Interepithelial cells of the oral mucosa. Light and electron microscopic observations in germfree, specific pathogen-free and conventionalized mice

Adhesion of anaerobic periodontal pathogens to extracellular matrix proteins

Extracellular matrix (ECM) proteins are highly abundant in the human body and can be found in various tissues, most prominently in connective tissue and basement membrane. For invasive bacterial pathogens, these structures function as physical barriers that block access to underlying tissues. The ability to bind and degrade these barriers is important for the establishment of infections and migration to other body sites. In the oral cavity, the ECM and the basement membrane (BM) are important components of the Junctional epithelium (JE) that closes the gap between the teeth surface and the mucosa. In periodontitis, the JE is breached by invading pathogenic bacteria, particularly strict anaerobic species. In periodontitis, invading microorganisms induce an unregulated and destructive host response through polymicrobial synergism and dysbiosis that attracts immune cells and contributes to the destruction of connective tissue and bone in the periodontal pocket. Colonization of the periodontal pocket is the first step to establish this infection, and binding to ECM is a major advantage in this site. Several species of strict anaerobic bacteria are implicated in acute and chronic periodontitis, and although binding to ECM proteins was studied in these species, few adhesins were identified so far, and the mechanisms involved in adhesion are largely unidentified. This review summarizes the data available on the interaction of strict anaerobic bacteria and components of the ECM.

Langerhans cells and their role in oral mucosal diseases

Dendritic cells are arguably the most potent antigen-presenting cells and may be the only cells capable of initiating the adaptive immune response. The epithelial residents of dendritic cells are Langerhans cells, which serve as the "sentinels" of the mucosa, altering the immune system not only to pathogen entry but also of tolerance to self antigen and commensal microbes. Oral mucosal Langerhans cells are capable of engaging and internalizing a wide variety of pathogens and have been found responsive to nickel in patients with nickel allergies, oral Candida species, oral lichen planus, lichenoid drug eruptions, graft versus host diseases, periodontal diseases median rhomboid glossitis, human immunodeficiency virus infection, hairy leukoplakia of the tongue, and oral squamous cell carcinoma. Review focuses on the role of antigen-presenting cells in particular Langerhans cells to better understand the mechanisms underlying immune responses. In this review, comprehensive detail about mucosal diseases has been compiled using the PubMed database and through textbooks.

Pathophysiology of Langerhans cells

Langerhans cells (LCs) were first described by Paul Langerhans, in 1868, as dendritically shaped cells, which were located in the squamous epithelia of epidermis. Later on, these cells were identified in all stratified squamous epithelium of mammals. Dendritic cells (DCs) play an important role in local defense mechanisms in the epithelium. LCs are situated usually in the suprabasal layer of stratified squamous epithelia of oral mucosa and epidermis of skin. They constitute 3% of the cell population in epidermis. LCs are thought to act as antigen presenting cells (APCs) during initiation of immune responses. With the help of APCs, the lymphocytes are able to recognize and respond to specific microbes. In this paper we have reviewed the origin, distribution, demonstration and mechanism of action of LCs and their role in different pathological conditions.

Immunopathogenesis of oropharyngeal candidiasis in human immunodeficiency virus infection

Oropharyngeal and esophageal candidiases remain significant causes of morbidity in human immunodeficiency virus (HIV)-infected patients, despite the dramatic ability of antiretroviral therapy to reconstitute immunity. Notable advances have been achieved in understanding, at the molecular level, the relationships between the progression of HIV infection, the acquisition, maintenance, and clonality of oral candidal populations, and the emergence of antifungal resistance. However, the critical immunological defects which are responsible for the onset and maintenance of mucosal candidiasis in patients with HIV infection have not been elucidated. The devastating impact of HIV infection on mucosal Langerhans' cell and CD4(+) cell populations is most probably central to the pathogenesis of mucosal candidiasis in HIV-infected patients. However, these defects may be partly compensated by preserved host defense mechanisms (calprotectin, keratinocytes, CD8(+) T cells, and phagocytes) which, individually or together, may limit Candida albicans proliferation to the superficial mucosa. The availability of CD4C/HIV transgenic mice expressing HIV-1 in immune cells has provided the opportunity to devise a novel model of mucosal candidiasis that closely mimics the clinical and pathological features of candidal infection in human HIV infection. These transgenic mice allow, for the first time, a precise cause-and-effect analysis of the immunopathogenesis of mucosal candidiasis in HIV infection under controlled conditions in a small laboratory animal.

