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

The interaction between innate immunity and oral microbiota in oral diseases

INTRODUCTION

Innate immunity serves as the frontline to combat invading pathogens. Oral microbiota is the total collection of microorganisms colonized within the oral cavity. By recognizing the resident microorganisms through pattern recognition receptors, innate immunity is capable of interacting with oral microbiota and maintaining homeostasis. Dysregulation of interaction may lead to the pathogenesis of several oral diseases. Decoding the crosstalk between oral microbiota and innate immunity may be contributory to developing novel therapies for preventing and treating oral diseases.

AREAS COVERED

This article reviewed pattern recognition receptors in the recognition of oral microbiota, the reciprocal interaction between innate immunity and oral microbiota, and discussed how the dysregulation of this relationship leads to the pathogenesis and development of oral diseases.

EXPERT OPINION

Many studies have been conducted to illustrate the relationship between oral microbiota and innate immunity and its role in the occurrence of different oral diseases. The impact and mechanisms of innate immune cells on oral microbiota and the mechanisms of dysbiotic microbiota in altering innate immunity are still needed to be investigated. Altering the oral microbiota might be a possible solution for treating and preventing oral diseases.

Human periodontal ligament stem cells suppress T-cell proliferation via down-regulation of non-classical major histocompatibility complex-like glycoprotein CD1b on dendritic cells

BACKGROUND AND OBJECTIVE

Periodontal ligament stem cells (PDLSCs) from the periodontal ligament tissue were recently identified as mesenchymal stem cells (MSCs). The capabilities of PDLSCs in periodontal tissue or bone regeneration have been reported, but their immunomodulatory role in T-cell immune responses via dendritic cells (DCs), known as the most potent antigen-presenting cell, has not been studied. The aim of this study is to understand the immunological function of homogeneous human STRO-1⁺ CD146⁺ PDLSCs in DC-mediated T-cell immune responses to modulate the periodontal disease process.

MATERIAL AND METHODS

We utilized highly purified (> 95%) human STRO-1⁺ CD146⁺ PDLSCs and human bone marrow mesenchymal stem cells (BMSCs). Each stem cell was co-cultured with human monocyte-derived DCs in the presence of lipopolysaccharide isolated from Porphyromonas gingivalis, a major pathogenic bacterium responsible for periodontal disease, in vitro to examine the immunological effect of each stem cell on DCs and DC-mediated T-cell proliferation.

RESULTS

We discovered that STRO-1⁺ CD146⁺ PDLSCs, as well as BMSCs, significantly decreased the level of non-classical major histocompatibility complex glycoprotein CD1b on DCs, resulting in defective T-cell proliferation, whereas most human leukocyte antigens and the co-stimulatory molecules CD80 and CD86 in/on DCs were not significantly affected by the presence of BMSCs or STRO-1⁺ CD146⁺ PDLSCs.

CONCLUSIONS

This study unveiled an immunomodulatory role of STRO-1⁺ CD146⁺ PDLSCs in negatively regulating DC-mediated T-cell immune responses, demonstrating their potential to be utilized in promising new stem cell therapies.

Relationship between chemokines and dendritic cells in human chronic periodontitis

BACKGROUND

The purpose of this study was to evaluate the relationship between chemokines and dendritic cells (DCs) in human chronic periodontitis (CP).

METHODS

Gingival samples were obtained from 23 individuals with CP, and six samples of normal mucosa (NM) overlapping the third molar were used to control for the chemokine levels. Periodontal examination was conducted. Immunohistochemistry was performed for Factor XIIIa(+) and cluster of differentiation (CD)1a(+) immature DCs and CD83(+) mature DCs. Levels of the CC chemokine ligand (CCL)2, CCL3, CCL5, CCL19, CCL20, and CXC chemokine ligand (CXCL)8 were measured in gingival tissues using enzyme-linked immunosorbent assay. Inflammatory infiltrate, DCs, chemokines, classification of human CP, and clinical parameters were correlated and compared.

RESULTS

The expression of CCL2 and CCL20 was positively correlated with increased densities of CD1a(+) DCs. CCL3 and CXCL8 were positively related to the clinical attachment level. CCL3, CCL5, CCL19, and CXCL8 levels increased in the gingival samples of patients with CP compared with NM, whereas CCL20 levels increased in advanced CP compared with mild-moderate CP.

CONCLUSIONS

More CD1a(+) immature DCs are related to CCL2 and CCL20. CCL3 and CXCL8 chemokines are related to a greater severity of human CP.

