Thymocyte activating factor(s) in human gingival fluids

Actinobacillus actinomycetemcomitans Y4 capsular polysaccharide induces IL-1beta mRNA expression through the JNK pathway in differentiated THP-1 cells

Capsular polysaccharide from Actinobacillus actinomycetemcomitans Y4 (Y4 CP) induces bone resorption in a mouse organ culture system and osteoclast formation in mouse bone marrow cultures, as reported in previous studies. We also found that Y4 CP inhibits the release of interleukin (IL)-6 and IL-8 from human gingival fibroblast (HGF). Thus Y4 CP induces various responses in localized tissue and leads to the secretion of several cytokines. However, the effects of Y4 CP on human monocytes/macrophages are still unclear. In this study, THP-1 cells, which are a human monocytic cell line, were stimulated with Y4 CP, and we measured gene expression in inflammatory cytokine and signal transduction pathways. IL-1beta and tumour necrosis factor (TNF)-alpha mRNA were induced from Y4 CP-treated THP-1 cells. IL-1beta mRNA expression was increased according to the dose of Y4 CP, and in a time-dependent manner. IL-1beta mRNA expression induced by Y4 CP (100 microg/ml) was approximately 7- to 10-fold greater than that in the control by real-time PCR analysis. Furthermore, neither PD98059, a specific inhibitor of extracellular signal-regulated kinase nor SB203580, a specific inhibitor of p38 kinase prevented the IL-1beta expression induced by Y4 CP. However, JNK Inhibitor II, a specific inhibitor of c-Jun N-terminal kinase (JNK) prevented the IL-1beta mRNA expression induced by Y4 CP in a concentration-dependent manner. These results indicate that Y4 CP-mediated JNK pathways play an important role in the regulation of IL-1beta mRNA. Therefore, Y4 CP-transduced signals for IL-1beta induction in the antibacterial action of macrophages may provide a therapeutic strategy for periodontitis.

Relationship between rheumatoid arthritis and periodontitis

BACKGROUND

Because of several similar features in the pathobiology of periodontitis and rheumatoid arthritis, in a previous study we proposed a possible relationship between the two diseases. Therefore, the aims of this study were to study a population of rheumatoid arthritis patients and determine the extent of their periodontal disease and correlate this with various indicators of rheumatoid arthritis.

METHODS

Sixty-five consecutive patients attending a rheumatology clinic were examined for their levels of periodontitis and rheumatoid arthritis. A control group consisted of age- and gender-matched individuals without rheumatoid arthritis. Specific measures for periodontitis included probing depths, attachment loss, bleeding scores, plaque scores, and radiographic bone loss scores. Measures of rheumatoid arthritis included tender joint analysis, swollen joint analysis, pain index, physician's global assessment on a visual analogue scale, health assessment questionnaire, levels of C-reactive protein, and erythrocyte sedimentation rate. The relationship between periodontal bone loss and rheumatological findings as well as the relationship between bone loss in the rheumatoid arthritis and control groups were analyzed.

RESULTS

No differences were noted for the plaque and bleeding indices between the control and rheumatoid arthritis groups. The rheumatoid arthritis group did, however, have more missing teeth than the control group and a higher percentage of these subjects had deeper pocketing. When the percentage of bone loss was compared with various indicators of rheumatoid arthritis disease activity, it was found that swollen joints, health assessment questionnaire scores, levels of C-reactive protein, and erythrocyte sedimentation rate were the principal parameters which could be associated with periodontal bone loss.

CONCLUSIONS

The results of this study provide further evidence of a significant association between periodontitis and rheumatoid arthritis. This association may be a reflection of a common underlying disregulation of the inflammatory response in these individuals.

Orthodontic tooth movement and de novo synthesis of proinflammatory cytokines

Interleukin-1beta (IL-1beta), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-alpha) are proinflammatory cytokines that are thought to play a role in bone remodeling, bone resorption, and new bone deposition. In the present work, in situ hybridization was performed to measure the messenger RNA expression of IL-1beta, IL-6, and TNF-alpha at 3, 7, and 10 days after the application of orthodontic force on the maxillary first molars of 12 rats. The contralateral side and 3 untreated rats served as controls. Measurements of the messenger RNA expression were selected as the means to investigate the role of orthodontic force in de novo synthesis of proinflammatory cytokines. After the application of force, the induction of IL-1beta and IL-6 was observed to reach a maximum on day 3 and to decline thereafter. No messenger RNA induction of either cytokine was measured in the control teeth. The messenger RNA expression of TNF-alpha was not detected at any time point of this study in the experimental or contralateral sides or in the control animals. Our data support the hypothesis that these proinflammatory cytokines may play important roles in bone resorption after the application of orthodontic force.

