Gamma delta T lymphocytes in human periodontal disease tissue

Bite-sized immunology; damage and microbes educating immunity at the gingiva

Immune cells residing at the gingiva experience diverse and unique signals, tailoring their functions to enable them to appropriately respond to immunological challenges and maintain tissue integrity. The gingiva, defined as the mucosal barrier that surrounds and supports the teeth, is the only barrier site completely transected by a hard structure, the tooth. The tissue is damaged in early life during tooth eruption and chronically throughout life by the process of mastication. This occurs alongside challenges typical of barrier sites, including exposure to invading pathogens, the local commensal microbial community and environmental antigens. This review will focus on the immune network safeguarding gingival integrity, which is far less understood than that resident at other barrier sites. A detailed understanding of the gingiva-resident immune network is vital as it is the site of the inflammatory disease periodontitis, the most common chronic inflammatory condition in humans which has well-known detrimental systemic effects. Furthering our understanding of how the immune populations within the gingiva develop, are tailored in health, and how this is dysregulated in disease would further the development of effective therapies for periodontitis.

Immunologic burden links periodontitis to acute coronary syndrome: levels of CD4 + and CD8 + T cells in gingival granulation tissue

OBJECTIVE

To investigate the proportional variation of macrophage and T-lymphocytes subpopulations in acute coronary syndrome (ACS) patients, its association with periodontitis (P), and to compare with control individuals.

SUBJECTS AND METHODS

Three groups of subjects participated: one group consisted of 17 ACS patients with P (ACS + P), another group consisted of 22 no ACS + P patients, and a control group consisted of 23 participants with gingivitis (no ACS + G). Macrophage, CD4 + , and CD8 + T-lymphocytes and CD4 + /CD8 + ratio values in gingival tissue were determined histometrically.

RESULTS

Significant differences were found among three groups regarding the mean number of macrophage (no ACS + P > ACS + P > no ACS + G; p < 0.05) and CD8 + T-lymphocytes (no ACS + P > ACS + P > no ACS + G; p < 0.05). Significant variations were observed between the groups both CD4 + T-lymphocytes densities (ACS + P > no ACS + P and ACS + P > no ACS + G; p < 0.05) and CD4 + / CD8 + ratio (no ACS + P < no ACS + G and ACS + P < no ACS + G; p < 0.05).

CONCLUSIONS

The increased number of CD8 + T-lymphocytes in both group ACS + P and group no ACS + P resulted in a reduction of the CD4 + /CD8 + ratio in gingival tissue when compared with no ACS + G group.

CLINICAL RELEVANCE

The decrease of CD4 + /CD8 + ratio in gingival tissue reflects periodontitis and may be associated with severe adverse outcomes in people with ACS.

Sex-Related Effect of Aging in Gingival Gamma-Delta T Cells

Aging affects the number and function of gamma-delta (γδ) T cells in a tissue-specific manner, modifying the risk for inflammatory disease. These aging-related γδT-cell variations in gingival tissues that could increase the risk for inflammation and periodontal disease remain unknown. Here we sought to identify quantitative and qualitative variations in gingival γδT cells associated with aging that could have an impact in oral immunoinflammatory responses. For this, gingival tissues from young (4 mo) and aged (24 mo) male and female mice were collected and analyzed by flow cytometry. Cell suspensions were stimulated and stained with eFluor450 (cell viability), anti-CD45 (hematopoietic cells), anti-CD3 (lymphocytes), anti-TCRγδ (γδT cells), anti-IL-15rα (cell proliferation), and anti-Notch-3 (senescence marker). Detection of intracellular cytokines IL-17A and interferon γ (IFNγ) was performed. Gingival expression of specific γ- and δ-chains and cytokines was evaluated by quantitative reverse transcription polymerase chain reaction. A significantly higher number of IL-17A-producing γδT cells and IL-17A expression levels were observed in gingival tissues from aged females but not males. Similarly, the number of gingival Notch-3+ γδT cells increased with aging only in females. IL-15rα was not detected in gingival γδT cells. Chains γ1, 2, 4, 5, 6, and 7 as well as δ1, 2, 4, and 6 were detected. Detection levels of all γ chains except γ1 as well as δ1 and δ2 changed with aging in males, females, or both. Interestingly, number of IL-17A-producing conventional T cells similarly increased with aging only in females. Both sexes showed increased IFNγ+ conventional T-cell numbers with aging; however, it reached significance only in females. In conclusion, the number of gingival IL-17A-producing γδT cells and IL-17A expression increase naturally with aging specifically in females. This sexual dimorphism in gingival γδT and conventional Th17 cell numbers and phenotypes suggests distinct aging-related mechanisms of periodontitis in males and females.

γδT cells in oral tissue immune surveillance and pathology

The oral mucosa's immune system is composed of tissue-resident and specifically recruited leukocytes that could effectively tolerate a wide range of microbial and mechanical assaults. Shortly after CD4⁺ helper T cells (TH17 cells) that produce interleukin 17 (IL-17) were identified, it was discovered that γδT cells could also induce substantial levels of this pro-inflammatory cytokine. In the past decades, it has become clear that due to a complicated thymic program of development, γδT cells frequently serve as the primary sources of IL-17 in numerous models of inflammatory diseases while also assisting in the maintenance of tissue homeostasis in the skin and intestine. But it wasn't until recently that we took thorough insight into the complex features of γδT cells in the oral mucosa. Most gingival intraepithelial γδT cells reside in the junctional epithelium adjacent to the dental biofilm, suggesting their potential role in regulating oral microbiota. However, inconsistent results have been published in this regard. Similarly, recent findings showed contradictory data about the role of γδT lymphocytes in experimental periodontitis based on different models. In addition, conflicting findings were presented in terms of alveolar bone physiology and pathology underlying the oral mucosa. This review provided an overview of current knowledge and viewpoints regarding the complex roles played by oral-resident γδT cells in host-microbiota interactions, gingivitis and periodontitis, bone physiology and pathology.