Pro-inflammatory, Th1, Th2, Th17 cytokines and dendritic cells: a cross-sectional study in chronic periodontitis

There are a limited number of studies correlating the different stages of dendritic cells (DC) maturation with cytokines in individuals presented chronic periodontitis (CP). The aim of the study was to evaluate the correlation among the expression of IL-2, IL-10, IL-4, IL-6, IFN-, TNF-α, and IL-17A with the presence of DC and mild-moderate or advanced CP. Gingival samples were obtained from 24 individuals with CP and six samples of normal mucosa (NM) overlapping third molar for controls of the levels of cytokines. Periodontal examination was performed. Immunohistochemical staining was carried out, revealing CD1a+ immature, Fator XIIIa+ immature, and CD83+ mature DCs. The inflammatory infiltrate was counted, and the cytokines were measured by flow cytometry. Densities of DCs and inflammatory infiltrate, cytokines, subtypes of CP, and clinical periodontal parameters were correlated and compared. IL-6 expression was correlated positively with the increased numbers of CD1a+ immature DCs. Levels of IL-2, TNF-α, IFN-, IL-10, and IL-17A were increased when compared with NM. The percentage of sites with clinical attachment level (CAL)>3 were positively correlated with densities of inflammatory infiltrate and negatively correlated with densities of immature DCs. IL-6 can contribute to the increase of the immature DCs in the CP. Higher levels of IL-2, TNF-α, IFN-, IL-10, and IL-17A cytokines were observed in CP. Higher densities of inflammatory infiltrate as well as lower densities of immature DCs can result in a more severe degree of human CP.

Dendritic cells of the oral mucosa

The oral cavity contains distinct mucosal surfaces, each with its own unique distribution of dendritic cell (DC) subsets. In addition to tissue-specific properties, such organization might confer differential immune outcomes guided by tissue-resident DCs, which translate in the lymph node into an overall immune response. This process is further complicated by continual exposure and colonization of the oral cavity with enormous numbers of diverse microbes, some of which might induce destructive immunity. As a central cell type constantly monitoring changes in oral microbiota and orchestrating T-cell function, oral DCs are of major importance in deciding whether to induce immunity or tolerance. In this review, an overview of the phenotype and distribution of DCs in the oral mucosa is provided. In addition, the role of the various oral DC subsets in inducing immunity vs. tolerance, as well as their involvement in several oral pathologies is discussed.

Langerhans cells down-regulate inflammation-driven alveolar bone loss

Excessive bone resorption is frequently associated with chronic infections and inflammatory diseases. Whereas T cells were demonstrated to facilitate osteoclastogenesis in such diseases, the role of dendritic cells, the most potent activators of naive T cells, remains unclear. Using a model involving inflammation-driven alveolar bone loss attributable to infection, we showed that in vivo ablation of Langerhans cells (LCs) resulted in enhanced bone loss. An increased infiltration of B and T lymphocytes into the tissue surrounding the bone was observed in LC-ablated mice, including receptor activator of NF-κB ligand (RANKL)-expressing CD4(+) T cells with known capabilities of altering bone homeostasis. In addition, the absence of LCs significantly reduced the numbers of CD4(+)Foxp3(+) T-regulatory cells in the tissue. Further investigation revealed that LCs were not directly involved in presenting antigens to T cells. Nevertheless, despite their low numbers in the tissue, the absence of LCs resulted in an elevated activation of CD4(+) but not CD8(+) T cells. This activation involved elevated production of IFN-γ but not IL-17 or IL-10 cytokines. Our data, thus, reveal a protective immunoregulatory role for LCs in inflammation-induced alveolar bone resorption, by inhibiting IFN-γ secretion and excessive activation of RANKL(+)CD4(+) T cells with a capability of promoting osteoclastogenesis.

HIV-1 reactivation in HIV-latently infected dendritic cells by oral microorganisms and LPS

Dendritic cells are critical components of the host defense system that play pivotal role in linking innate immunity to adaptive immune responses. In the role of interfacing with pathogens through the action of surface pattern-recognition receptors, dendritic cells are a potential target for retroviral infection and latency. Dendritic cells are a long-lived reservoir of latent virus in HIV (human immunodeficiency virus)-infected patients. It is hypothesized that HIV-latently infected dendritic cells would be stimulated by oral bacteria leading to reactivation of HIV. In our HIV-latently infected dendritic cell models, of both promoter activation and HIV production, significant differences were observed among the bacterial species in their ability to stimulate HIV reactivation. The experimental data support the hypothesis that oral bacteria related to periodontal infections could trigger latently infected dendritic cells in gingival tissues and contribute to HIV recrudescence and undermining anti-retroviral therapy.

Effect of smoking on Langerhans and dendritic cells in patients with chronic gingivitis

BACKGROUND

Previous literature showed contrasting results regarding dendritic cell (DC) counts in patients with periodontal diseases. Although smoking decreases the number of DCs in the lungs, the effect of smoking on the quantitative distribution of Langerhans cells (LCs) and DCs in patients with chronic gingivitis has not been investigated to our knowledge.

METHODS

Gingival samples were obtained from 30 patients (15 smokers and 15 non-smokers). Immunohistochemical staining was performed to identify CD1a+ immature LCs and CD83+ mature DCs. The inflammatory infiltrate was evaluated and counted. Densities of cells were calculated within the oral epithelium (OE), sulcular epithelium (SE), and lamina propria (LP) for CD1a+ cells and within the LP for CD83+ cells. Results were compared between groups. This study evaluates whether the high number of cigarettes and smoking years affects densities of cells. Correlations among densities of LCs and DCs with densities of inflammatory infiltrate, number of cigarettes, and smoking years were performed.