Langerhans cell-like dendritic cells in the cornea, tongue and oesophagus of the chicken (Gallus gallus)

Langerhans cells are dendritic leucocytes which reside mainly within stratified squamous epithelia of skin and mucosa. Their visualization requires the use of ATPase histochemistry, electron microscopy for identifying the unique trilaminar cytoplasmic organelles (the Langerhans cell granules or Birbeck granules), and the expression of major histocompatibility complex class II molecules. Following uptake of antigen, Langerhans cells migrate via the afferent lymphatics to the lymph nodes and undergo differentiation from an antigen-processing cell to an antigen-presenting cell. Using the same approach as that employed in previous studies for the identification of chicken epidermal Langerhans cells, we show here the presence of ATPase-positive and major histocompatibility complex class II-positive Langerhans cell-like dendritic cells at the mucosal surface of the eye, tongue and oesophagus of the chicken. Ultrastructurally, these cells qualified as Langerhans cells except that they lack Langerhans cell granules. Thus, as in mammalian skin and mucosa, chicken mucosa contains mucosal dendritic cells with morphological and phenotypical features for the engagement of incoming antigens within epithelium and lamina propria.

Immunohistological and morphometric analysis of intra-epithelial lymphocytes and Langerhans cells in healthy and diseased human gingival tissues

Periodontal diseases are histologically characterized by an infiltration of several inflammatory cell populations into the gingival epithelium and connective tissue, associated with degradation of extracellular matrix components. The purpose of this in situ study was to evaluate the inflammatory state of gingival tissues by the number of intra-epithelial lymphocyte (IEL) subsets and the area fraction (AA%) occupied by collagen fibres in the upper gingival connective tissue, and also to evaluate the number of CD1a+ Langerhans cells (LC) in order to show correlation(s), if any, between these histological findings. The gingival samples were from 10 clinically healthy controls (group C), 8 patients with gingivitis (group G) and 9 with chronic adult periodontitis (group P). A quantitative evaluation of the number of cell populations (CD1a+, CD45RB+, CD3+, CD8+, CD20+, TIA-1+ and GrB+ cells) and the area fraction (AA%) occupied by collagen fibres in the upper gingival connective tissue was made by morphometric and automated image analysis. The results showed that, compared with group C, all IEL subset numbers were significantly increased (p<0.05) in G and P groups, CD20+ excepted. In addition, there was a significant increase in the cytotoxic TIA-1+ IEL number (p<0.05) in group P when compared with group G. The study also showed a significant decrease in the number of CD1a+ LC in groups G and P (p<0.02 and p<0.001, respectively) when compared with group C. No significant difference was found in CD1a+ LC number between groups G and P. The determination of coefficients of correlation (r) with data obtained for each patient showed that in group G, CD1a+ LC number was significantly correlated with CD45RB+ (p<0.05) and CD3+ (p<0.01) IEL numbers whereas during periodontitis, CD1a+ LC number was significantly and inversely correlated with CD20+ (p<0.01), cytotoxic TIA-1+ (p<0.01) and with activated cytotoxic GrB+ (p<0.01) IEL numbers. Moreover, in group P a significant (p<0.05) positive correlation was shown between CD1a+ LC number and the AA% occupied by collagen fibres. This work demonstrates a decrease in CD1a+ LC number according to the severity of the periodontal disease estimated by the number of IEL and by the area fraction occupied by collagen fibres in human gingiva. The decrease of such cells could represent a way to avoid immune overstimulation.

Acquired resistance and persistence of Candida albicans following oral candidiasis in the mouse: a model of the carrier state in humans

In our experimental model of oral candidiasis in the CD1 mouse, the primary infection showed reproducible Candida overgrowth kinetics with a peak level on day 5 of the infection. After day 7, the population stabilized at about 300 colony-forming units per excised mucosal tissue. The primary infection triggered an inflammatory response that resolved in under 8 days. At this point, the histological pattern of the mucosa reached a new equilibrium between recruited and resident mononuclear cells. The primary infection also rapidly stimulated cellular immunity, as measured from day 4 by a delayed-type hypersensitivity footpad reaction. Following a second topical challenge with Candida 30 days after the primary infection, the infection was barely detectable and a typical local delayed-type hypersensitivity reaction occurred between 24-72 h. It is proposed that acquired resistance, in conjunction with low-level persistence of Candida in our model, mimics the carrier state in sensitized humans.