Stimulation of prostaglandin E2 and interleukin-1beta production from old rat periodontal ligament cells subjected to mechanical stress

Although the severity of periodontal disease is known to be affected by the age of the host, the pathological role of aging in periodontal disease, especially that attributable to trauma from occlusion, has not been well characterized. Prostaglandin (PG)E2 and interleukin (IL)-1beta are key mediators involved in periodontal diseases, potent stimulators of bone resorption, and are produced by human periodontal ligament (PDL) cells in response to mechanical stress. To investigate age-related changes in the biosynthetic capacity of PGE2 and IL-1beta in PDL cells, we examined the effects of in vivo aging with mechanical tension on PGE2 and IL-1beta expression by rat PDL cells. PDL cells obtained from the incisors of 6-week (young) and 60-week (old) rats were cultured on flexible-bottomed culture plates. The cells were deformed by causing a 9% or 18% increase in surface area at 6 cycles per minute for 1 to 5 days. We found an approximately twofold increase in PGE2 and IL-1beta production by old PDL cells subjected to mechanical tension compared with that by young cells, although the constitutive levels were similar in both. The expression of cyclooxygenase (COX)-2 and IL-1beta mRNA (messenger ribonucleic acid) was enhanced by mechanical tension as determined by use of reverse transcription-polymerase chain reaction (RT-PCR), whereas COX-1 and IL-1beta-converting enzyme mRNA remained unchanged. It is possible that the large amount of PGE2 and IL-1beta produced by PDL cells from an aged host in response to mechanical force may be positively related to the acceleration of alveolar bone resorption.

Comparison of Nd:YAG laser versus scaling and root planing in periodontal therapy

BACKGROUND

The Nd:YAG laser has recently been used in the treatment of periodontal disease. However, although a clinical reduction of probing depth and gingival inflammation to this new approach has been reported, it has not been fully evaluated. Interleukin-1 beta (IL- 1beta), a potent stimulator of bone resorption, has been identified in gingival crevicular fluid (GCF), which is closely associated with periodontal destruction. The aim of this study was to compare the effects of Nd:YAG laser treatment versus scaling/root planing (SRP) treatment on crevicular IL-1beta levels in 52 sampled sites obtained from 8 periodontitis patients.

METHODS

One or 2 periodontitis-affected sites with a 4 to 6 mm probing depth and horizontal bone loss from 3 adjacent single-root teeth in each of 4 separate quadrants were selected from patients for clinical documentation and IL-1beta assay. Sampling site(s) from each diseased quadrant was randomly assigned to one of the following groups: 1) subgingival laser treatment (20 pps, 150 mJ) only; 2) SRP only; 3) laser treatment first, followed by SRP 6 weeks later; or 4) SRP first, followed by laser therapy 6 weeks later. The GCF was collected and the amount of IL-1beta was assayed by enzyme-linked immunosorbent assay (ELISA). Clinical parameters and GCF were measured at baseline and biweekly after therapy for 12 weeks.

RESULTS

An obvious clinical improvement (marked decrease in the number of diseased sites with gingival index > or =2) and reduction of crevicular IL- 1beta were found in all groups. The level of IL- 1beta was significantly lower in the SRP group (P = 0.035) than in the laser therapy group for the duration of the 12 weeks. The laser combined SRP therapy group showed a further reduction of IL- 1beta (6 to 12 weeks after treatment) than either laser therapy alone or SRP combined laser therapy.

CONCLUSIONS

Our data suggest that laser therapy appeared to be less effective than traditional SRP treatment. Of the 4 treatment modalities, inclusion of SRP was found to have a superior IL- 1beta response, when compared to other therapies without it. In addition, no additional benefit was found when laser treatment was used secondary to traditional SRP therapy.

Chemokines are upregulated during orthodontic tooth movement

In the early stage of orthodontic tooth movement, an acute inflammatory response characterized by the migration of leukocytes occurs. This response suggests the presence of specific chemotactic signals that may play a role in the mechanism of bone remodeling, in particular in resorption. The aim of the present study was to explore the induction of potential chemokines at the resorption side during orthodontic tooth movement. Monocyte chemoattractant protein-1 (MCP-1), regulated on activation normal T cell expressed and secreted (RANTES), and macrophage inflammatory protein-2 (MIP-2) were examined by in situ hybridization using radioactive synthetic oligoneucleotide probes. Mesial movement of the upper first molars was performed with a fixed appliance for 3, 7, and 10 days. The results demonstrated that MCP-1, RANTES, and MIP-2 were highly expressed during orthodontic movement. On day 3, MCP-1 showed maximum induction in the pressure zone, followed in intensity by RANTES and MIP-2, although not in the contralateral control side. The induction of these chemokines had declined on day 7 and reached low levels on day 10. Our data suggest that chemokines are induced early in the application of force, and such induction may contribute to the early inflammatory response that may be responsible in part for the ensuing bone remodeling.