RESULTS

Densities of inflammatory infiltrate and CD1a+ cells from the SE and LP were significantly lower for smokers than for non-smokers (P <0.05). This result could not be identified for CD1a+ cells from the OE and for CD83+ cells from the LP. The number of cigarettes and smoking years did not affect densities of cells. No statistically significant correlations could be drawn among densities of LCs and DCs and inflammatory infiltrate, number of cigarettes, and smoking years.

CONCLUSION

Smoking proved to affect the quantitative distribution of LCs and DCs in patients with chronic gingivitis.

Effects of oral commensal and pathogenic bacteria on human dendritic cells

BACKGROUND/AIMS

The oral cavity harbors a diverse and complex microbial community. Bacteria accumulate on both the hard and soft oral tissues in sessile biofilms and engage the host in an intricate cellular dialog, which normally constrains the bacteria to a state of commensal harmony. Dendritic cells (DCs) are likely to balance tolerance and active immunity to commensal microorganisms as part of chronic inflammatory responses. While the role played by DCs in maintaining intestinal homeostasis has been investigated extensively, relatively little is known about DC responses to oral bacteria.

METHODS

In this study, we pulsed human monocyte-derived immature DCs (iDCs) with cell wall extracts from pathogenic and commensal gram-positive or gram-negative oral bacteria.

RESULTS

Although all bacterial extracts tested induced iDCs to mature and produce cytokines/chemokines including interleukin-12p40, tumor necrosis factor-alpha, and monocyte chemoattractant protein-1 (MCP-1), the most important factor for programming DCs by oral bacteria was whether they were gram-positive or gram-negative, not whether they were commensal or pathogenic. In general, gram-negative oral bacteria, except for periodontopathic Porphyromonas gingivalis, stimulated DC maturation and cytokine production at lower concentrations than gram-positive oral bacteria. The threshold of bacteria needed to stimulate chemokine production was 100-fold to 1000-fold lower than that needed to induce cytokines. In addition, very low doses of oral commensal bacteria triggered monocytes to migrate toward DC-derived MCP-1.

CONCLUSION

Oral commensal and pathogenic bacteria do not differ qualitatively in how they program DCs. DC-derived MCP-1 induced in response to oral commensal bacteria may play a role, at least in part, in the maintenance of oral tissue integrity by attracting monocytes.

Do Langerhans cells behave similarly in elderly and younger patients with chronic periodontitis?

OBJECTIVE

The purpose of this study was to compare the number, the distribution and the expression of markers of maturation of Langerhans cells (LC) in elderly and younger patients with chronic periodontitis in order to evidence the effect of aging on LC in inflammatory gingival tissue.

METHODS

Gingival tissue specimens presenting chronic periodontitis from 8 elderly patients aged >75 (group E) and from 8 younger patients aged 50-60 (considered as controls, group C) were used for immunohistochemistry with monoclonal antibodies against CD45RB (leucocytes), CD1a (LC), markers of LC maturation (DC-LAMP, CD83) and number of immunolabelled cell subsets was evaluated using image analysis.

RESULTS

The difference in the number of CD45RB+ leucocytes in the upper connective tissue between groups was not significant. In group E, the number of CD1a+ LC was significantly decreased (P<0.002) in the epithelium and significantly increased (P<0.0004) in the upper connective tissue. Furthermore, in group E, intraepithelial CD1a+ LC are more often observed in the upper epithelium and their dendritic processes were shorter and less numerous. Concerning the expression of markers of maturation, the numbers of intraepithelial DC-LAMP+ cells and CD83+ cells were significantly increased (P<0.0007 and P<0.02, respectively) in group E.

CONCLUSION

During chronic periodontitis in elderly patients, the decrease in the number of intraepithelial LC and the alteration of dendritic processes could be balanced by a cellular distribution often observed in the upper epithelium associated with changes in cell maturation in response to bacterial elements.

Dendritic cells at the oral mucosal interface

The mucosal lining of the respiratory and digestive systems contains the largest and most complex immune system in the body, but surprisingly little is known of the immune system that serves the oral mucosa. This review focuses on dendritic cells, particularly powerful arbiters of immunity, in response to antigens of microbial or tumor origin, but also of tolerance to self-antigens and commensal microbes. Although first discovered in 1868, the epidermal dendritic Langerhans cells remained enigmatic for over a century, until they were identified as the most peripheral outpost of the immune system. Investigators' ability to isolate, enrich, and culture dendritic cells has led to an explosion in the field. Presented herein is a review of dendritic cell history, ontogeny, function, and phenotype, and the role of different dendritic cell subsets in the oral mucosa and its diseases. Particular emphasis is placed on the mechanisms of recognition and capture of microbes by dendritic cells. Also emphasized is how dendritic cells may regulate immunity/tolerance in response to oral microbes.