γδ T Cells Differentially Regulate Bone Loss in Periodontitis Models

γδ T cells are nonclassical T lymphocytes representing the major T-cell population at epithelial barriers. In the gingiva, γδ T cells are enriched in epithelial regions adjacent to the biofilm and are considered to regulate local immunity to maintain host-biofilm homeostatic interactions. This delicate balance is often disrupted resulting in the development of periodontitis. Previous studies in mice lacking γδ T cells from birth (Tcrd^-/- mice) examined the impact of these cells on ligature-induced periodontitis. Data obtained from those studies proposed either a protective effect or no impact to γδ T cells in this setting. Here, we addressed the role of γδ T cells in periodontitis using the recently developed Tcrd-GDL mice, enabling temporal ablation of γδ T cells. Specifically, the impact of γδ T cells during periodontitis was examined in 2 modalities: the ligature model and the oral infection model in which the pathogen Porphyromonas gingivalis was administrated via successive oral gavages. Ablation of γδ T cells during ligature-induced periodontitis had no impact on innate immune cell recruitment to the ligated gingiva. In addition, the number of osteoclasts and subsequent alveolar bone loss were unaffected. However, γδ T cells play a pathologic role during P. gingivalis infection, and their absence prevented alveolar bone loss. Further analysis revealed that γδ T cells were responsible for the recruitment of neutrophils and monocytes to the gingiva following the exposure to P. gingivalis. γδ T-cell ablation also downregulated osteoclastogenesis and dysregulated long-term immune responses in the gingiva. Collectively, this study demonstrates that whereas γδ T cells are dispensable to periodontitis induced by the ligature model, they play a deleterious role in the oral infection model by facilitating pathogen-induced bone-destructive immune responses. On a broader aspect, this study highlights the complex immunopathologic mechanisms involved in periodontal bone loss.

IL-8 as a Potential Therapeutic Target for Periodontitis and Its Inhibition by Caffeic Acid Phenethyl Ester In Vitro

Salivary levels of interleukin-8 (IL-8) are elevated in patients with periodontitis. Caffeic acid phenethyl ester (CAPE) improves the periodontal status in subjects. However, whether CAPE can reduce IL-8 expression is unclear. We collected saliva to determine proinflammatory cytokine levels and used subgingival calculus and surrounding tissues from patients with periodontitis for oral microbiota analysis via 16s ribosomal RNA gene sequencing. THP-1 cells were stimulated with sterile-filtered saliva from patients, and target gene/protein expression was assessed. IL-8 mRNA expression was analyzed in saliva-stimulated THP-1 cells treated with CAPE and the heme oxygenase-1 (HO-1) inhibitor tin-protoporphyrin (SnPP). In 72 symptomatic individuals, IL-8 was correlated with periodontal inflammation (bleeding on probing, r = 0.45; p < 0.001) and disease severity (bleeding on probing, r = 0.45; p < 0.001) but not with the four oral microbiota species tested. Reduced salivary IL-8 secretion was correlated with effective periodontitis treatment (r = 0.37, p = 0.0013). In THP-1 cells, saliva treatment induced high IL-8 expression and IKK2 and nuclear factor-κB (NF-κB) phosphorylation. However, the IKK inhibitor BMS-345541, NF-κB inhibitor BAY 11-7082, and CAPE attenuated saliva-induced IL-8 expression. CAPE induced HO-1 expression and inhibited IKK2, IκBα, and NF-κB phosphorylation. Blocking HO-1 decreased the anti-inflammatory activity of CAPE. The targeted suppression of IL-8 production using CAPE reduces inflammation and periodontitis.

Maintaining homeostatic control of periodontal bone tissue

Alveolar bone is a unique osseous tissue due to the proximity of dental plaque biofilms. Periodontal health and homeostasis are mediated by a balanced host immune response to these polymicrobial biofilms. Dysbiotic shifts within dental plaque biofilms can drive a proinflammatory immune response state in the periodontal epithelial and gingival connective tissues, which leads to paracrine signaling to subjacent bone cells. Sustained chronic periodontal inflammation disrupts "coupled" osteoclast-osteoblast actions, which ultimately result in alveolar bone destruction. This chapter will provide an overview of alveolar bone physiology and will highlight why the oral microbiota is a critical regulator of alveolar bone remodeling. The ecology of dental plaque biofilms will be discussed in the context that periodontitis is a polymicrobial disruption of host homeostasis. The pathogenesis of periodontal bone loss will be explained from both a historical and current perspective, providing the opportunity to revisit the role of fibrosis in alveolar bone destruction. Periodontal immune cell interactions with bone cells will be reviewed based on our current understanding of osteoimmunological mechanisms influencing alveolar bone remodeling. Lastly, probiotic and prebiotic interventions in the oral microbiota will be evaluated as potential noninvasive therapies to support alveolar bone homeostasis and prevent periodontal bone loss.

Development and Function of γδT Cells in the Oral Mucosa

To successfully withstand a wide variety of microbial and mechanical challenges, the immune system of the oral mucosa is composed of tissue-resident and specially recruited leukocytes. These leukocytes facilitate the establishment and maintenance of local homeostasis but are also capable to cause oral pathologies when are unrestrained. γδT cells represent an important tissue-resident innate T-cell population in various mucosal and nonmucosal barrier tissues, in which they are ideally located to assist in immunosurveillance, tissue repair, and homeostasis. Whereas most works studying γδT cells were focused on tissues such as the skin and intestine, these cells in the oral mucosa were only recently thoroughly studied. The findings obtained by those studies appear to be both complementary and contradicting, likely reflecting differences in the experimental settings and the type of transgenic mouse modalities employed by each study. Nevertheless, oral γδT cells were shown to consist of developmentally distinct tissue-resident Vγ6 cells and circulating Vγ1 and Vγ4 subsets that are independently maintained in the oral mucosa. In the gingiva, a particularly challenging barrier tissue due to its proximity to the dental plaque, γδT cells are strategically positioned close to the plaque and represent the major source of IL-17. While this suggests that γδT cells might be involved in controlling the dental biofilm, conflicting data were reported in this regard. In vivo studies have shown that γδT cells either play a protective role during age-associated bone loss or, alternatively, have no impact in this process. Also, recent reports suggested opposing data concerning the impact of γδT cells in experimental periodontitis based on the ligature model. This review summarizes and discusses the most up-to-date literature on oral γδT cells, providing a balanced perspective regarding our current understanding on the development of oral γδT cells and their role under physiologic conditions and certain oral pathologies.