Enhancement of lipopolysaccharide-stimulated PGE2 and IL-1beta production in gingival fibroblast cells from old rats

The effect of aging on gingival fibroblasts in response to bacterial infection was studied. Rat gingival fibroblast (rGF) cells were cultured from gingival tissue removed from young (6 weeks old) and old (20 months old) rats. Both types of rGF cells were challenged with lipopolysaccharide (LPS) from the periodontal pathogen Campylobacter rectus. The levels of prostaglandin E2 (PGE2) and interleukin 1beta (IL-1beta) released into the cultured medium were measured by a specific radioimmunoassay. LPS stimulated PGE2 and IL-1beta production in a dose-and time-dependent manner in rGF cells from both young and old rats was seen. Production of PGE2 and IL-1beta by rGF cells from the old rats was higher than those from the young in response to LPS. This greater ability from the older rGF cells to produce PGE2 and IL-1beta was due to higher mRNA levels of cyclooxygenase 2 and IL-1beta, respectively. In contrast, cyclooxygenase-1 and IL-1beta converting enzyme gene mRNA levels remained unchanged. Because LPS-stimulated PGE2 and IL-1beta production was enhanced by in vivo cellular aging, aging of GF may affect the severity of inflammation and bone resorption by producing a large amount of PGE2 and IL-1beta in response to bacterial infection.

Effect of aging on functional changes of periodontal tissue cells

Although the severity of periodontal disease is known to be affected by age, functional changes of periodontal tissue cells during the aging process are not well characterized. It is important to define how cellular aging affects the progression of periodontal diseases associated with the aging process. In vitro aging of human gingival fibroblast (HGF) and periodontal ligament fibroblast (HPLF) cells was prepared by sequential subcultivations (5 to 6 passages as young, 18 to 20 passages as old). GFs were also prepared from gingiva of Down's syndrome patients and 60-week-old rats. Fetal rat calvarial osteoblasts were prepared by sequential digestion with collagenase. HGF and HPLF cells were treated with lipopolysaccharide (LPS) and cyclic tension force, respectively. Amounts of PGE2, interleukin (IL)-1 beta, IL-6, and plasminogen activator (PA) in conditioned media were measured. Total RNA was extracted, and mRNA expression was analyzed by reverse transcription polymerase chain reaction (RT-PCR). LPS-stimulated PGE2, IL-1 beta, IL-6, and PA production was increased in "old" HGF compared to younger cells. According to RT-PCR analysis, gene expression of COX-2, IL-1 beta, IL-6, and tissue type (t) PA was higher in old cells than in young cells. Cyclic tension force to HPLF also stimulated phenotypic and gene expression of IL-1 beta, PGE2 (COX-2 gene) and tPA. These findings suggest that aging in both HGF and HPLF may be an important factor in the severity of periodontal disease through higher production of inflammatory mediators in response to both LPS and mechanical stress. In addition, oxygen radical-treated fibronectin (FN) as substratum diminished bone nodule formation by osteoblasts when compared with intact FN. This finding suggests that FN plays an important role in Osteoblast activity and that FN damaged by oxygen radicals during the aging process may be related to less bone formation.

In vitro cellular aging stimulates interleukin-1 beta production in stretched human periodontal-ligament-derived cells

Although the severity of periodontal disease is known to be affected by host age, the pathological role of aging in periodontal disease, and especially that attributable to trauma from occlusion, has not been well-characterized. Interleukin (IL)-1 beta is a key mediator involved in periodontal diseases, a potent stimulator of bone resorption. Furthermore, it is produced by human periodontal ligament (PDL) cells in response to mechanical stress. To investigate the age-related changes in the biosynthetic capacity of IL-1 beta in PDL cells, we examined the effects of in vitro cellular aging with mechanical stress on IL-1 beta protein and gene expression by human PDL cells. Human PDL cells (young = 5th or 6th passage; old = 18-20th passage) were cultured on flexible-bottomed culture plates, and the cells were deformed at 6 cycles per min at 2 steps of tension force for 1 to 5 days. We found a two-fold increase in IL-1 beta production by old PDL cells subjected to mechanical tension compared with that by young PDL cells, although the constitutive levels of IL-1 beta were similar in both the young and old PDL cells. This increase was tension-dependent. IL- 1 beta mRNA was also detected in both cell types under basal conditions, and its expression was further enhanced by application of mechanical tension by use of reverse-transcription-polymerase chain-reaction (RT-PCR) and in situ hybridization methods. The increase in signal rate was higher in the old cells than in the young cells. IL-1 beta-converting enzyme mRNA remained unchanged. It is possible that a large amount of IL- 1 beta produced by PDL cells from an aged host in response to mechanical force may be positively related to the acceleration of alveolar bone resorption.