Ultrastructural determination of gingival Langerhans cells in alloxan-induced diabetic rats

The ultrastructure of Langerhans cells has not been fully investigated in diabetes-associated gingival tissues. The present study was carried out to investigate the ultrastructure of gingival Langerhans cells in alloxan-induced diabetic rats. Gingival biopsies were obtained from 22 diabetic and 18 control rats. Langerhans cells were observed by transmission electron microscopy (TEM) in the basal layers of healthy oral epithelium. On rare occasions, Langerhans cells were found in the suprabasal layers of the oral epithelium. Langerhans cells in the oral epithelium of diabetic rats were seen in the basal and suprabasal layers. Usually, Langerhans cells had clear cytoplasm and convoluted or indented nuclei and few or no specific granules. The clear cytoplasm contained mitochondria, lysosomes and a small number of rough-surfaced endoplasmic reticulum regions, but it lacked tonofilament. Occasionally, centrioles were also observed in the cytoplasm. The membrane of Langerhans cells had no junctional complexes such as desmosomes. In diabetic rats, Langerhans cell precursors were developed into specific granule-bearing cells. Both Langerhans cells and their granules were more frequent in the gingiva of diabetic rats than in the control group. These data suggest that Langerhans cells play an important role in explaining the pathogenesis and development of diabetic gingivitis.

Correlation of c-erbB-2 and S-100 expression with the malignancy grading and anatomical site in oral squamous cell carcinoma

An immunohistochemical analysis of 32 cases of oral squamous cell carcinoma (eight in the inferior lip, eight in the lateral angle of the tongue, eight in the palate and eight in the mouth floor) was performed to evaluate the expression pattern of c-erbB-2 protein and S-100-positive cells in the lesions. The immunohistochemical expression was correlated with the tumour anatomical site and histological grading of malignancy. A higher frequency of c-erbB-2-positive cases was found in the tongue, even though no correlation could be detected between the protein expression and the tumour histological grading. With respect to the S-100-positive cells, it was observed that a quantitative decrease was present in the cases classified as high-grade tumours when compared to the low ones (P = 0.0007). Thus, c-erbB-2 immunohistochemical expression is correlated with anatomical localization, and the expression of the S-100 Langerhans' cell markers is decreased significantly in high-grade carcinomas.

Lamina propria dendritic cells express activation markers and contact lymphocytes in chronic periodontitis

BACKGROUND

Dendritic cells are characterized by shape, structure, and membrane molecule expression; they contact T lymphocytes to present antigens and stimulate plasma cell differentiation in vitro. Dendritic cells are known to be present in healthy human gingiva and to be altered in HIV-associated periodontitis. Here, we address the phenotype, location, and intercellular relationships of dendritic cells in chronic periodontitis.

METHODS

Biopsies from patients with chronic periodontitis were analyzed by electron microscopy and indirect immunofluorescence for dendritic cells and lymphocyte markers.

RESULTS

Langerhans' cells were spread in oral epithelium but restricted to the basal layer in pocket epithelium; they did not usually express major histocompatibility complex (MHC)-II antigens nor contact lymphocytes. Dendritic cells were abundant in the lamina propria of pocket epithelium; they were MHC-II positive, admixed with CD4-positive and CD8-positive T lymphocytes, and, they expressed CD54, CD80, and CD86. Dendritic cells often contacted lymphocytes and were also located within plasma cell aggregates.

CONCLUSIONS

The data suggest that prerequisites for mounting a T cell-mediated immune response exist in chronic periodontitis, although this response is limited to the lamina propria. These results suggest that T-cell responses offer limited protection and can contribute to tissue damage during periodontal disease.

Mature dendritic cells infiltrate the T cell-rich region of oral mucosa in chronic periodontitis: in situ, in vivo, and in vitro studies

Previous studies have analyzed the lymphoid and myeloid foci within the gingival mucosa in health and chronic periodontitis (CP); however, the principal APCs responsible for the formation and organizational structure of these foci in CP have not been defined. We show that in human CP tissues, CD1a(+) immature Langerhans cells predominantly infiltrate the gingival epithelium, whereas CD83(+) mature dendritic cells (DCs) specifically infiltrate the CD4(+) lymphoid-rich lamina propria. In vivo evidence shows that exacerbation of CP results in increased levels of proinflammatory cytokines that mediate DC activation/maturation, but also of counterregulatory cytokines that may prevent a Th-polarized response. Consistently, in vitro-generated monocyte-derived DCs pulsed with Porphyromonas gingivalis strain 381 or its LPS undergo maturation, up-regulate accessory molecules, and release proinflammatory (IL-1beta, PGE(2)) and Th (IL-10, IL-12) cytokines. Interestingly, the IL-10:IL-12 ratio elicited from P. gingivalis-pulsed DCs was 3-fold higher than that from Escherichia coli-pulsed DCs. This may account for the significantly (p < 0.05) lower proliferation of autologous CD4(+) T cells and reduced release of IFN-gamma elicited by P. gingivalis-pulsed DCs. Taken together, these findings suggest a previously unreported mechanism for the pathophysiology of CP, involving the activation and in situ maturation of DCs by the oral pathogen P. gingivalis, leading to release of counterregulatory cytokines and the formation of T cell-DC foci.