Interleukin-17 and interleukin-23 levels in gingival crevicular fluid of patients with chronic and aggressive periodontitis

Introduction

Interleukin-17 is a pro-inflammatory cytokine with a wide range of protective and destructive effects in periodontitis. The role of IL-23 is stabilisation and expansion of Th-17. The aim of this study was to assess whether patients with aggressive and chronic periodontitis exhibit different gingival crevicular fluid (GCF) concentrations of IL-17 and IL-23 compared with clinically healthy subjects.

Material and methods

GCF samples were obtained from 32 patients: 10 with chronic periodontitis (CP), 12 with aggressive periodontitis (AgP), and 10 healthy controls (HC). IL-23 and IL-17 concentrations were measured using enzyme-linked immunosorbent assay (ELISA). Comparison of study groups was performed with ANOVA and Tukey HSD tests. Spearman's correlation coefficient was used to assess correlations between the variables.

Results

IL-17 concentration was significantly higher in the healthy group compared to the AgP and CP groups (p < 0.001), but there were no significant differences between the CP and AgP groups. IL-23 levels in the healthy group were significantly higher than that in the AgP group (p < 0.001). Cytokine concentrations did not correlate significantly with probing depths and clinical attachment levels.

Conclusions

Gingival crevicular fluid concentrations of IL-17 and IL-23 were significantly higher in the healthy group compared to periodontitis groups.

Microbe-specific unconventional T cells induce human neutrophil differentiation into antigen cross-presenting cells

The early immune response to microbes is dominated by the recruitment of neutrophils whose primary function is to clear invading pathogens. However, there is emerging evidence that neutrophils play additional effector and regulatory roles. The present study demonstrates that human neutrophils assume Ag cross-presenting functions and suggests a plausible scenario for the local generation of APC-like neutrophils through the mobilization of unconventional T cells in response to microbial metabolites. Vγ9/Vδ2 T cells and mucosal-associated invariant T cells are abundant in blood, inflamed tissues, and mucosal barriers. In this study, both human cell types responded rapidly to neutrophils after phagocytosis of Gram-positive and Gram-negative bacteria producing the corresponding ligands, and in turn mediated the differentiation of neutrophils into APCs for both CD4(+) and CD8(+) T cells through secretion of GM-CSF, IFN-γ, and TNF-α. In patients with acute sepsis, circulating neutrophils displayed a similar APC-like phenotype and readily processed soluble proteins for cross-presentation of antigenic peptides to CD8(+) T cells, at a time when peripheral Vγ9/Vδ2 T cells were highly activated. Our findings indicate that unconventional T cells represent key controllers of neutrophil-driven innate and adaptive responses to a broad range of pathogens.

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.

The effects of age and gender on gingival tissue and peripheral blood T-lymphocyte subsets: a study in mice

The aim of this study is to investigate the effects of age and gender on relative number of CD4+ and CD8+ T lymphocyte and CD4+/CD8+ ratios in gingival tissue and peripheral blood of periodontally healthy BALB/c mice with flow cytometric analysis. The study was carried out on periodontally healthy 60 BALB/c mice. They were separated into five groups according to the life expectancy: Group I (newborn, 1-10 days old), Group II (age at weaning, 21-28 days old), Group III (age of sexual maturity, puberty, 7-8 weeks old), Group IV (adult, 8 months old), and Group V (the aged, 14 and over). Males and females were equally represented in each group. CD4+ and CD8+ T lymphocytes and CD4+/CD8+ ratio values in gingival tissue and peripheral blood were determined using flow cytometry in the biopsy samples. The relative number of CD8+ T lymphocyte in gingival tissue was higher in puberty (p < 0.05) and the aged (p < 0.05), with more significantly difference in males (p < 0.05). The CD4+/CD8+ ratios in gingival tissue were lower in puberty group and the-aged groups compared to the other groups (p < 0.05). The peripheral blood CD4+/CD8+ ratio increased in puberty and the aged groups. These differences were more significant in females than in males (p < 0.05). There were considerable negative correlations between CD4+/CD8+ T lymphocyte ratio in gingival tissue and CD4+/CD8+ T lymphocyte ratio in peripheral blood in puberty (r = 0.647, p < 0.01) and the aged ( r = 0.599, p < 0.05). In conclusion, our data suggest that CD4+/CD8+ T lymphocyte ratios in peripheral blood increase periodontally healthy mice in puberty and the old groups, while CD4+/CD8+ T lymphocyte ratios in gingival tissue decrease in the same groups. The relative number of CD8+ T lymphocytes increases in gingival tissue in puberty and the old groups when it decreases in peripheral blood. Results from this study indicated that periodontally healthy BALB/c mice may represent important information to determine the character of an immune response in the course of a lifetime.

Inflammation associated with implants with different surface types

OBJECTIVES

The aim of this study was to determine the nature of the inflammatory infiltrate associated with different transmucosal implant surfaces in dogs.

METHODS

Three experimental and one control single-stage implants were randomly placed on each side of the jaw in eight dogs. The transmucosal portion of the test implants consisted of an acid-etched surface (type A), a machined surface with a circumferential groove (type C) and a surface prepared by mild anodic oxidation (type D). The control was a standard machined surface (type B). In order to determine the response to the different surfaces, plaque control was carried out twice weekly following placement of the implants for the entire period of the experiment. At 6 months, gingival biopsies and plaque samples were obtained. The area of inflammatory infiltrate and the nature of the infiltrating cell types were determined using immunohistology. Real-time polymerase chain reaction was used to identify putative periodontal pathogens.

RESULTS

Inflammatory infiltrates were associated with all implant surfaces and were commonly found subepithelially and perivascularly. T cells were the predominant infiltrating cell type in all lesions, associated with the different surfaces. In all lesions the CD4 : CD8 ratio was approximately 2 : 1. Statistical analysis showed that the type C surface (machined surface with a groove) had significantly larger inflammatory infiltrates than the type B surface (machined surface without a groove; P<0.05). No statistically significant differences were found with respect to the size of the inflammatory infiltrates or in terms of the nature of infiltrating cells. However, despite the intensive plaque control regime, plaque was present on all implant surfaces at the time of biopsy 6 months after placement. All implants had similar numbers of Tannerella forsythia, Fusobacterium nucleatum and Porphyromonas gingivalis. Actinobacillus actinomycetemcomitans, was not detected in any sample.