Langerhans cells: structure, function and role in oral pathological conditions

Langerhans cells (LCs) are dendritic bone marrow derived cells situated suprabasally in most stratified squamous epithelia, such as the epidermis and the epithelium of oral mucosa, including the gingiva. Langerhans cells are thought to act as antigen-presenting cells (APC) during induction of immune responses. The exact role of Langerhans cells in the oral mucosa is not fully understood although several investigations suggest that these cells are involved in reactions to antigen challenge under both normal and pathological situations. In this paper the structure, phenotypic markers and derivation of Langerhans cells are reviewed. In view of recent findings, the immunological characteristics and the implications of Langerhans cells in pathologic oral reactions are discussed.

Lymphoid tissue in rat oral mucosa: structure and function

Lymphocyte and macrophage/dendritic cell populations in the oral cavity of the rat were studied by immunohistochemistry. Furthermore, the reactivity of the oral mucosa towards antigen and its position in the mucosal immune system was investigated by staining antibody-forming cells and comparing serum and saliva antibody titres. Although numerous lymphocytes and non-lymphoid cells were present in the oral mucosa, organized lymphoid tissue could not be found. The majority of the lymphocytes are T cells, particularly of the T-helper phenotype. Macrophages were found only in the connective tissue, whereas dendritic cells also occurred in the epithelium. The possible functions of the cells in the different sites of the oral mucosa are discussed. Antibody-forming cells were mainly detected in the draining superficial and posterior cervical lymph nodes and in the submandibular glands. The roles of the various compartments of the oral mucosal immune system are discussed with particular reference to the epithelium and connective tissue as induction sites, the draining lymph nodes as sites of proliferation and differentiation, and the submandibular glands as effector sites.

Tissue distribution and cytofluorometric analysis of oral mucosal T cells in the BALB/c mouse

The incidence and distribution of Thy-1.2+, Lyt-2.2+ and L3T4+ cells in the murine oral mucosa were investigated using qualitative and quantitative approaches. From immunostaining of frozen tissue sections, it appeared that the majority of oral T cells are located either in the epithelium or within the minor salivary gland network. The occurrence of Thy-1.2+, L3T4+ and Lyt-2.2+ cells at these sites points to two strategic lines of defence in the event of mucosal infections or aggression. A quantitative analysis of oral T-cell subsets was made possible by optimizing an enzymatic digestion procedure which preserves all three T-cell surface markers. Flow cytometric analysis of oral mucosal cells demonstrated that the helper phenotype is about twice as numerous as the cytotoxic/suppressor phenotype in the mucosa. Furthermore, in single cell suspensions, virtually all Thy-1+ cells were either L3T4+ or Lyt-2.2+ in the mucosa and in the spleen. From this frequency analysis and our previous studies, we conclude that T cells are a major component of the oral immune system, being 2-3 times as numerous as B cells or macrophages. Present data on the spatial distribution and characteristic ratio of T-cell subsets assess the basal activity of the local T-cell populations in healthy animals and lay the basis for comparative studies of both qualitative and quantitative variations occurring during mucosal infections or autoimmune reactions.

Regional variation in Langerhans cell distribution and density in normal human oral mucosa determined using monoclonal antibodies against CD1, HLADR, HLADQ and HLADP

The distribution, density and activation of Langerhans cells (LC) has been established in biopsies of normal human buccal mucosa, hard palate, lateral border and dorsum of tongue, floor of mouth and lip taken from sudden death post mortems. LC were identified in cryostat sections with monoclonal antibodies against CD1, HLADR, HLADQ and HLADP using an immunoalkaline phosphatase technique. The use of post mortem material was validated by comparison with biopsies taken from volunteers. LC were predominantly situated in the basal and immediately suprabasal layers of the epithelium. In floor of mouth, lip, lateral border and dorsum of tongue the cells were found along the length of the epithelium. In buccal mucosa, although LC showed fundamentally a similar distribution, a tendency to cluster around the connective tissue papillae was also noted. In hard palate LC were found parallel to the surface in the mid zone of the epithelium. No evidence of LC free areas was found. Dorsum of tongue had the highest density of LC per mm epithelial surface length (28.3 cells per mm) which was significantly greater (P less than 0.05) than buccal mucosa (25.2) which in turn had significantly more cells (P less than 0.05) than lip (22.4). The lowest density of LC was found in lateral border of tongue (17.6), hard palate (17.6) and floor of mouth (16.7). These sites had significantly fewer cells than lip, buccal mucosa and dorsum of tongue (P less than 0.05). Class II MHC molecules are necessary for antigen presentation and in all sites except buccal mucosa there was no significant difference between the number of cells expressing CD1, HLADR, HLADQ and HLADP.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantification and distribution of lymphocyte subsets and Langerhans cells in normal human oral mucosa and skin