Quantitative morphological analysis of Langerhans cells in healthy and diseased human gingiva

Langerhans cells (LC) are implicated in the initiation and maintenance of inflammatory periodontal diseases. The purpose of this immunohistological study using morphometric and automated image analysis was to determine the morphological features of CD1a+ LC in healthy and inflammatory gingiva according to their localisation in the upper epithelium or the basal layer. The study was on gingival samples from 11 healthy controls (C), eight patients with gingivitis (G) and 12 patients with severe chronic adult periodontitis (P). The results show that in the basal layer of all experimental groups, the perimeter, surface and equivalent diameter of CD1a+ LC were significantly decreased (P<0.005) when compared with those in the upper epithelium of the same group. Furthermore, CD1a+ LC had become more rounded, reflected by a significant increase in form factor (P<0.005), when located close to the epithelial basal membrane. In the upper epithelium of group P, the perimeter, surface and equivalent diameter of CD1a+ LC were significantly decreased (P<0. 05) and the form factor significantly increased (P<0.05) when compared with the upper epithelium of group C. This work provides evidence for important morphological variations in CD1a+ LC according to their location within the epithelium and the severity of the periodontal disease. The observed morphological changes may reflect a cellular adaptation during the epithelial transmigration and could eventually be involved in immune stimulation during periodontitis.

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.

Evidence and a novel hypothesis for the role of dendritic cells and Porphyromonas gingivalis in adult periodontitis

We have proposed a novel overall hypothesis and approach to understanding the pathophysiology of adult periodontitis, one of the most common diseases that afflicts the US population. While mortality of the dentition is the most familiar outcome of adult periodontitis, its links with other more severe diseases, including coronary artery disease, respiratory diseases and pre-term labor, cannot be ignored. We have called attention to the many intriguing parallels between adult periodontitis and contact hypersensitivity (CHS). CHS is among the most common of dermatoses that afflicts mankind and one of the most intensively studied of in vivo immune responses. Both adult periodontitis and CHS target the host integument (gingiva or skin) and appear to involve the activation and sensitization of similar subsets of antigen capture and presenting cells, the dendritic cells (DCs), as well as similar T cell subsets. DCs have been termed "nature's adjuvant", being more efficient at antigen-presentation than macrophages or B cells and the only antigen-presenting cells that can stimulate naïve T cells to proliferate. This immunostimulatory capacity can also have detrimental effects for the host, as typified by graft-vs.-host disease and CHS responses. Both AP and CHS involve a predominantly destructive T cell response mediated by both regulatory and effector T cells. In the present paper, we show intriguing evidence that Porphyromonas gingivalis is a unique pathogen in this regard, able to infect, sensitize and activate DCs in vitro and, probably, in situ. Many questions about the role of P. gingivalis-sensitized DCs in adult periodontitis, and of the parallels between adult periodontitis and CHS, however, remain to be answered.

Density of CD1a-labeled Langerhans' cells in normal human gingiva and in nifedipine- and immunosuppressive medication-induced gingival overgrowth

BACKGROUND

The purpose of this study was to compare the distribution of Langerhans' cells in normal human gingiva and in nifedipine- and immunosuppressive medication-induced gingival overgrowth by means of an immunohistochemical study.

METHODS

Gingival samples were collected from 11 nifedipine-medicated cardiac patients, 22 triple-medicated (azathioprine, prednisolone, and cyclosporin A) renal transplant recipients, and 28 generally healthy individuals. Patients were grouped into the immunosuppression group, the combined immunosuppression and nifedipine group, the nifedipine group, and the generally healthy control group. Five microm-thick cryostat sections were stained with monoclonal antibody (mAb) for CD1a using an avidin-biotin-enzyme complex (ABC) method. Numbers of CD1a-labeled cells/mm2 were determined in 6 areas: oral epithelium, oral sulcular epithelium, sulcular epithelium, middle connective tissue, connective tissue beneath the oral epithelium, and connective tissue beneath the sulcular epithelium. Significances of differences between the groups were tested by means of the Kruskall-Wallis test, and significances of differences between pairs of results by the Mann-Whitney U-test and the t test.

RESULTS

Numbers of CD1a-labeled cells were significantly lower in the medicated groups than in controls in all 3 epithelial areas (P <0.0001) and in the connective tissue beneath the sulcular epithelium (P <0.0021). There were significantly fewer CD1a-labeled cells in the sulcular epithelium in the nifedipine group than in the other medication groups.

CONCLUSIONS

The reduced numbers of CD1a-labeled cells found in nifedipine-induced gingival overgrowth were similar to the reduced numbers of CD1a-labeled cells in gingival overgrowth associated with immunosuppressive medication.

Expression of CD1a monocytes cultured with supernatants from periodontally diseased gingival epithelial cells

Langerhans cells are believed to originate from the monocyte lineage and have been reported to increase in number with plaque accumulation and gingival inflammation. The aim of this study was to investigate the effects of local gingival epithelial factors on the induction of CD1a, a Langerhans cell phenotype, on monocyte rich populations.

MATERIALS AND METHODS

Peripheral blood monocyte rich in populations from healthy subjects were cultured for 24 h with either healthy gingival or periodontally diseased gingival epithelial supernatants. Additionally, the monocyte rich populations were cultured with cytokines IL-I alpha, IL-I beta, IL-6 and TNF-alpha which are known to be produced by epithelial cells or co-cultured with autologous epithelial cells. The per cent CD1a positive cells was determined using FACS analysis.