Factors affecting IL-1-mediated collagen metabolism by fibroblasts and the pathogenesis of periodontal disease: a review of the literature

Fibroblasts have been studied extensively for their contribution to connective tissue destruction in diseases where the metabolism of extracellular matrix components plays an essential part in their pathogenesis. A considerable dissolution, especially of collagen fibrils, is a well-known characteristic of the periodontal ligament and the gingival connective tissue in microbial-induced periodontal disease. Fibroblasts, responsible for the assembly of the extracellular matrix, are capable of responding directly to oral microbial challenges or indirectly, following activation of the host immune response, and can alter the composition of connective tissue in several ways: synthesis of inflammatory mediators, their receptors and antagonists; fibroblast proliferation; collagen synthesis; phagocytosis of collagen fibrils; and synthesis of proteolytic enzymes, including matrix metalloproteinases and their corresponding inhibitors. The contributions of these cellular fibroblastic properties to the pathogenesis of periodontal disease are reviewed in the context of the cytokine, interleukin-1, as the inflammatory regulator.

Interleukin-1 beta, prostaglandin E2, and immunoglobulin G subclasses in gingival crevicular fluid in patients undergoing periodontal therapy

Determination of the presence of inflammatory products found in gingival crevicular fluid (GCF) may be of value in evaluating both periodontal disease status and the outcome of therapy. Immunoglobulin G subclasses 1 through 4 (IgGs), interleukin 1-beta (IL-1 beta), and prostaglandin E2 (PGE2) have all been shown to be present in GCF. This study monitored IgGs, IL-1 beta, and PGE2 in GCF of 18 adult patients as they progressed through periodontal treatment toward maintenance therapy. Sites were selected from the most severely affected sextant as determined by probeable crevice depth (PD) at initial examination (IE). GCF was collected on four occasions: initial examination; 4 weeks after completion of initial therapy (oral hygiene counseling, and scaling and root planing); 3 months after completion of surgery; and 7 to 9 months later at a maintenance visit. All variables were reduced to binary form (positive or negative), and break points chosen to separate the approximately symmetrical bell-shaped areas (negatives) from the skewed tails (positives). Repeated measures analyses of variance were performed to detect significant changes in all variables across time. Significant improvements were observed for all the clinical variables measured: PD, attachment level, and bleeding on probing. However, significant reductions for the GCF components only occurred in the concentrations of IL-1 beta and PGE2, but were not evident until the maintenance sampling. Surprisingly, GCF:serum ratios of IgG subclasses did not change significantly over the course of the investigation. The robustness of the levels of these components may be due to inflammation associated with the healing process, or to a further plaque induced response.

Production of interleukin-1 by polymorphonuclear leukocytes resident in periradicular tissue

Twenty-one patients undergoing endodontic surgery were identified. Periradicular tissue samples were recovered, and those showing significant numbers of polymorphonuclear leukocyte (PMN) infiltration were prepared for immunoperoxidase identification of interleukin (IL)-1 alpha and IL-1 beta-producing cells using specific polyclonal antibodies. In selected tissue specimens, 90% or more of the PMN's were found to stain positively for IL-1 alpha and IL-1 beta. In addition, significant numbers of plasma cells and tissue histiocytes stained positively for these IL's. Cell suspensions from selected periapical granuloma specimens, as well as from purified peripheral blood PMN's and peripheral blood mononuclear cells, were also subjected to IL-1 quantitation using a commercial ELISA procedure. Such cell suspensions were found to produce significant levels of IL and could be stimulated to produce increased levels after coculture with lipopolysaccharide. These results suggest that PMN's in inflammatory periradicular tissues may be a significant source of IL-1, and their possible roles in the establishment and resolution of periradicular lesions need to be re-evaluated.