CONCLUSIONS

These results suggest that the development of inflammation associated with implants is independent of surface type, but is nevertheless associated with the presence of plaque. The different surfaces had no influence on the nature of the infiltrate, with T cells being the predominant cell type in all lesions. Finally, the different implant surface types seemed not to influence the peri-implant microbiota. However, the presence of the circumferential groove tended to be associated with larger infiltrates. Whether this is due to increased plaque accumulation remains to be determined.

The changes in T lymphocyte subsets following periodontal treatment in patients with chronic periodontitis

OBJECTIVE

The aim of this study was to determine whether there was any change in T-lymphocyte subsets in patients with chronic periodontitis after applying different periodontal treatment methods.

PATIENTS AND METHODS

Twenty-four patients with chronic periodontitis were included in the study. In every phase of the treatment (pretreatment, initial treatment, curettage and flap operations) the biopsy samples were taken from the gingival tissues at sites of chronic periodontitis. Then CD4(+) and CD8(+) lymphocyte and CD4(+)/CD8(+) ratio values were determined using flow cytometry in the biopsy samples. At the same time, gingival pocket depth, Löe-Silness gingival index, and Silness-Löe plaque index scores were recorded to assess the periodontal status in patients. To determine the correlation between the clinical measurements and the laboratory results obtained before the treatment, after initial treatment, after curettage and after flap operations, we conducted an analysis using a paired t-test.

RESULTS

Flow cytometry findings in the patients with chronic periodontitis showed that CD4(+) and CD8(+) lymphocyte values before treatment were under the normal value and the CD4(+)/CD8(+) ratio was within the normal distribution interval. The CD4(+)/CD8(+) ratio decreased postcurettage and postflap operation. This decrease was statistically significant (p < 0.001). The CD4(+) and CD8(+) lymphocyte values were increased postcurettage and postflap operation. This increase was also statistically significant (p < 0.001).

CONCLUSIONS

These findings suggest that local immune response was poor in the patients with chronic periodontitis. CD4(+) and CD8(+) T-lymphocytes could play a significant role in chronic periodontitis pathobiology.

Immune processes in periodontal disease: a review

The inflammatory and immune processes in periodontitis are complex and, although a great deal of information is available, many questions remain. Variation in human susceptibility to periodontitis has long been accepted, but the pathological basis of this is poorly understood. Similarly, we know little of the differences, if any, between the pathology of chronic and aggressive periodontitis. Genetics and environmental influences play a role in the susceptibility process, but if and how that translates through the immune and inflammatory processes to produce the plasma cell-dominated lesions seen in periodontitis remain to be elucidated. This review will focus on immunological aspects of the inflammatory changes seen in gingivitis and periodontitis, addressing both humoral and cellular responses to the microbial insult from dental plaque. A tendency for an individual or site to form an extensive plasma cell infiltrate may indicate an inability to defend against periodontopathogens and thus a predisposition to periodontitis. The issues to be considered include: 1) homing of immune and inflammatory cells to target tissues; 2) their local proliferation and synthetic activity; 3) the cytokine profile of the leukocytes; 4) the immunoglobulin subclasses of locally produced antibodies; 5) mucosal and systemic immune characteristics of the response; 6) the humoral immune response in periodontal health and disease states; and 7) the antigenic target of the immune response in periodontal lesions.

Mast cells in human periodontal disease

Recently, mast cells have been shown to produce cytokines which can direct the development of T-cell subsets. The aim of the present study was to determine the relationship between mast cells and the Th1/Th2 response in human periodontal disease. Tryptase+ mast cell numbers were decreased in chronic periodontitis tissues compared with healthy/gingivitis lesions. Lower numbers of c-kit+ cells, which remained constant regardless of clinical status, indicate that there may be no increased migration of mast cells into periodontal disease lesions. While there were no differences in IgG2+ or IgG4+ cell numbers in healthy/gingivitis samples, there was an increase in IgG4+ cells compared with IgG2+ cells in periodontitis lesions, numbers increasing with disease severity. This suggests a predominance of Th2 cells in periodontitis, although mast cells may not be the source of Th2-inducing cytokines.

The role of acquired immunity and periodontal disease progression

Our understanding of the pathogenesis in human periodontal diseases is limited by the lack of specific and sensitive tools or models to study the complex microbial challenges and their interactions with the host's immune system. Recent advances in cellular and molecular biology research have demonstrated the importance of the acquired immune system not only in fighting the virulent periodontal pathogens but also in protecting the host from developing further devastating conditions in periodontal infections. The use of genetic knockout and immunodeficient mouse strains has shown that the acquired immune response-in particular, CD4+ T-cells-plays a pivotal role in controlling the ongoing infection, the immune/inflammatory responses, and the subsequent host's tissue destruction. In particular, studies of the pathogen-specific CD4+ T-cell-mediated immunity have clarified the roles of: (i) the relative diverse immune repertoire involved in periodontal pathogenesis, (ii) the contribution of pathogen-associated Th1-Th2 cytokine expressions in periodontal disease progression, and (iii) micro-organism-triggered periodontal CD4+ T-cell-mediated osteoclastogenic factor, 'RANK-L', which is linked to the induction of alveolar bone destruction in situ. The present review will focus on some recent advances in the acquired immune responses involving B-cells, CD8+ T-cells, and CD4+ T-cells in the context of periodontal disease progression. New approaches will further facilitate our understanding of their underlying molecular mechanisms that may lead to the development of new treatment modalities for periodontal diseases and their associated complications.

Flow-cytometric analysis of T-lymphocyte subsets after different treatment methods in smokers and non-smokers with chronic periodontitis

AIM

To determine any change in T-lymphocyte subsets after applying different treatment methods in smokers and non-smokers with chronic periodontitis.

PARTICIPANTS

50 adults with chronic periodontitis.

