Immunofluorescent localization of fibronectin in human oral mucosa

Fibronectin in the palatine tonsil as a susceptibility marker in Egyptian rheumatic families: histological and immunohistochemical studies

Rheumatic fever (RF) and rheumatic heart disease (RHD) are the multisystem autoimmune sequel of group A streptococci (GAS) infection of the upper respiratory passages, mainly tonsillopharyngitis. The major receptor on the surface of human palatine tonsil for GAS is fibronectin (FN; adhesin receptor). Early detection of RF susceptibility is considered as an important aim of this study. Therefore, the present study aimed to use FN immunoreactivity (FN-ir) as a marker for early detection of rheumatic susceptible children with palatine tonsil crypts surface epithelium. A total of 30 palatine tonsillar specimens were obtained from children aged from 3 to 15 years. Histological studies showed moderate vascular changes and more than four apparent epithelial disruptions in the crypt epithelium. FN-ir showed a significant increase in FN in the basal layers of surface epithelium, subepithelial connective tissue and interfollicular areas. Tonsils of children in rheumatic families showed significant increase in FN in subepithelial connective tissue areas with more than one apparent crypt epithelial disruption compared to normal children. We can conclude that FN plays a central role in the RF and differentially distributed in the functional compartments of the palatine tonsil in children with RHD, so FN-ir can be used as a marker for rheumatic susceptibility.

Quantitative evaluation of the vasculature and fibronectin localization in gingival connective tissue of smokers and non-smokers

BACKGROUND

It has been shown that tobacco is a significant risk factor for periodontal disease. The reason for decreased gingival bleeding in smokers is not known. The aim of the present study was to demonstrate the localization of fibronectin in the extracellular matrix of the inflamed gingiva of smokers and non-smokers and to evaluate the chronic effect of smoking on the gingival microvessel number (NVES) and vascular surface density (VSD).

METHODS

Seventy-four (74) adult patients with periodontitis were included in this investigation. Of these patients, 38 were smokers and 36 were non-smokers. Probing depths (PD), papillary bleeding index (PBI) of both groups, and the smoking habits of the smokers were recorded. Biopsy specimens obtained during periodontal surgery were prepared to evaluate fibronectin distribution and to quantitate the vasculature.

RESULTS

The mean VSD values of smokers and non-smokers were 6.721 +/- 1.845 and 5.721 +/- 3.118 (mean +/- SD), and the mean NVES of smokers and non-smokers was 31.582 +/- 11.810 and 30.145 +/- 15.442, respectively. The difference between the mean PD and PBI values of the 2 groups was not statistically significant. The location of the biopsy specimen, whether in the anterior or posterior area of the mouth, did not lead to any statistically significant differences between the groups. In addition, the number of years smoked and the tobacco brand used did not result in statistically significant differences. The most intense staining of fibronectin was observed beneath the epithelium around the blood vessels of the uppermost region of the connective tissue, showing a fibrillar and diffuse distribution; however, there was no significant difference between smokers and non-smokers.

CONCLUSION

The results of the present study indicate that smoking does not affect the vascular surface density, number of vessels per mm2 stroma, or fibronectin distribution in subepithelial gingival connective tissue.

Reverse transcription-polymerase chain reaction and immunohistochemical study of the expression of fibronectin mRNA in human submandibular salivary gland

The alternative expression of fibronectin mRNA in submandibular salivary glands was analysed using three groups of polymerase chain reaction probes to amplify the cell-binding domain (CBD), and the extra domain (ED)-A and ED-B exon regions in five normal human adults. The fibronectin CBD region was fairly well expressed in the salivary gland while less than trace amounts of ED-A and ED-B exons were expressed. Immunohistochemical staining with an antihuman plasma fibronectin monoclonal antibody, which recognized specifically the CBD region, demonstrated definite positive cytoplasmic staining in the duct-cell area. On the other hand, an anticellular fibronectin ED-A-specific monoclonal antibody was very low positive in duct cells. The results suggest that salivary fibronectin is synthesized in the submandibular salivary gland only, and does not include the ED-A segment. Furthermore, duct cells also produced fibronectin without ED-A.