Normal human oral (check) mucosa was studied to discover whether the oral cavity resembles the Mucosal Immune System (MIS) or the Skin Immune System (SIS). Immunophenotypes of lymphocyte subsets and Langerhans cells (LC) with their exact locations in the epithelium and papillary layer of the normal buccal mucosa were determined and compared with data of normal human skin. In a double staining procedure, the distribution of T-lymphocytes in relation to blood and lymph vessels was determined. Immunophenotyping of LC was done with a CD1a monoclonal antibody. In contrast to the skin, T-lymphocytes in buccal mucosa are not primarily perivascular in location. They are more or less randomly distributed on both sides of the basement membrane. The epithelium of the buccal mucosa contains about 37 times as many T-lymphocytes as the epidermis of normal skin. T-cell numbers in the papillary layer are more or less comparable. The CD4/CD8 ratios of about 1/2 in the epithelium of buccal mucosa and 1/4 in the skin indicates preferential presence of the CD8 subset in both sites, but the helper/inducer T-lymphocytes play a much greater role in the epithelium of the buccal mucosa when compared with skin. B-lymphocytes were not found in the epithelium and papillary layer of the buccal mucosa. Thus, immune response associated cells in buccal mucosa do not show the MIS pattern since B cells are absent. It has more in common with SIS but differences are also apparent. In the epithelium of the buccal mucosa the density of LC does not differ significantly from that of the skin, but the papillary layer of the buccal mucosa contains significantly fewer LC than the skin. As in the skin most of the LC of the buccal mucosa are found in the epithelium.

Langerhans cells in oral epithelium of chronically inflamed human gingivae

This study describes the histopathological features and the distribution of oral epithelial Langerhans cells in 19 gingival biopsies originating from an adult Tanzanian population characterized by very poor oral hygiene and severe gingival inflammation. Light-microscopically, all biopsies contained often large inflammatory connective tissue infiltrates, 6 of which predominantly contained plasma cells while the rest were dominated by lymphocytes. Seven specimens contained peculiar accumulations of round lymphoid and dendritic cells in the lower cell layers of the oral epithelium. These phenomena have not previously been demonstrated in human gingiva and deserve further attention in studies on the pathogenesis of periodontal diseases. Immuno-histochemical staining with OKT6, OKT4 and OKT8 antibodies showed markedly increased numbers of OKT6-positive cells in 7 specimens and clusters of OKT4- and OKT8-positive cells in the oral epithelium of 4 specimens. High numbers of OKT6-positive cells were not related to the presence of intra-epithelial, non-keratinocyte infiltrates or large connective tissue infiltrates. The variable numbers of oral epithelial Langerhans cells may therefore result from different bacterial antigens elucidating different responses or, alternatively, reflect different responses to similar plaque antigens penetrating the surface of the oral epithelium.

Distribution of Langerhans cells in clinically healthy human gingival epithelium with special emphasis on junctional epithelium