Collagenases and tissue inhibitors of metalloproteinases: a functional balance in tissue degradation

BACKGROUND

Members of the family of matrix metalloproteinases (MMPs; also called collagenases or matrixins) are key enzymes in matrix degradation. They function at neutral pH and can digest synergistically all the matrix macromolecules. Biochemical and clonal studies indicate that there are three major groups: the specific collagenases cleave interstitial collagens; the gelatinases degrade types IV, V, VII and XI collagens and act synergistically with collagenases by degrading denatured collagens (gelatins); and the stromelysins have broader specificity and can degrade basement membrane collagens as well as proteoglycans and matrix glycoproteins. Others not in these groups are matrilysin, metalloelastase and a recently cloned membrane-bound metalloproteinase. MMPs are Zn(2+)- and Ca(2+)-requiring endopeptidases and are secreted in a latent proform: activation involves the loss of a propeptide. Naturally occurring inhibitors, TIMPs (Tissue Inhibitors of MetalloProteinases), are important controlling factors in the actions of MMPs, and tissue destruction in disease processes often correlates with an imbalance of MMPs over TIMPs. The major inhibitor is TIMP-1 (or TIMP), a 30-kDa glycoprotein that is synthesised by most cells. A second unglycosylated inhibitor, TIMP-2, which is less abundant, has the interesting property of binding to the proform of gelatinase A and is involved in controlling its activation.

BIOLOGICAL AND PSYCHOLOGICAL IMPLICATIONS

The expression of MMPs and TIMPs by cells is regulated by many cytokines (particularly interleukin-1, IL-1), growth factors and hormones, some of which are specific to cell type and others that are ubiquitous (eg transforming growth factor beta, TGF-beta). Many of these factors are products of monocytes/macrophages and their production in inflammatory situations is therefore part of the chain of events leading to tissue degradation. From many recent studies it seems that tissue destruction, both physiological and pathological, is correlated with an imbalance of inhibitors over proteinases. We proposed that one way in which pathogenic organisms might mediate tissue degradation in periodontal diseases is through the ability of cell wall antigens to stimulate cytokine production by circulating mononuclear cells. These would then induce MMP synthesis by resident gingival cells (or by the mononuclear cells themselves), thereby initiating degradative events. We have identified MMPs in human gingival biopsy specimens by using specific polyclonal antibodies and indirect immunofluorescence. Their distributions are extremely variable, both in the connective tissue and the epithelium, but the results indicate that host cell production of MMPs may contribute to tissue degradation in periodontal disease. TIMP could also be found in some situations and could be a limiting factor.

Crevicular interleukin-1 beta in moderate and severe periodontitis patients and the effect of phase I periodontal treatment

Interleukin-1 beta (IL-1 beta), a potent stimulator of bone resorption, has been implicated in the pathogenesis of periodontal destruction. However, the relationship between cytokines and periodontal disease has not been studied sufficiently to allow definitive conclusions. The aims of this study are to investigate crevicular IL-1 beta and the clinical status of patients with periodontitis and the effect of phase I periodontal therapy on levels of IL-1 beta. For this study, 130 gingival crevicular fluid (GCF) samples were harvested from non-inflamed (15) and diseased sites (115) in 11 patients with periodontitis. The gingival index (GI) and probing depth (PD) of each site was recorded initially and one month after treatment. The amount of IL-1 beta in the GCF was measured by enzyme-linked immunosorbent assay (ELISA) using an antibody specific for this cytokine. Before treatment, IL-1 beta was found in 12 of 15 non-inflamed gingival crevices and in 112 of 115 diseased pockets. The amount of IL-1 beta varied from 4.03 to 511.12 pg/site. The average amount of IL-1 beta from diseased sites was 3-fold greater than that from non-inflamed sites. Both total amount of IL-1 beta and the GCF volume, but not IL-1 beta concentration, were found to be correlated, positively, with GI score and PD. After therapy, 63 sites from 7 patients were re-examined, and the amount of IL-1 beta in 49 of 63 sites was found to have declined. These data suggest that the amount of crevicular IL-1 beta is closely associated with periodontal status. This relationship may be valuable in monitoring periodontal disease activity.

Bacterial-stimulated cytokine production of peripheral mononuclear cells from patients of various periodontitis categories

Periodontitis is a general term for disease categories, including juvenile periodontitis (JP), rapidly progressive periodontitis (RPP), and adult periodontitis (AP), which may or may not share a common etiology and pathogenesis. These disease categories are characterized by differences in progression of tissue destruction and differences in age group susceptibility, but not, to our knowledge, by differences in cytokine responses of inflammatory cells. The present study examined blood cell counts and interindividual variation in the ability of PBMC of patients in three different categories of periodontitis to produce cytokines after stimulation with different oral bacterial species in vitro. The AP group had a significantly lower production of IL-1ra when stimulated with Porphyromonas gingivalis (P.g.) and Actinobacillus actinomycetemcomitans (A.a.) (P < 0.05). Streptococcus sanguis (S.s.), which is associated with normal periodontal conditions, induced extremely high levels of IL-1 alpha and TNF alpha production in all groups. The RPP group had a significantly higher number of monocytes (MC) than the AP group (P < 0.05). Additionally, JP patients had a significantly higher concentration of polymorphonuclear granulocytes compared to juvenile controls (P < 0.05). In conclusion, IL-1 alpha, TNF alpha, or IL-6 production by peripheral blood MC after in vitro stimulation with oral bacterial type stains may not distinguish different categories of periodontitis. The results support the hypothesis that the cytokine IL-1ra is produced in different concentrations in the two groups: RPP and AP. Furthermore, elevated MC concentration in the RPP group compared to the AP group may be an important pathogenic feature in RPP.