Salivary fibronectin in man: an immunoblotting, radioimmunoassay and immunohistochemical study

An antiserum and monoclonal antibody against plasma fibronectin recognized a 230-kDa, intact fibronectin molecule when 1000-fold diluted human plasma was subjected to immunoblot analysis. Immunoblot analysis of the parotid saliva demonstrated that the rabbit antiserum to human plasma fibronectin bound to five molecules (200, 110, 85, 75 and 65 kDa), other than the 230-kDa, intact fibronectin molecule, while the mouse monoclonal antibody recognized only the 230-kDa molecule. The 230-kDa type was not found in whole saliva with either the antiserum or monoclonal antibody. The antiserum reacted with 85-, 75- and 33-kDa molecules, and the monoclonal antibody recognized 75-, 33- and 20-kDa molecules in the whole saliva. Radioimmunoassay revealed that the mean +/- SD of fibronectin concentration in parotid saliva was 2.5 +/- 1.4 ng/ml (n = 20) and 149.8 +/- 46.2 ng/ml (n = 30) for whole saliva. Immunoperoxidase staining with rabbit antiserum and the mouse monoclonal antibody showed positive cytoplasmic staining of cells in the intralobular and interlobular ducts in parotid, submandibular, and sublingual glands. No acinar cells were stained.

Fibronectin is not detectable on the intact buccal epithelial surface of normal rats or humans

Fibronectin (FN) has been postulated to prevent gram-negative bacillary (GNB) colonization of the oropharynx by covering epithelial cell GNB receptors. We investigated the distribution of FN along the luminal surface of oropharyngeal epithelium in animals and humans. Examination of buccal epithelial biopsies obtained from normal rats revealed no luminal surface FN by either immunofluorescent or immunoperoxidase staining. Extraction of epithelial surface proteins and quantitation of FN by rocket immunoelectrophoresis and electrophoretic transfer to nitrocellulose followed by immunologic detection also detected no FN from normal animals' oropharyngeal biopsies. Buccal epithelial biopsies from three normal humans were examined for FN using electrophoretic transfer to nitrocellulose followed by immunologic detection, and no FN was demonstrable. Our results suggest that FN is not present on the oral epithelial surface of healthy rodents or humans, and that FN may not be involved in the pathogenesis of bacillary colonization.

Immunoelectron microscopic study of the basement membrane in oral lichen planus

The present study investigated the nature of basement membrane changes in oral lichen planus. For this purpose antibodies to type IV collagen, laminin and fibronectin were applied in avidin-biotin peroxidase complex staining using a pre-embedding immunoelectron microscopy technique. Immunoreactivity to type IV collagen and laminin was restricted to the sub-basal basement membrane and the basement membrane branches extending into the lamina propria. Immunoreactivity to fibronectin was noted also in the connective tissue as a network-like arrangement of thin strands. Although local activated CDB+ cytotoxic lymphocytes and tissue macrophages may be involved in the local pathogenetic process, these findings suggest that the basement membrane alterations are secondary to pathologic changes in the basal cells.

Localization of fibronectin in gingival connective tissue of the beagle dog. Ultrastructural detection with ferritin and peroxidase-conjugated antibodies

Ferritin and peroxidase-conjugated antibodies were used in an indirect antibody method to localize fibronectin in gingival connective tissues. Fibronectin was found in the basal lamina beneath the epithelium and endothelium. Collagen fibrils associated with the basement membranes were also heavily coated by fibronectin. Amorphous patches of fibronectin were found adjacent to the plasma membrane of epithelial cells as well as free in the interepithelial spaces. Fibronectin was present throughout the connective tissue in close association with individual collagen fibrils, apparently serving as an interfibrillar cementing substance. Patches of fibronectin were located at the cell surface of fibroblasts, plasma cells, lymphocytes, endothelial cells, smooth muscle cells, and neutrophils. These amorphous patches were observed to connect adjacent cells across narrow spaces and to connect cells to collagen fibrils. The heavy labeling for fibronectin visualized by fluorescent microscopy around gingival blood vessels (Cho et al., 1985) can be accounted for by a heavy coating of fibronectin on the collagen fibrils and basal laminas associated with endothelial cells, as well as by the presence of abundant deposits of fibronectin along the cell membranes of endothelial cells and in the intercellular spaces of the vessel wall.