Twenty-one biopsies of clinically healthy marginal gingiva from children, who performed conventional oral hygiene but received no additional professional prophylaxis, were studied in order to obtain information on distribution and density of Langerhans cells (LC) in the oral gingival epithelium (OGE), the sulcular epithelium (SE) and the junctional epithelium (JE). A simple freeze-separation technique was found to create acceptable histomorphology of JE in specimens obtained adherent to teeth, while partially and non-adherent ones were rejected. The majority of LC in OGE were highly dendritic and stained intensively with OKT6 monoclonal antibodies. The distribution was network-like with a density of 21.0 +/- 3.2 LC/0.1 mm2 cross-sectional epithelial area. A similar although less dense distribution was found in SE (8.6 +/- 3.0 LC/0.1 mm2). These observations confirm previous findings. In JE 2 groups of LC were identified: 1) Weakly stained LC with very few and short dendrites distributed in a scattered way (2.8 +/- 1.4 LC/0.1 mm2) in the apical three-fourths of JE in most specimens. Present evidence suggests that these cells might be immature cells of Langerhans lineage. 2) Clusters of LC (9.4 +/- 2.9 LC/0.1 mm2) with dendrites of moderate lengths and numbers and a varied fluorescence intensity; they were found in a few specimens in the coronal one-fourth of JE and at the border zone to SE. Such clusters might represent genuine variation in the distribution of LC or reactions to initial/early plaque formation.

T-lymphocyte and Langerhans cell distribution in normal and allergically induced oral mucosa in contact with nickel-containing dental alloys

An in vivo comparison was made between the contact allergic stomatitis-inducing capacity of nickel, nickel-containing dental alloys and a non-corrosive precious metal. Fifteen patients with a positive allergic skin reaction to nickel were divided into 3 groups (A, B and C). The patients in Group A (n = 4) were fitted with an intra-oral corrosion-resistant nickel-chromium Alloy A; the patients of Group B (n = 5) received a more corrosion prone nickel-chromium Alloy B and in Group C (n = 6) strongly corroding pure nickel was used. A corrosion-resistant foil of pure palladium was placed on the contralateral side. Reactivity of pure nickel foil was also tested on the skin in Group C. Immunohistological examination of the oral mucosa on the test and reference sides was performed with monoclonal antibodies directed against T-lymphocyte subsets and Langerhans cells (LC). The results showed that at the pure nickel site the LC did increase significantly in the connective tissue (approx. 4X) of the oral mucosa. However, statistical analysis of all 6 patients of Group C together showed no corresponding increase of LC in the epithelium at the site with the pure nickel, although a numerical increase of LC was noted in the epithelium adjacent to the pure nickel foil in 2 patients, which was remarkable. It can be concluded from statistical analysis that both the reference foils and the test foils can influence the number of suppressor/cytotoxic T-lymphocytes in the connective tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

The presence of bacteria in the oral epithelium in periodontal disease. III. Correlation with Langerhans cells

Langerhans cells (LC) are cell types found in the skin and gingiva. LC have immunological functions as phagocytic cells and as antigen-presenting cells for T and B lymphocytes. Sections from biopsies of the gingiva in cases of periodontal disease were found to have increased numbers of LC. These biopsies also contained intragingival bacteria. Serial sections of frozen specimens of human gingiva were prepared for staining. Hematoxylin and eosin were used for tissue survey, the Gram stain for assessment of bacterial invasion, anti-Leu-6 monoclonal antibody associated with peroxidase technique (PAP) to identify LC, antibacterial sera to Bacteroides gingivalis and Actinobacillus actinomycetemcomitans associated with peroxidase to specifically identify these two common periodontopathogenic bacteria. Additional positive identification of bacteria was performed by preparing the same histological section containing gram-stained particles for scanning electron microscope and transmission electron microscope LC confirmation. The results suggest that the increased number of LC seen in diseased sites of oral epithelium containing intragingival microorganisms may be one of the host immune mechanisms to penetration by bacteria.

Age-associated changes in Langerhans cells of murine oral epithelium and epidermis

Oral mucosa and skin of older individuals are immunologically less responsive to a range of allergens, but it is not known whether this is due to changes in the number of Langerhans cells or to impaired cell function. EDTA-separated epithelial sheets from the cheek and palate mucosa, and from ear aN< footpad skin of three-month-old and 24-month-old C57BL/6NNia mice were stained for ATPase, beta-glucuronidase activity and Iab-surface antigen to demonstrate Langerhans cells. The general distribution of such cells was unchanged with age, but those in epithelia from the old mice were more varied in shape, with irregular celL bodies and more elongated dendritic processes. The numerical density of Langerhans cells in old mice was reduced by 30-59 per cent compared with that in young mice.