RESULTS

Healthy gingival supernatants did not induce CD1a expression in monocyte rich populations, however, a significant increase in per cent CD1a+ cells for monocyte rich populations cultured with five (P < 0.01) of six periodontal gingival epithelial supernatants was found. IL-I alpha or TNF-alpha (10 ng/well) resulted in a significant increase in the per cent CD1a+ cells (P < 0.01). Depletion of CD1a+ Langerhans cells from healthy gingival epithelium did not enhance induction of CD1a expression in monocyte rich populations. Monocyte rich populations cultured together with non-depleted epithelial cultures resulted in a decreased per cent of CD1a+ cells.

CONCLUSION

These findings indicated that epithelial factor/s associated with periodontally involved epithelia, may be involved in inducing a Langerhans cell phenotype in monocyte rich populations. The data also provide indirect evidence for a role of Langerhans cells in inhibiting induction of CD1a in healthy epithelium.

Human gingival keratinocytes express E-selectin (CD62E)

OBJECTIVES

E-selectin (CD62E) is an adhesion molecule that participates in the binding of leukocytes to activated blood vascular endothelium. The present study was undertaken to characterise the pattern of E-selectin expression on epithelial cells of the gingival crevice and oral epithelium.

METHODS

A panel of six anti-E-selectin monoclonal antibodies was reacted with cryosections of human gingiva and cytospins of cultured gingival keratinocytes.

RESULTS

Three antibodies raised against leukocyte binding epitopes of the molecule (H4/18, H18/7, 1.2B6) were reactive with gingival keratinocytes, three were negative (4D10, BBA1, BBA2), while all six reacted with endothelial cells. Staining with H18/7 and 1.2B6 was weaker and more variable than with H4/18. In cell culture, levels of E-selectin expression reduced slowly, and were only modestly increased by treatment with exogenous TNF alpha, a known inducer of E-selectin on endothelium.

CONCLUSIONS

E-selectin epitopes are expressed on gingival keratinocytes. These binding epitopes may be involved in the traffic of leukocytes in this tissue compartment.

Oral mucosal Langerhans' cells

Langerhans' cells (LC) are dendritic, antigen-presenting cells present within the epithelium of skin and mucosa, including that of the oral cavity. This article reviews the literature on the phenotypic and functional features of oral mucosal Langerhans' cells, and speculates on other aspects by extrapolating from data on their epidermal counterparts.

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.

Quantitative evaluation of Langerhans cells in median rhomboid glossitis

Langerhans cells (LC) serve as antigen presenting cells and provide immune surveillance within epithelia. Since depression of LC number and/or function may allow tolerance to antigens, we evaluated LC in median rhomboid glossitis (MRG), a condition linked to persistent candidal infection of lingual mucosa. Material included a total of 36 cases of MRG (7 of which did not show PAS + fungi) and 6 controls. LC were identified by their expression of S-100 and HLA-DR antigens and quantified using image analysis. Equal numbers of LC were identified using S-100 + and HLA-DR + markers. The density of LC (cells/mm of basement membrane, mean +/- SD) in both PAS + MRG (2.6 +/- 1.3) and PAS-MRG (3.0 +/- 1.7) was markedly depressed compared with controls (17.2 +/- 6.4), (P less than 0.001). These findings indicate that the LC network is perturbed in MRG, and are consistent with the view that of localized defect in immune surveillance may contribute to persistent fungal infection of the oral mucosa.

Langerhans cells in human chronic gingivitis and phenytoin-induced gingival hyperplasia

Langerhans cell numbers in oral epithelium increase as dental plaque accumulates. The anti-convulsant drug phenytoin predisposes to gingival hyperplasia in certain patients who take this medication for epilepsy and who also have poor oral hygiene. In this study 7 patients with phenytoin-induced gingival hyperplasia were compared with 5 subjects with chronic marginal gingivitis. On initial examination and on completion of the hygiene phase of periodontal therapy (a period ranging from 3.0 to 4.25 months), clinical indices of plaque and gingivitis were recorded and biopsies were taken from the lower anterior labial gingiva. Frozen sections were stained by an immunoperoxidase technique using the monoclonal antibody OKT6, and the number of Langerhans cells in a defined cross-sectional area was counted. In phenytoin-induced gingival hyperplasia there was a marked increase in Langerhans cells (13.8 +/- 0.45) when compared with chronic gingivitis (7.7 +/- 0.31; p less than 0.05). Both groups showed marked reductions in their plaque and gingival indices and numbers of Langerhans cells once treatment had been completed. However, levels of Langerhans cells in the drug-induced hyperplasia remained significantly higher (3.5 +/- 0.26) than in chronic gingivitis (1.5 +/- 0.22; p less than 0.05).