IL-4- and IL-6-producing cells in human periodontal disease tissue

IL-4- and IL-6-producing cells in human periodontal disease tissues were investigated using immunohistochemical and in situ hybridization techniques. Immunohistochemical analysis demonstrated the presence of IL-4-producing cells within the CD45RO+ subset and the percentage of IL-4+ cells was significantly higher in periodontal lesions than in gingivitis tissues (p < 0.01). The percentage of IL-6-producing memory cells was higher in periodontal lesions compared with gingivitis tissues, although it was not statistically significant (p > 0.05). A reverse tendency in IL-4- and IL-6-positive cells was observed in a few individual cases. No IL-4 mRNA could be detected using the in situ hybridization technique. However, high levels of IL-6 mRNA were present in clinically healthy tissues, with a further increase in both epithelium and connective tissues affected by gingivitis, although only the former was significant (p < 0.025). There was a significant decrease in IL-6 mRNA in both the connective tissue (p < 0.025) and epithelium (p < 0.01) in periodontitis tissues compared with levels in gingivitis tissues. However, the levels of IL-6 mRNA in periodontal tissues were high compared with those of IL-1 mRNA, which was used in this study as a positive control. These results suggest that Th2-type cells may accumulate in periodontal lesions.

Connective tissue degradation in health and periodontal disease and the roles of matrix metalloproteinases and their natural inhibitors

Connective tissue remodeling is essential for normal growth and development, and many diseases have long been associated with the breakdown of the collagenous matrix of bone, cartilage, and related tissues. Recent work has established that members of the family of matrix metalloproteinases (MMPs) are key enzymes in matrix degradation. They function at neutral pH and can digest synergistically all the matrix macromolecules. Biochemical and cloning studies indicate that there are three major groups, collagenases, gelatinases, and stromelysins. Naturally occurring inhibitors, TIMPs (Tissue Inhibitors of MetalloProteinases), are important controlling factors in the actions of MMPs, and tissue destruction in disease processes often correlates with an imbalance of MMPs over TIMPs. The major inhibitor is TIMP-1 (or TIMP), a 30-kDa glycoprotein that is synthesized by most cells. The expression of MMPs and TIMPs by cells is regulated by many cytokines (particularly interleukin-1, IL-1), growth factors, and hormones, some of which are specific to cell type and others that are ubiquitous (e.g., transforming growth factor beta, TGF-beta). One way in which pathogenic organisms might mediate tissue degradation in periodontal diseases is through the ability of cell wall antigens to stimulate cytokine production by circulating mononuclear cells. These would then induce MMP synthesis by resident gingival cells, thereby initiating degradative events. Direct in vivo evidence for the source of collagenase and other MMPs in periodontal tissues is limited. By using specific polyclonal antibodies and indirect immunofluorescence, we could demonstrate the presence of collagenase, stromelysin-1, gelatinase A, and TIMP in human gingival biopsy specimens.(ABSTRACT TRUNCATED AT 250 WORDS)

Interleukin-1 beta concentration of gingival crevicular fluid

The concentration of interleukin-1 beta is elevated in inflamed gingival tissue. Therefore a method for the measurement of interleukin-1 beta (Il-1 beta) in gingival crevicular fluid (GCF) using a commercially available Il-1 beta ELISA was developed. GCF was collected with periopaper strips and 4 protocols of sampling using filter paper strips were tested; the method with a recovery rate of 111.9% (SD: +/- 14.5%) was chosen for subsequent analysis of all samples. Il-1 beta concentration in GCF of periodontitis patients and a healthy control group was determined. Patients (n = 19, mean age: 29.3 years) had not been treated. The healthy control group (n = 14, mean age: 22.8 years) showed, after a hygiene regimen of 2 weeks, no clinical signs of gingival/periodontal inflammation. Probing depth, clinical attachment level, bleeding upon probing, and a modified plaque index were recorded. Il-1 beta could be detected in all GCF samples. The concentration ranged between 22.8 ng/ml and 150 ng/ml in the healthy control group and between 85.8 ng/ml and 882.2 ng/ml in the periodontitis patients. No sex-related differences were noted. According to our present results the determination of GCF Il-1 beta concentration is possible using commercially available test kits if the principle of sample preparation is adapted to the specific requirements of GCF analysis.