METHOD

The subjects were divided into smokers and non-smokers. Biopsy samples were taken from the gingival pocket wall tissues at sites with chronic periodontitis before treatment, after initial treatment, after curettage and after flap operation and tested for CD4+, CD8+ lymphocyte and CD4/ CD8 ratio values. Gingival pocket depth, gingival index (GI-Löe-Silness) and plaque index (PI-Silness-Löe) scores were also recorded. Analysis aimed at determining the relation between the clinical measurements and the laboratory results.

RESULTS

Flow cytometry findings in both groups showed that CD4+ and CD8+ lymphocyte values before treatment were under the normal value while the CD4+/CD8+ ratio was within normal distribution interval. The lymphocyte values observed in the smokers were found to be lower than those in the non-smokers. After treatment the difference between the lymphocyte values in smokers and non-smokers was found to be statistically significant. However, the difference between the CD4/CD8 rate obtained in smokers and non-smokers was not found to be statistically significant.

CONCLUSIONS

The lymphocyte values observed in smokers were found to be lower than those in non-smokers after applying different treatment methods and the local immune response was poor in the smokers.

Flow-cytometric analysis of T-lymphocyte subsets after different treatment methods in patients with pericoronitis

PURPOSE

The aim of this study was to determine whether there was any change in T-lymphocyte subsets in patients with periocoronitis after the application of different treatment methods.

PATIENTS AND METHODS

Twenty-six patients with acute pericoronitis were included in the study. In every phase of the treatment (pretreatment, postcurettage, and postextraction), the biopsy samples were taken from the gingival tissues at sites of pericoronitis. Then, CD4(+) and CD8(+) lymphocyte and CD4(+)/CD8(+) ratio values were determined using flow cytometry in the biopsy samples. At the same time, gingival index (Löe-Silness) and plaque index (Silness-Löe) scores were recorded to assess the periodontal status in patients. To determine the correlation between the clinical measurements and the laboratory results obtained before the treatment, after curettage, and after extraction, we conducted an analysis using a paired t-test.

RESULTS

The normal values in peripheral blood of CD4(+) and CD8(+) lymphocytes are 25% to 29% and 19% to 48%, respectively. However, the CD4(+) and CD8(+) lymphocyte values in the patients with acute pericoronitis were found to be 22.12% +/- 6.15% and 7.69% +/- 4.12%, respectively. These values are lower than the normal values. The CD4(+) lymphocyte value increased to 31.06% +/- 7.09% postcurettage and to 32.24% +/- 3.11% postextraction. The CD8(+) lymphocyte value increased to 16.21% +/- 5.27% postcurettage and to 18.25% +/- 3.13% postextraction. The CD4/CD8 ratio increased postcurettage and postextraction. This increase was statistically significant (P <.001). Postcurettage, there was decrease in clinical indexes, which was statistically significant (P <.001). A significant correlation between CD4(+) lymphocyte and ginigival index values and also between CD8(+) lymphocyte and plaque index values was determined postcurettage (P <.05).

CONCLUSION

CD4(+) and CD8(+) T-lymphocytes could play a significant role in pericoronitis pathobiology.

The Fc gamma receptor genotype as a severity factor for chronic periodontitis in Japanese patients

BACKGROUND

Functional polymorphisms of immunoglobulin G (IgG) Fc receptors (Fc gamma R) have been shown to be associated with generalized aggressive periodontitis (GAgP) or recurrence of chronic periodontitis (CP) in Japanese patients. The purpose of this study was to evaluate whether Fc gamma R polymorphisms are also associated with severity of CP.

METHODS

Fifty Japanese non-smoking patients with severe CP and 39 Japanese non-smoking patients with moderate CP were identified according to established clinical criteria, including measurements of probing depth (PD), clinical attachment level (CAL), and alveolar bone loss (BL). Fc gamma R genotypes for 3 bi-allelic polymorphisms (Fc gamma RIIa-R/H131, Fc gamma RIIIa-158V/F, Fc gamma RIIIb-NA1/NA2) were determined in these CP patients and 64 race-matched, non-smoking healthy controls by means of allele-specific polymerase chain reactions.

RESULTS

There was a significant over-representation of Fc gamma RIIIa-158V allele in severe CP patients compared to moderate CP patients (odds ratio 2.03, 95% confidence interval [CI] 1.03-4.01, chi 2 = 4.86, P = 0.028). In addition, we found a strong association between CP severity and Fc gamma R composite genotype comprising Fc gamma RIIIa-158V plus Fc gamma RIIIb-NA2 (severe CP versus moderate CP: odds ratio 4.69, 95% CI 1.52-15.10, chi 2 = 9.35, P = 0.002; severe CP versus healthy controls: odds ratio 4.10, 95% CI 1.62-10.59, chi 2 = 11.13, P = 0.0009). Moreover, CP patients positive for the composite genotype exhibited more severe signs of periodontitis than composite genotype-negative individuals (positive versus negative; mean PD: 3.8 mm versus 3.2 mm, P = 0.005; mean CAL: 4.5 mm versus 3.7 mm, P = 0.005; mean % BL: 37.6% versus 29.9%, P = 0.008).

CONCLUSION

Our results document the Fc gamma RIIIa-158V allele and possibly Fc gamma RIIIb-NA2 to be associated with severity of CP in Japanese patients.

Involvement of T-lymphocytes in periodontal disease and in direct and indirect induction of bone resorption

Periodontal disease is a peripheral infection involving species of gram-negative organisms. T-lymphocytes can be found in the dense inflammatory infiltrate in this disease. CD4+ and CD8+ T-cells are present in periodontal lesions, as are memory/activated T-lymphocytes. In addition, Th1- and Th2-type T-lymphocytes and their associated cytokines with a subtle polarization to Th1 may be present. Th1-type T-cells up-regulate the production of pro-inflammatory cytokines IL-1 and TNF-alpha, which can induce bone resorption indirectly by promoting differentiation of osteoclast precursors and subsequently by activating osteoclasts. Such osteoclast differentiation is dependent on stimulation of osteoprotegerin ligand (OPG-L) production by osteoblastic cells. By contrast, activated T-cells, by virtue of direct production and expression of OPG-L, can directly promote osteoclast differentiation. OPG-L appears to be predominantly expressed on Th1-type cells. The direct and indirect T-cell involvement in periodontal bone resorption appears to be dependent on the degree of Th1-type T-cell recruitment into inflamed gingival tissues. This T-cell recruitment is regulated by adhesion molecules and chemokines/chemokine receptors. The adhesion molecules involved include alpha4 and alpha6 integrins, LFA-1, and ICAM-1. The Th1-type T-cells preferentially express CCR5 and CXCR3, which are found prominently in diseased gingivae. By contrast, little CCR4, expressed by Th2-type T-cells, can be detected. Also, the chemokine ligands RANTES, MIP1-alpha (both CCR5), and IP-10 (CXCR3 ligand) were elevated in inflamed periodontal tissues. The T-cell features in diseased periodontal tissues can be compared with those in rheumatoid arthritis, wherein bone resorption often attributed to Th1-type T-cell involvement has also been demonstrated.