Relationship between fibronectin and lymphoid cells in buccal mucosa, labial salivary glands and palatine tonsil

The distribution of fibronectin in human buccal mucosa and labial salivary glands and its relationship to lymphoid cells was studied using an immunoperoxidase technique and monoclonal and polyclonal antibodies. In all specimens fibronectin was associated with basement membranes of epithelia, vascular endothelium and perineural sheaths. In histologically normal areas of buccal mucosa fibronectin was distributed as a sparse network in the superficial lamina propria. A more extensive network of fibronectin was found within the lamina propria of mucosal specimens infiltrated with T lymphocytes, whereas fibronectin was absent in areas occupied by B lymphocytes. A similar relationship between lymphocyte type and the presence of a fibronectin network was found in labial glands and palatine tonsil. Fibronectin was not detected within oral, salivary gland, tonsillar crypt or capsular epithelium.

Localization of fibronectin in gingival connective tissue of the beagle dog. Immunofluorescent light microscopic findings

Affinity purified antibodies to plasma fibronectin were used to localize fibronectin in the connective tissues of inflamed and noninflamed beagle gingiva. In noninfiltrated gingival connective tissue, fibronectin was demonstrated in the basement membrane beneath gingival epithelium and around blood vessels as a uniform and intensely stained band about 3 to 10 micron thick. Fibronectin was also distributed throughout the connective tissue in association with collagen fibrils as a more diffuse, less intensely stained pattern. The inflamed gingiva included in this study was characterized by proliferation of epithelial pegs, heavy infiltration of plasma cells and loss of collagen within the subepithelial connective tissue. In these sites, fibronectin was present as an intensely stained band around blood vessels and at the crest of connective tissue papillae nearest the sulcular space. The fibronectin in the basement membrane beneath the epithelium appeared diminished and less uniformly distributed. A delicate network of fibronectin was present around plasma cells and the remaining collagen fibers.

Immunologic findings of oral lichen planus

Immunofluorescence (IFL) examination in lichen planus (LP) often reveals fibrin deposition in the basement membrane (BM) zone and colloid bodies (CB) giving a positive IgM fluorescence. Oral biopsies were taken from the involved buccal mucosa of 10 LP patients. IFL examination showed fibrin deposition in the BM area of all patients but in none of the seven controls. CB were found in the upper connective tissue of 5/10 oral and 3/3 skin specimens and they were always positive for fibrin, IgM and keratin. Positive staining with keratin antiserum suggests the epithelial origin of CB but the importance of fibrin and IgM staining remains unknown. Double IFL staining revealed that in areas of heavy fibrin deposition and CB formation the laminin and fibronectin staining was absent, suggesting a damage to BM. Moreover, IFL examinations with serum amyloid P (SAP) antiserum and basic fuchsin (BF) showed alterations indicating that upper connective tissue elastic fiber system is also involved in oral LP.

Alterations in fibronectin distribution in oral mucosal vesiculo-bullous lesions

The distribution of fibronectin in human oral mucosal vesiculo-bullous diseases was studied by indirect immunofluorescence. Subepithelial (benign mucous membrane pemphigoid and erythema multiforme) as well as intraepithelial (pemphigus vulgaris and dyskeratosis follicularis) lesions were selected. A marked accumulation of fibronectin was generally found in the lamina propria and basement membrane region, except in dyskeratosis follicularis. Intraepithelial staining occurred in erythema multiforme and dyskeratosis follicularis. In pemphigus vulgaris intercellular staining was seen in relation to acantholysis. Both mucous membrane pemphigoid and erythema multiforme showed a linear accumulation corresponding to the intact basement membrane. However, only pemphigoid lesions disclosed fibronectin on the epithelial side of the vesicles.

Ultrastructural localization of fibronectin in duct cells of human minor salivary glands and its immunochemical detection in minor salivary gland secretion

Fibronectin (Fn) was localized in duct cells by means of a light and electron microscopic immunohistochemical technique. The subcellular localization demonstrated that Fn is synthesized in these cells and thus not exclusively produced by cells with a mesodermal background. Fn concentration, as measured by radioimmunoassay, was higher in saliva from the minor salivary glands than in unstimulated whole saliva, whereas Fn was undetectable in stimulated parotid saliva. Fn is thus a conspicuous component in unstimulated resting saliva. Fn may be an important factor, negative or positive, for the integrity of the oral hard and soft tissues because it has the capability to bind and agglutinate microorganisms.