Immunohistochemical study of neurochemical markers in gingiva obtained from periodontitis-affected sites

Immunohistochemical methods have been used to study the occurrence of neuronal markers in human gingiva from periodontitis-affected sites. In periodontitis-affected buccal gingiva densely distributed neurofilament (NF)-immunoreactive (IR) fiber bundles were observed in the deeper parts of the propria, while NF-IR single fibers occurred in the superficial propria and occasionally in the buccal epithelium. Periodontitis-affected gingiva obtained from interproximal sites showed only sparsely distributed NF-IR fibers. Single nerve fibers immuno-reactive to the peptides substance P and calcitonin gene-related peptide occurred close to or within the epithelium in both buccal and interproximal gingiva. Around blood vessels neuropeptide Y-, peptide histidine-isoleucine amide- and vasoactive intestinal polypeptide-IR fibers were occasionally observed, while clusters of gamma-melanocyte-stimulating hormone-IR cells were found in the propria, in addition to gamma-melanocyte-stimulating hormone IR nerve fibers. Somatostatin-IR dendritic cells were seen in epithelium and propria of buccal and interproximal gingiva, although a high variability in the number of SOM-IR cells was observed. All neuronal markers studied showed a similar distribution in material obtained from young patients with clinically healthy gingivae, although the number of NF-IR fibers in the propria in these subjects was lower. The results demonstrate that in gingiva obtained from periodontitis-affected sites several different biologically active peptides occur in both nerve fibers and cells. At least some of these substances could possible play a role in the inflammatory process. However, since clinically normal gingiva was shown to contain nerve fibers and cells expressing immunoreactivity to the substances studied, no unique periodontitis-induced expression of the neuronal markers studied was found. Thus, any alteration of these substances during the periodontitis process remains to be elucidated.

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.

Comparison of NK-cell (Leu-7+ and Leu-11b+) populations in clinically healthy gingiva, chronic gingivitis and chronic adult periodontitis

Various investigations have reported the presence of cytotoxic lymphocyte activity in inflammatory periodontal disease. The collective evidence indicates that the inflammatory infiltrates of gingivitis and periodontitis should feature a major component of large granular lymphocytes (NK-cells) possessing cytotoxic potential. Thus, the purpose of this study was to determine and compare, by use of immunohistochemical methods, the numbers of NK-cells in biopsies of clinically healthy gingiva, chronic gingivitis and chronic adult periodontitis and their relationship, if any, to the T- and B-lymphocyte populations. Gingival biopsies were obtained from 8 patients in each of three disease groups selected on the basis of predetermined clinical criteria. Using the avidin-biotin immunoperoxidase technique, four consecutive serial sections from each biopsy specimen were stained with a panel of antihuman monoclonal antibodies for T-lymphocytes (UCHL-1) B-lymphocytes (CD-45R), and NK-cells (Leu-7 and Leu-11b). Analyses of variance yielded a statistically significant main effect for each cell immunophenotype. The Newman-Keuls Sequential Range Test showed statistically significant differences for all but two mean comparisons (p less than 0.01). The comparisons for UCHL-1 and Leu-7 between chronic gingivitis and periodontitis specimens did not demonstrate significance. Although T- and B-lymphocyte populations increased approximately 20 x progressing from healthy to gingivitis to periodontitis specimens, the NK-cell population showed only a 3 x increase which represented 19%, 6.6% and 7% of the total of all positively stained lymphocytes across biopsy groups.

Human gingival Langerhans cells as accessory cells in mitogen induced T cell responses

Peripheral blood and gingival tissue was collected from patients undergoing surgery for the treatment of periodontal disease. Both unfractionated peripheral blood mononuclear cells and a T cell-enriched, monocyte-depleted lymphocyte population were isolated from the blood samples while a gingival epithelial cell suspension was prepared from the oral aspect of the gingival tissue. The blood cells (1 X 10(5)) were then co-cultured with the gingival epithelial cells (1 X 10(5) and 1 X 10(4)) in 200 microliters aliquots in microtitre trays for three days to see if the epithelial cells could act as accessory cells in the lymphocyte response to the mitogen, phytohaemagglutinin (PHA). Lymphocyte proliferation was assessed by measuring the uptake of [6-3H] thymidine during the last 18 hours of culture. Removal of monocytes from peripheral blood mononuclear cells led to a significant, but not total, reduction in the proliferative response to PHA. When gingival epithelial cells were added to the T cells they restored their response to PHA in a dose dependent fashion. As Langerhans cells were the only potentially immunocompetent cells seen in the epithelial cell suspensions, it is concluded that these cells are acting as accessory cells in the T cell response to PHA.

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.

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.

An immunohistochemical study of oral lichen planus

Specimens from 22 cases of oral lichen planus were prepared for studies of the basement membrane zone by immunohistochemical and histochemical methods. Langerhans' cells, monocytes, and lymphocytes constitute the predominant cells of the inflammatory infiltrate, thus indicating a cell-mediated response. Lymphocyte-related necrosis of epithelium and nonspecific vasculitis are associated with an altered basement membrane zone. Immunoproteins, including IgG, IgA, IgM, and C'3 as well as fibrinogen, are present and distributed in a nonspecific pattern.

