expression also was 4- to 6-fold greater in BB rat submandibular glands, compared to Wistar rats (p < 0.001). CD5+ T-lymphocytes were rare or entirely absent in BB sublingual glands (0 to 1 cell per 0.87 mm2 field), compared to 47 cells per field from Wistar sublingual glands. No B lymphocytes were identified with antibody OX33 in any of the rat strains. These findings indicate that BB rat salivary glands differ significantly from Wistar salivary glands. In BB rats there is a rich population of ED3-positive macrophages and T lymphocytes in submandibular gland, low quantities of T lymphocytes in sublingual gland, and fewer ED2-positive macrophages in all three major salivary glands. These differences in mononuclear cell subpopulations may also influence salivary gland function in mucosal immunity.

Cellular inflammatory responses to implanted dental materials

Cellular inflammatory responses to subcutaneous implantation of amalgam and composite resins were assessed in rats by use of histologic and immunocytochemical methods 2 days to 8 weeks after implantation. Frozen and paraffin sections were obtained from subcutaneous tissues associated with amalgam and composite resin suspensions. The amalgam induced mild inflammation with proliferation of few resident macrophages, but implantation of composite resins was associated with an influx of monocytes, increased numbers of resident connective tissue macrophages, and abnormal major histocompatibility antigen class II (Ia antigen) expression. The data suggest that composite resins may produce a a more pronounced inflammatory response than dental amalgams do when incorporated in soft tissues.

Mononuclear cells in salivary glands of normal and isoproterenol-treated rats

The purpose of this study was to analyse the phenotypical distribution of resident cells of the mononuclear phagocyte system in rat salivary glands, and to determine whether isoproterenol induces alterations in macrophage and lymphocyte surface-marker expression. Frozen sections of gland tissues were prepared from five normal rats, and from six rats treated with 20 mg/kg isoproterenol/day for 10 days. A panel of six monoclonal antibodies was used to identify membrane markers associated primarily with monocytes (ED1), mature tissue macrophages (ED2), lymphoid macrophages (ED3), MHC class II (Ia) antigens (OX6), CD5-positive T lymphocytes (OX19), and rat B lymphocytes (OX33). Double-labelling techniques were used to detect the coexpression of ED1/ED2 and OX6/ED2 mononuclear cell markers in the major salivary glands. ED2-positive macrophages were predominant in all three major glands, ranging from 96 cells/0.87 mm2 field in the parotid gland to 165 cells/0.87 mm2 in the submandibular. OX19-positive T lymphocytes were rarely observed in submandibular and parotid glands but represented a distinguishing feature of the sublingual. Moderate numbers of ED3-positive macrophages also were detected in sublingual tissues. In the submandibular and parotid glands, isoproterenol resulted in a decrease in ED2-positive cells, but ED2-positive macrophages increased in sublingual glands with isoproterenol. Isoproterenol resulted in a decrease in MHC class II antigen expression on submandibular and sublingual mononuclear cells but an induction of Ia antigen in the parotid gland. Double labelling revealed that isoproterenol induced coexpression of ED1/ED2 markers on mononuclear cells in the submandibular glands, but ED1/ED2-positive cells were absent from other glands. However, coexpression of MHC class II markers on ED2-positive cells in the sublingual and parotid glands of normal rats was frequently observed, with isoproterenol decreasing coexpression in the sublingual gland and increasing it in the parotid. B lymphocytes were not detected in any of the glands examined. These findings indicate that important differences exist in normal resident mononuclear cell subsets among the major salivary glands of the rat. The differential effects of isoproterenol on inflammatory cells may reflect important differences in local salivary gland immunoregulation. Although salivary gland inflammation induced by isoproterenol does not appear to result from immune mechanisms, the rich population of T lymphocytes and ED3-positive macrophages, and presence of MHC class II antigens, suggest that the sublingual gland may function as an immune organ and have a role in mucosal immunity.

Phenotypic characterization of mononuclear cells following anorganic bovine bone implantation in rats

The purpose of this study was to measure inflammatory changes associated with implantation of anorganic bovine bone and bovine bone/collagen composite grafts, and to compare the response to that obtained following grafting with hydroxyapatite. Anorganic bovine bone, either with or without bovine collagen, as well as granular and block forms of synthetic hydroxyapatite, were implanted subcutaneously in Wistar rats. Saline and turpentine oil were used as controls. Biopsies were obtained after 3 days and at 1, 2, 4, 6, and 8 weeks. A panel of 6 monoclonal antibodies was used to detect monocytes, several distinct macrophage subsets, Ia-antigen expression, and T- and B-lymphocytes. Cells identified by each antibody were counted after immunocytochemical staining, and sera obtained 6 weeks after grafting were used in immunoblotting assays to detect antibodies to bovine serum proteins and collagen. Anorganic bovine bone, bovine bone/collagen, and hydroxyapatite all produced a transient macrophage infiltrate that was maximum 3 days after implantation, but resolved to normal levels within 6 to 8 weeks. Lymphocyte infiltration was not elicited by any bovine graft material, and antibodies to bovine serum proteins or type I collagen were not detected in any of the animals examined. These data indicate that a systemic or local immune response does not develop following implantation with anorganic bovine bone or with anorganic bovine bone/collagen materials. It appears appropriate to explore further the merits of these materials for periodontal regenerative procedures.