Marginal periodontitis and cytokines: a review of the literature

Recent research on the immunopathogenesis of marginal periodontitis has focused on cytokines, because these mediators govern biological activities in inflammatory tissue destruction. Several studies have been carried out to elucidate the involvement of cytokines in periodontitis, including cytokine measurements in samples from gingival tissue, gingival crevicular fluid, and in supernatants of stimulated in vitro grown cells from gingival tissue and peripheral blood. The results, summarized in this review, suggest that cytokines are involved in the progress of periodontitis. Furthermore, cytokines may be valuable as markers of tissue breakdown. At the present stage, however, there are difficulties in detecting and quantifying cytokines by immunochemical methods and, in particular, by bioassays. Increased knowledge of the cytokine network may open new pathways of periodontitis treatment by controlling processes involved in tissue breakdown.

Measurements of interleukin-6 in gingival crevicular fluid from adults with destructive periodontal disease

This paper describes a study of whether or not the amounts of interleukin-6 (IL-6) in gingival crevicular fluid (GCF) are correlated with periodontal clinical measures. A sensitive ELISA was developed to measure IL-6 in GCF. Two male and 3 female adult subjects with periodontal disease were examined at their first appointments, after 3 months, and after 6 months. Data were obtained on plaque index (PI), bleeding index (BI), probing depth (PD), and on the IL-6 content of GCF samples from 16 sites per subject for a total of 240 measurements. Significant correlations were found between BI and IL-6 (P < 0.005) and between PD and IL-6 (P < 0.05), but not between PI and IL-6. Only 6 out of the 80 sites (in 3 of the 5 subjects) showed PD increases of at least 2 mm. However, for each of these 3 subjects, the amounts of IL-6 in the GCF samples from these sites were markedly higher than the mean amounts of IL-6 in the GCF samples from the remaining sites. These findings suggest that IL-6 may be a useful indicator of periodontal disease, although more extensive longitudinal studies are needed to determine the real clinical value of this GCF component.

IL-1 in gingival crevicular fluid following closed root planing and papillary flap debridement

Interleukin (IL)-1 alpha and beta are cytokines which can mediate inflammatory, bone resorbing, and reparative effects in the periodontium, but few longitudinal data exist exploring their role following periodontal therapy. This study examined gingival crevicular fluid (GCF) concentrations of IL-1 alpha and IL-1 beta at sites with shallow sulci (SS) or inflamed moderate/advanced pockets (M/AP) before and 6 months after treatment with closed scaling/root planing (SC/RP) or papillary flap debridement (PFD), all in the same subject (n = 14 patients). No significant differences were noted in IL-1 alpha or beta concentrations (determined with two-site enzyme-linked immunosorbent assays) between SS and M/AP sites at baseline. While both therapies improved clinical parameters of periodontal disease, IL-1 alpha concentration increased significantly (p < 0.05) in M/AP-PFD sites 6 months after treatment, but were unchanged in other groups. IL-1 beta concentrations were numerically lower after therapy, except for a significant increase (p < 0.05) in M/AP-PFD sites. These data suggest that surgical wound healing in an inflamed, plaque-infected site (M/AP-PFD) results in prolonged production of IL-1, which may be a reflection of the extent of tissue trauma and delayed wound healing. In spite of increased IL-1 levels, these sites demonstrated significant short-term improvement in clinical attachment level (+ 1.8 mm, p < or = 0.001) postoperatively.

Gingival fluid IL-1 and IL-6 levels in refractory periodontitis

Selected gingival bacteria and cytokine profiles associated with patients who did not respond to conventional periodontal therapy (refractory) were evaluated. 10 subjects with a high incidence of post-active treatment clinical attachment loss (> 2% sites/year lost > or = 3 mm) were compared to 10 age-, race-, and supragingival plaque-matched patients with low post-treatment clinical attachment loss (< 0.5% sites/year) relative to the following parameters at 2 sites/patient with the deepest probing depths: (1) presence of 3 selected periodontal pathogens (Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Eikenella corrodens) in subgingival plaque as determined by selective culturing, and (2) gingival crevicular fluid (GCF) levels of 3 cytokines associated with bone resorption (IL-1 alpha, IL-1 beta, IL-6) as determined by two-site ELISA. Results indicated no significant differences in any clinical measurement (except incidence of clinical attachment loss), in the presence of any bacterial pathogen, or in GCF cytokine levels between refractory subject sites versus stable subject sites. However, when sites producing the greatest total GCF cytokine/patient were compared, sites from refractory patient produced significantly more IL-6 (30.1 +/- 4.0 versus 15.4 +/- 2.8 nM, p < 0.01). The subgingival presence of each of the 3 bacterial pathogens was associated with elevated GCF IL-1 concentrations. These data suggest that gingival IL-1 and IL-6 production is different in response to local and systemic factors associated with periodontitis, and that IL-6 may play a role in the identification and mechanisms of refractory periodontitis.