Differential distribution of ATPase- and T6-positive cells (Langerhans cells) in the limbus and cornea of Hereford and non-Hereford cattle

Epithelial sheets from the limbus, cornea, and third eyelid of Hereford and non-Hereford cattle were examined for the presence of Langerhans cells (LC) using the membrane enzyme ATPase as a marker for LC. The aim of the study was to test the hypothesis that differences in LC density exist between the various ocular epithelia of these animals producing depressed immune surveillance in the case of Hereford cattle. The presence of LC in ocular tissues was confirmed by parallel studies which detected epithelial cells bearing T6, an antigen expressed by human LC. Studies using serial sections demonstrated that T6+ cells also reacted with an anti-human HLA-DR monoclonal antibody. The detection of T6+, DR+ and ATPase+ cells in ocular epithelium in the absence of infiltrating macrophages suggested that LC are present in these tissues. While there were no significant differences in the density of T6+ cells between non-Hereford and Hereford cattle, in the latter ATPase+ cells were significantly fewer in the lateral, medial, and upper limbus.

S-100 immunolabelling of Langerhans cells in oral epithelium

Langerhans cells (LCs) are dendritic cells usually present in the suprabasal regions of squamous epithelia remarkable by the presence of Fc IgG and C3 receptors, Ia/Dr, T-6 and T-4 antigens on their membranes. Conventional and immunohistochemical techniques for identification of LCs require special fixation procedures and are incompatible with paraffin embedding. A method for staining LCs, in routine fixed and paraffin-embedded material, based on the use of antiserum against S-100 proteins is presented. The problem arising from the simultaneous staining of melanocytes is discussed. S-100 positive dendritic cells should be considered as LCs when fulfilling 3 criteria: located in the suprabasal layers of the epithelium; the whole cell body being visible; with at least one dendritic process.

Experimental gingivitis in relation to susceptibility to periodontal disease. II. Phase-contrast microbiological features and some host-response observations

In the present investigation, a number of histological and immunohistochemical characteristics of periodontal tissues as well as the phase-contrast microscopy of dental plaque were studied after experimentally-induced gingival inflammation in relation to susceptibility to periodontal disease. The study included a younger (mean age 34.1 years) and an older age group (mean age 48 years) with a reduced but healthy periodontium. Both age groups had the same amount of loss of attachment which may suggest that they had different degrees of susceptibility to periodontal disease. At the start of the experiment, each patient was instructed to abstain from oral hygiene in one quadrant of the mouth for a period of 18 days. At the end of the 18-day period, supra-gingival plaque and gingival tissue samples were taken. As determined by phase-contrast microscopy, the plaque samples of both age groups contained relatively high proportions of spirochetes. This may indicate that the patients are at risk for recurrence of periodontal breakdown. The general histopathologic picture of the gingival tissue samples of both age groups was similar to the so-called 'early lesion'. However, IgA-producing plasma cells were found in most tissue samples of both age groups. The first part of this study showed that the younger, in comparison to the older, patients developed inflammation in terms of bleeding on probing more rapidly. These clinical results cannot be explained by the host-parasite parameters investigated in the present study.

Immunohistological identification of cell subsets in human gingiva after local treatment for gingivitis or periodontitis

The cellular infiltrate present in human diseased gingiva was analyzed in biopsies from 12 patients with gingivitis or periodontitis. The samples studied had been obtained in the course of surgery at inflammatory sites remaining after institution of periodontal treatment. Histological and immunological techniques were used to identify macrophages, B-cells, plasma-cells, T-cells and T cell subsets, as well as cells expressing class II HLA membrane antigens. T-cells appeared as the predominant population, but plasma-cells were also visualized in nearly all samples. Both OKT4+ and OKT8+ cells were seen in all cases, the latter being more numerous in periodontitis patients. Interdigitating-like cells were observed, positively labelled for class II antigens, as well as macrophages which were more numerous in periodontitis patients. These results suggest the participation of all components of the immune response in gingival disease, in a way resembling chronic recurrent inflammatory diseases.

Oral mucosal Langerhans cells express DR and DQ antigens

The expression of the Class II antigens HLA-DR and HLA-DQ in human oral mucosa was examined in health and in the presence of inflammation. DQ antigens were detected on dendritic intra-epithelial cells which expressed the Langerhans cells (LC) phenotype T6+, DR+. In healthy gingiva, DR and DQ were co-expressed on Langerhans cells, whereas in an experimental gingivitis (day 8), more LC expressed DR than DQ. Absolute LC numbers were increased in inflammation. Traumatic ulceration of the buccal mucosa resulted in a decrease in the density of T6-, DR-, and DQ-positive cells. Repopulation of migrating and regenerated epithelium was complete 10 days after ulcer induction. Disparity between DR and DQ expression was seen in both normal buccal mucosa and throughout the ulcer healing period. These results are in agreement with the reported sequence of Class II antigen expression on lymphoid cells.

The ultrastructure of human gingival Langerhans cells in health and disease

There was a statistically significant shift towards increased proportions of type I Langerhans cells (containing many Langerhans-cell granules) and reduced proportions of both type II Langerhans cells (containing few granules) and indeterminate cells in diseased oral epithelium when compared to healthy oral epithelium. Langerhans cells and indeterminate cells were also seen in the sulcular epithelium of healthy and diseased specimens but never in junctional or pocket-lining epithelium.

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.