Chemokines in human periodontal disease tissues

An immunoperoxidase technique was used to examine IP-10 (interferon-gamma inducible protein 10), RANTES (regulated on activation normal T cell expressed and secreted), MCP-1 (monocyte chemoattractant protein-1), and MIP-1 alpha (macrophage inflammatory protein-1 alpha) in gingival biopsies from 21 healthy/gingivitis and 26 periodontitis subjects. The samples were placed into 3 groups according to the size of infiltrate. MIP-1 alpha+ cells were more abundant than the other chemokines with few MCP-1+ cells. The mean percent MIP-1 alpha+ cells was higher than the percent MCP-1+ cells (P = 0.02) in group 2 (intermediate size infiltrates) lesions from periodontitis subjects, other differences not being significant due to the large variations between tissue samples. Analysis of positive cells in relation to CD4/CD8 ratios showed that with an increased proportion of CD8+ cells, the mean percent MIP-1 alpha+ cells was significantly higher in comparison with the mean percent RANTES+ and MCP-1+ cells (P < 0.015). Endothelial cells were MCP-1+ although positive capillaries were found on the periphery of infiltrates only. Keratinocyte expression of chemokines was weak and while the numbers of healthy/gingivitis and periodontitis tissue sections positive for IP-10, RANTES and MCP-1 reduced with increasing inflammation, those positive for MIP-1 alpha remained constant for all groups. In conclusion, fewer leucocytes expressed MCP-1 in gingival tissue sections, however, the percent MIP-1 alpha+ cells was increased particularly in tissues with increased proportions of CD8 cells and B cells with increasing inflammation and also in tissues with higher numbers of macrophages with little inflammation. Further studies are required to determine the significance of MIP-1 alpha in periodontal disease.

Clinical, pathological and immunological aspects of periodontal disease

The inflammatory and immune responses during the development and progression of periodontitis are reviewed. Susceptibility to periodontitis may be related to whether plasma cells predominate in the tissues of an individual, or a site, in response to the microbial insult from dental plaque. The tendency for an individual or site to form an extensive plasma cell infiltrate may indicate an inability to defend against periodontopathogenic bacteria and thus a predisposition to periodontitis. Selected pertinent areas of current interest in cellular and humoral immunology are considered within the periodontal context. These topical issues include (a) homing of immune and inflammatory cells to target tissues; (b) the local proliferation and synthetic activity of immune and inflammatory cells; (c) the cytokine profile of the inflammatory and immune cells; and (d) the immunoglobulin subclasses of locally produced antibodies.

Anti-inflammatory cytokine IL-10 and T cell cytokine profile in periodontitis granulation tissue

Th2 cells are more abundant than Th1 cells in periodontitis lesions, but the relative importance of the Th1 and Th2 subsets in periodontal disease is not understood. In addition, the role of proinflammatory and anti-inflammatory cytokines in this disease process is unclear. Biopsies were obtained from 10 patients with early onset periodontitis (EOP) and 10 patients with adult periodontitis (AP). From all of the patients in the AP group we were able to obtain and section the gingival tissue to serve as controls. We used polyclonal monospecific antibodies to detect cells expressing IL-2, IL-4, IL-6, IL-10 and IL-15, tumour necrosis factor (TNF-alpha) and interferon-gamma (IFN-gamma) in formalin-fixed, paraffin-embedded sections of granulation tissue from periodontitis lesions. We also employed a series of oligonucleotide probes to detect cells expressing the cytokine transcripts in the same tissue biopsies. Cells that expressed IL-4 or IL-6 were more numerous than cells expressing either IL-2 or IFN-gamma. Th2 cells were more numerous in EOP and AP tissues. IL-15 substitutes for IL-2 in a number of biological activities related to the Th1 immune response, and interestingly, in periodontal lesions the IL-15-expressing cells outnumbered IL-2-expressing cells, suggesting that this is the pattern of immune regulation by T cells in the periodontium. The functional balance in the T cell subsets detected by their cytokine profiles underlies the importance of the anti-inflammatory mechanisms taking place in the diseased tissue. The numbers of inflammatory leucocytes that express the anti-inflammatory cytokine IL-10 are much more widely distributed than those that express the proinflammatory cytokines IL-6 and TNF-alpha. This study suggests that large numbers of infiltrating inflammatory cells as well as accessory cells are involved in the down-regulation of the inflammatory and immune response in periodontitis.

The Fcgamma receptor genotype as a risk factor for generalized early-onset periodontitis in Japanese patients

BACKGROUND

Genetic polymorphisms of immunoglobulin G (IgG) Fc receptors (FcgammaR) were recently shown to be associated with recurrence rates of adult periodontitis (AP). The purpose of this study was to evaluate whether FcgammaR polymorphisms are also associated with generalized early-onset periodontitis (G-EOP) in Japanese patients.

METHODS

Thirty-eight Japanese patients with G-EOP and 83 Japanese patients with AP were identified according to established clinical criteria, including measurements of probing depth, clinical attachment level, and alveolar bone level. FcgammaR genotypes for 3 bi-allelic polymorphisms were determined in these G-EOP and AP patients and 104 race-matched healthy controls by means of allele-specific polymerase chain reactions.

RESULTS

There was a significant difference in the distribution of FcgammaRIIIb genotypes between G-EOP patients and healthy controls (P = 0.02). Additionally, a significant over-representation of FcgammaRIIIb-NA2 allele was observed in G-EOP patients as compared to AP patients and controls (P= 0.02, P= 0.009, respectively). Moreover, we found a strong association between G-EOP and the composite genotype comprising FcgammaRIIIb-NA2 and FcgammaRIIIa-158F (G-EOP versus controls: odds ratio 2.4, 95% CI 1.0-6.0, chi2 = 4.13, P= 0.04).