Pattern of distribution of T lymphocytes, Langerhans cells and HLA-DR bearing cells in normal human oral mucosa

The tissue distribution of helper/inducer and suppressor/cytotoxic T cells, Langerhans cells (LC) and HLA-DR bearing cells was determined in normal oral mucosa by use of monoclonal antibodies OKT4, OKT8, OKT6 and OKIa1, respectively. OKT4+ and OKT8+ cells were invariably present in normal oral epithelium and in the lamina propria. OKT8+ cells were consistently seen inside the basal cell layer of the epithelium. The distribution of LC in oral epithelium showed regional variation. In palatal epithelium LC were evenly distributed in the basal half of the epithelium, whereas in buccal mucosa the highest concentration of LC was seen in the epithelium overlying the tips of connective tissue papillae. OKIa1 stained dendritic cells in the epithelium and plump cells with small dendritic processes in the connective tissue. Some of the latter were located close to the basal cells of the epithelium. The consistent relationship between immunocompetent cells and the epithelium of the oral mucosa suggests the presence of a local immunologic defence barrier in the oral mucosa.

Modulation of HLA-DR antigens in the gingival epithelium in vitro by heat-killed Fusobacterium nucleatum and E. coli lipopolysaccharide

The in vitro influence of the periodontopathic organism Fusobacterium nucleatum (FN) on gingival tissue was examined using an organ culture system. Treatment of gingival explants obtained from periodontally diseased sites with suspensions of FN, stimulated the expression of HLA-DR antigens by Langerhans cells (LC) in a dose-dependent fashion, and produced a maintenance of the LC markers T6 and ATPase. Similar effects were seen when E. coli lipopolysaccharide (LPS) was substituted for suspensions of FN. With both FN and LPS the expression of HLA-DR by gingival keratinocytes was maintained throughout the 72-h culture period, despite the cytotoxic effects of these agents. Using a variety of immunohistological techniques and a monoclonal antibody specific for the strain of FN used, it was possible to demonstrate the uptake of FN antigens by LC within the gingival epithelium.

An example of the use of quantitation in histological diagnosis by a comparison of normal human cheek mucosa and cheek mucosa affected by lichen planus

As an example of the use of quantitation in histological diagnosis the features of normal human cheek mucosa (NHCM) and non-ulcerative lichen planus of the cheek mucosa (LPCM) have been systematically studied and quantified in order to establish normal and pathological features which are constant. The technique enabled the quantitative verification of previously held concepts relating to NHCM and LPCM. A number of interesting features which have been given little attention in past literature were also noted. It is proposed that a reliable quantifiable range of characteristic histological features should be established for use in diagnosis where possible rather than relying on the subjective approach currently employed.

The ultrastructure of initial changes in hapten-exposed rat oral mucosa

The experimentally induced cell-mediated immune reaction has been examined ultrastructurally in rat oral mucosa, using DNCB/DNFB as haptens. In skin-presensitized animals, an increased number of mononuclear cells was found in the epithelium at a very early phase (15-60 min) after hapten exposure. In nonsensitized animals, an increased number of cells was evident in hapten-exposed tissue also very early in the reaction. Mononuclear cells appeared in the connective tissue but very few in the epithelium. Interaction between mononuclear cells and Langerhans cells could be demonstrated in both experimental groups.

The pathological significance of Langerhans cells in oral cancer

The functional role of Langerhans cells (LCs) in oral cancer was studied, based on a quantitative analysis of LCs in squamous cell carcinomas arising from the tongue. LCs were identified by their positiveness for S100-protein and other cytological characters based on PAP method. LCs increased in number in the cancer region and showed an intimate relationship with lymphocytes in terms of their number and distribution. Moreover, in those cases with many LCs, clusters consisting of LCs and lymphocytes were often found to combine into "hydropic degeneration-like" lesions as seen in allergic disease such as dermal lichen planus. These findings, as well as the review of literature, suggested some immunological role of LCs in oral carcinoma.

Identification of Langerhans cells in human gingival epithelium

The purpose of this study was to qualitatively compare three recent techniques of Langerhans cells detection in oral epithelium and to quantitatively compare Langerhans cells in clinically normal and clinically inflamed human gingival biopsies. Eleven subjects were selected who displayed chronic periodontitis and moderate gingival inflammation. A quadrant associated with clinically inflamed tissues was not treated, while the remaining teeth were scaled and root-planed. Two gingival biopsies were taken: clinically normal, treated tissue; and clinically inflamed, untreated tissue. Langerhans cells were stained using HLD-DR, S-100 and OKT6. They were quantitated using a standard grid for OKT6-stained sections only. Approximately 5 times as many Langerhans cells were identified in the biopsy specimens of clinically inflamed human gingiva as in clinically normal gingiva of the same patient. Of the methods studied, OKT6 was qualitatively determined to be the best for visualization of these cells. An immunologic role in the host response to chronic periodontal disease is postulated for Langerhans cells.