CONCLUSIONS

This study indicates that the FcgammaRIIIb-NA2 allele and possibly FcgammaRIIIa-158F could be associated with susceptibility to G-EOP in Japanese patients.

Protective and destructive immune reactions in apical periodontitis

Apical periodontitis is initiated primarily by the mixed microflora of infected root canals. Continuous flow of bacteria and their products through the apical foramen induces influx, activation and coordinated interaction of immune-inflammatory cells within the periapical area. Successful mobilization of host defense mechanisms prevents abundant extraradicular bacterial invasion. However, anti-infective effector mechanisms are not restricted to killing the invading microorganisms but also destroy normal tissue components and induce bone absorption, resulting ultimately in the loss of the affected teeth. Moreover, autocrine and paracrine loops of stimulation may lead to the perpetuation of the local inflammatory lesion and may also alter the function of remote tissues and organs. This review attempts to summarize current knowledge about the pathogenic mechanism of apical periodontitis, focusing on the formation of a special granulation tissue that effectively fights bacteria originated from the infected pulp chamber and, by exerting this protective function, also contributes to harmful local and distant events. The dynamic equilibrium between defensive and destructive mechanisms may provide a pathobiological basis for better understanding of clinical signs and symptoms of various forms of apical periodontitis lesions and influence treatment strategy and practice.

Relevance of Fc gamma RIIIa-158V-F polymorphism to recurrence of adult periodontitis in Japanese patients

The immunoglobulin receptor Fc gamma RIIIa (CD16) is distributed on natural killer (NK) cells, macrophages, and gamma delta T cells, and is polymorphic. Fc gamma RIIIa-158V has a higher affinity for both monomeric and immune complexed IgG1, IgG3, and IgG4 than IIIa-158F. We determined Fc gamma RIIIa-158V/F genotypes of Japanese patients with adult periodontitis. A significant over-representation of Fc gamma RIIIa-158F was found in patients with recurrence, compared with patients without recurrence, making Fc gamma RIIIA a candidate gene for recurrence risk of adult periodontitis.

Cytokine expression in periodontal health and disease

Soluble proteins that serve as mediators of cell function and are produced by various cell types, such as structural and inflammatory cells, are collectively called cytokines. Several lines of evidence have revealed that cytokines play important roles not only in tissue homeostasis but also in the pathogenesis of many infectious diseases. Recent research on biological activities in normal periodontium and the pathogenesis of periodontal diseases has clarified the involvement of various cytokines in the biological activities observed in the sites. Cytokines play crucial roles in the maintenance of tissue homeostasis, a process which requires a delicate balance between anabolic and catabolic activities. In particular, growth factors--such as fibroblast growth factor (FGF), platelet-derived growth factor (PDGF), insulin-like growth factor (IGF), transforming growth factor-beta (TGF-beta)--are thought to play important roles in modulating the proliferation and/or migration of structural cells in the periodontium and the production of various extracellular matrices by these cells. On the other hand, there is little doubt that excessive and/or continuous production of cytokines in inflamed periodontal tissues is responsible for the progress of periodontitis and periodontal tissue destruction. Particularly, inflammatory cytokines--such as IL-1 alpha, IL-1 beta, IL-6, and IL-8--are present in the diseased periodontal tissues, and their unrestricted production seems to play a role in chronic leukocyte recruitment and tissue destruction. It is possible that monitoring cytokine production or its profile may allow us to diagnose an individual's periodontal disease status and/or susceptibility to the disease. In addition, although the hypothesis is still controversial, it has been suggested that discrete T-cell subsets (Th1 and Th2) with different cytokine profiles play specific roles in the immunopathogenesis of periodontal diseases.

Characterization of lymphocyte subpopulations in periapical lesions by flow cytometry

The mechanisms by which the bacterial root-canal infection leads to periapical bone destruction (cysts or granulomas) are not yet well understood. Previous works have shown elements of an active immune response in the lesions. In the present study, flow cytometry was used to improve the characterization of immune cells. Semiquantitative immunohistochemical analysis showed the presence of plasma cells, macrophages and B and T cells. The simultaneous use of several antibodies in flow cytometry allowed a more precise phenotype of the lymphocytes. The cysts displayed an abundance of B lymphocytes at the same time as a relative scarcity of CD8+ cells. CD4+ lymphocytes were the dominant lymphocyte population in most cases. A small number of gamma delta T lymphocytes and natural killer cells was found. These preliminary results show that flow cytometry may be used to characterize immune cells from inflamed tissue and opens the possibility for further functional studies.

Expression of receptor beta-chain variable region by T cells in human periodontal disease

T cells play a major part in the immune response in periodontal diseases. In order to determine any selective T-cell receptor (TCR) beta-chain variable region (V beta) usage in the infiltrates of healthy/ gingivitis (H/G) and adult periodontitis (AP), cells were extracted from gingival biopsies, the CD4 and CD8 cells stained with antibodies to eight V beta regions, and two-colour flow cytometry used to analyse the data. The frequencies of CD4 and CD8 cells expressing each of the TCR-V beta families varied from 0 to 46% between individuals. A high percentage of CD4 and CD8 cells expressed the V beta 13 family in several AP biopsies, but, in a number of H/G tissues, a high percentage of T cells expressed up to three families including the V beta 13 region, these varying from individual to individual. The mean results showed a significantly greater percentage of V beta 5.2-3-positive CD4 cells (p = 0.003) and V beta 5.1- and 5.2-3-positive CD8 cells (p = 0.003 and 0.025, respectively) isolated from H/G than AP tissues. The percentage of V beta 3.1-positive CD4 cells extracted from H/G tissues was also higher but not quite significant at the 0.05 level (p = 0.051). Sections of gingival tissue in biopsies from H/G and AP were stained in situ; there were no significant differences in the mean expression of V beta 3.1-, 5.1- or 5.2-3-positive cells. A second aim was to determine the effect of Porphyromonas gingivalis on the TCR repertoire. There were no differences in the mean percentage of CD4 or CD8 cells expressing the eight TCR-V beta regions between the two groups after stimulation in vitro with P. gingivalis outer-membrane antigens. There was, however, a trend towards a decrease in the percentage of positive CD4 and CD8 T cells after culture with the antigen. This was significant for CD4 cells from H/G expressing the V beta 5.1 and 5.3 TCRs (p = 0.032 and p = 0.038, respectively). This trend was not evident for V beta 5.2-3-positive CD4 cells or V beta 5.1-positive CD8 cells isolated from both H/G and AP nor for V beta 3.1-positive CD8 cells from AP. The results show that there may be restricted V beta usage in gingival tissues, particularly in H/G tissues. The V beta 5 and 3.1 families may be selected for in the gingival tissues and may also be involved in P. gingivalis activation.