Recent advances in oral mucosal research

Major progress in investigation of the normal structure and function of the oral mucosa has been made within the last ten years and has come principally from the application of various techniques developed in basic science disciplines to specific mucosal problems. However, it is apparent that many gaps still exist in our knowledge of the oral mucosa and, although it is to be expected that different workers will have distinct views on which of these are the most significant, some basic areas for further investigation can clearly be identified. For example, little is known about epithelial control systems and their disturbance by epithelial disease processes, about the nature of the interactions occurring during development and maintenance of the oral mucosal epithelia, or about the epithelial cell surface and its role in normal function. The specific properties and behavior of the cell populations of the subepithelial connective tissues appears to be poorly understood and the existence and significance of functional changes in mucosa with age and malnutrition are uncertain. It is increasingly apparent that successful progress in such investigations involves approaches using diverse methodologies. For example, epithelial-mesenchymal interactions are likely to involve multiple mesenchymal factors acting in concert to establish and maintain epithelial form and, because of this complexity, the nature of the inductive influences is not likely to be elucidated in model systems unless individual variables can be rigidly controlled. Defining the cellular and acellular elements in mesenchyme and reconstructing a functional mesenchyme from purified components may not be a simple task, but with current methods for cultivating mucosal keratinocytes and fibroblasts, as well as for purifying various components of the ground substance, it should be possible to initiate such a program of study. Some of the most dramatic advances made over the past 5-6 years in epidermal research have come about through the utilization of newly developed biochemical investigative techniques, examples of which include the use of gene cloning to study the organization of the keratin gene family, and the use of immuno-fluorescence with monoclonal antibodies to discern when various keratin proteins appear during differentiation.(ABSTRACT TRUNCATED AT 400 WORDS)

Association between plaque accumulation and Langerhans cell numbers in the oral epithelium of attached gingiva

After gingival health had been achieved in four subjects they were instructed to cease all oral hygiene measures. At 0, 8 and 21 days Plaque and Gingival Indices were recorded and gingival biopsies were removed from the buccal aspect of a first molar. Frozen sections of the gingival oral epithelium were stained for ATPase and 5'-nucleotidase to determine the number of Langerhans cells in a defined cross-sectional area. It was found that, as plaque accumulated, there was a statistically significant increase in the number of Langerhans cells in oral epithelium, particularly in the stratum spinosum. These results indicate that dental plaque can elicit a response in Langerhans cells located in the oral epithelium of the gingiva.

Epithelial and interepithelial mitoses of the oral mucosa: light and electron microscopic study in mice after exposure to different antigens

Many epithelia respond to exogenous injurious agents with an increased proliferation. Until now interepithelial cells (neuroectodermal cells, lymphocytes, cerebriform cells and Langerhans cells) have been neglected in investigations of the proliferation kinetics of stratified squamous epithelia. In mice with different antigenic exposure, and in T-cell deficient nude mice mitoses in the oral epithelium were counted by light microscopy and the proportion of mitoses of interepithelial cells was determined by an additional ultrastructural analysis. NMRI mice raised in "germ-free" and "specific pathogen-free" environments exhibit decreased mitotic rates in lingual and buccal epithelia (16 mitoses per 1000 basal cells) when compared with mice raised in "normal" environments. NMRI mice exposed orally to Candida albicans exhibit increased mitotic rates in the same 2 epithelial sites (35 mitoses per 1000 basal cells after 2 days). Similar changes occur in athymic nude mice. The electron microscopic observations showed that most of the mitoses occurred among keratinocytes. Only sporadic mitoses of nonepithelial cells could be observed within the epithelium. However, these amounted to less than 5% of the total of mitoses. Our results show that for proliferation kinetic studies of squamous epithelia this low proportion of interepithelial mitoses may be negligible. Interepithelial cells apparently recruit mainly from migrating cells into the epithelium, while proliferation in situ plays a secondary role. As there are no signs of a transmigration of the epithelium by interepithelial cells they must be considered a recirculating cell population.