Expression of T-cell receptor Vbeta2, 6 and 8 gene families in chronic adult periodontal disease

Substantial evidence exists to suggest a role for T-cells in periodontal disease. As yet, however, the T-cell receptors remain to be characterised at the molecular level. The expression and the nucleotide sequence of genes from the T-cell receptor beta variable (TCRBV) gene families 2, 6 and 8 were analyzed in periodontal tissue from 24 patients with chronic adult periodontal disease (CAPD) and peripheral blood lymphocytes (PBL) of 16 of these patients. A restriction in the expression of these TCRBV gene families was detected in periodontal tissue from 14/24 patients with CAPD, and the pattern of gene expression was often different between individual patients; however there was no restriction in TCRBV gene expression in matched PBL samples from 8 of these 14 patients. Quantitative RT PCR analysis of samples from 5 CAPD patients who expressed all 3 TCRBV gene families in their periodontal tissues did not reveal any significant differences in the levels of gene expression in periodontal tissue and PBL. In contrast to the findings with some CAPD patients, genes from all 3 TCRBV families were always expressed in periodontal tissue and PBL from disease-free control subjects. PCR products from both the PBL and periodontal tissue of CAPD patients were cloned and sequenced; analysis of the nucleotide sequence revealed diversity with respect to the expression of TCRB joining (TCRBJ) and TCRB diversity (TCRBD) genes and the sequence of the junctional region in all samples analysed. In conclusion, in CAPD, the pattern of TCRBV gene expression in periodontal tissue is often but not always different from that in PBL and healthy periodontal tissue, which may indicate, in some cases, a local influence on particular T-cell subsets which is relevant to the pathogenesis of periodontal disease. However, the expressed TCRB genes are heterogeneous at the nucleotide level, emphasising the underlying complexity at the molecular level in the local T-cell response in CAPD.

Cell-mediated immune system regulation in periodontal diseases

The adaptive immune system consists of humoral and cell-mediated immunity. T-lymphocytes are the key components of cell-mediated immunity. CD4+ helper T-lymphocytes facilitate B-cells to differentiate and produce specific antibodies, whereas CD8+ cytotoxic T-lymphocytes kill virally infected cells. Periodontal diseases have been associated with a variety of imbalances in the regulation of immune responses. Changes in the ratios of peripheral blood CD4+ and CD8+ T-lymphocytes, depressed proliferative responses of peripheral blood lymphocytes, and increased frequency of CD45RO+ memory T-lymphocytes in diseased tissues have been reported in individuals with various forms of periodontal disease. While some studies have shown an increased frequency of gamma delta + T-cells in periodontal lesions, the role of gamma delta + T-cells in periodontal disease remains controversial. The ability of putative periodontopathic bacteria selectively to stimulate certain V beta-expressing T-cells is intriguing and could determine whether a CD4+ Th1 or a CD4+ Th2 cell response is elicited. The prominence of a particular subset of helper T-cells within the periodontal lesion could be a reflection of the stage and activity of the disease, or the types of bacteria present. Regardless, longitudinal studies of the involvement of T-cell subsets and cytokines in periodontal disease are clearly needed.

In situ localization of cell synthesis and proliferation in periodontitis gingiva and tonsillar tissue

OBJECTIVE

Previous work indicates that large numbers of B and T cells accumulate in the periodontal soft tissues although we know little about cellular synthetic activity and proliferation in this site. The aim of this study was to examine lymphocytic cell synthetic activity and proliferation in periodontitis gingiva and compare this to a known site of leucocyte proliferation, namely the oropharyngeal tonsils.

MATERIALS AND METHODS

Messenger RNA (mRNA) and 28S ribosomal (28S rRNA) expressing cells in formalin-fixed/paraffin-embedded gingival and tonsillar tissue sections were detected by in situ hybridisation (ISH) using poly-deoxyribothymidine and 28S probes respectively. In addition S-phase proliferating and cycling cells were also detected by ISH with histone probes and by Ki-67 immunohistochemistry. Ten gingival biopsy samples were obtained from adult periodontitis patients and five tonsillar biopsies from tonsillectomy patients.

RESULTS

Both mRNA and 28S rRNA-expressing cells were detected in all the samples tested. Plasma cells showed the strongest signal for the two probes and slight to moderate staining could be seen in epithelium, fibroblasts and endothelial cells. In contrast, gingival lymphocytes were either weakly stained or were unstained for these probes of synthetic activity. In tonsils, most lymphocytes in germinal centres showed moderate staining and mantol zone cells were much more weakly stained. In gingival samples, histone mRNA-expressing and cycling (Ki-67) cells were detected in 4/10, 10/10 cases respectively. These positive cells were mainly basal and suprabasal epithelial cells and a few mononuclear cells, whereas most germinal centre lymphocytes (B cells) were positive for this probe. The number of Ki67 positive cells was greater than histone mRNA bearing cells both in gingiva and tonsillar tissue. In contrast, mantol zone cells (mainly T cells) were sparsely stained by probes of cell proliferation.

CONCLUSION

These results indicate that local proliferation of B cells does not occur in periodontitis gingiva in contrast with tonsillar tissue, although plasma cells showed strong synthetic activity in both tissues. T cells did not appear to proliferate greatly nor undergo active synthesis in either of these tissues. These findings substantiate previous hypotheses that specific leucocytes predominate in the gingival tissue through selective homing rather than by local proliferation.