Localization of interleukin-1 (IL-1) mRNA-expressing macrophages in human inflamed gingiva and IL-1 activity in gingival crevicular fluid

The exact cell type and site(s) involved in interleukin-1 (IL-1) production during gingival inflammation was determined by combining immunohistochemistry and in situ hybridization. IL-1 messenger RNA (mRNA)-expressing cells in human inflamed gingiva were identified as macrophages. The rate of IL-alpha mRNA expression in these macrophages was the same as IL-1 beta mRNA expression. The rate of IL-1 mRNA expression was higher in connective tissue furthest from the pocket epithelium, although more macrophages were present at the connective tissue subjacent to the pocket epithelium. The IL-1 activity in gingival crevicular fluid (GCF) obtained from inflamed gingiva was higher than that from healthy gingiva and decreased after periodontal therapy. The IL-1 activity in GCF was almost completely abolished by the addition of anti-IL-1 alpha antibody but not by anti-IL-1 beta antibody, indicating that IL-1 alpha is the predominant form in GCF. However, the IL-1 activity in GCF was unrelated to the number of IL-1 mRNA-expressing macrophages in the same gingival site where the GCF was obtained at the same time. The results suggest that macrophages in the connective tissue subjacent to the oral epithelium contribute to the production of IL-1 but those in connective tissue subjacent to the pocket epithelium play a different role in the generation of gingival inflammation.

Host responses in periodontal diseases: current concepts

In periodontal diseases, bacteria trigger inflammatory host responses which, along with the direct destructive effects of the bacteria, cause most of the tissue destruction. Periodontal inflammatory responses are, by and large, immunologic, and our understanding of these reactions has been advanced by the explosion of knowledge in immunobiology, some of which is discussed in this review. Understanding the role of immune cells and their regulatory cell surface molecules such as the MHC, CD antigens, and receptors, as well as knowledge of effector systems set into motion such as phagocytes and cytotoxic T-cells, and the effector molecules such as antibodies, complement, and cytokines, have led to better understanding of the complex pathogenesis of periodontal disease. The role of mediators including the matrix metalloproteinases, proteoglycans, the kinins and anaphylatoxins, and low molecular weight mediators including products of arachidonic metabolism is beginning to be elucidated in periodontal disease. Important avenues of research for development of diagnostic tests based upon host response are apparent. For example, tissue products released during periodontal inflammation including the metalloproteinases, elastase, cytokines, prostaglandins, antibodies, and complement components may provide the basis for future diagnostic indicator tests. The recognition that the neutrophil/antibody/complement axis is critical for protection against periodontal bacteria and that abnormalities in this system often lead to increased periodontal susceptibility provide approaches for the development of diagnostic tests assessing risk. A group of factors which are negative regulators of inflammation including TGF-beta, gamma-interferon, and IL-1 receptor antagonist provide potential for assessment of periodontal disease in remission or in the healing phase. Finally, factors such as HLA associations and the molecular basis for neutrophil abnormalities may provide genetic markers for periodontal disease susceptibility. Diagnostic factors based upon host response measures offer great potential for predicting host susceptibility and will likely be used in combination with microbial diagnostics which identify specific infecting organisms.

Host mediators in gingival crevicular fluid: implications for the pathogenesis of periodontal disease

During the past few years, a considerable number of studies have examined different aspects of the host response in gingival crevicular fluid (GCF), including the relationship of specific markers to the active phases of periodontal disease. Various indicators of the acute inflammatory response (the lysosomal enzymes beta-glucuronidase and collagenase, the cytoplasmic enzyme aspartate aminotransferase, and the arachidonic acid metabolite PGE2) have been shown to be associated with clinical attachment loss in chronic adult periodontitis in man and experimental periodontitis in animal models. In contrast, the relationship of indicators of the humoral immune response in GCF to active periodontal disease is equivocal. Furthermore, a number of indicators of the cellular immune response have been identified recently in GCF (i.e., Interleukin-1 alpha, IL-1 beta, tumor necrosis factor-alpha), but their relationship to active phases of periodontal disease have not been studied. The polymorphonuclear leukocyte (PMN) is the cellular hallmark of acute inflammation. Evidence from the GCF studies suggests that hyperreactivity of these cells plays a critical role in the active phases of some forms of periodontal disease. Metabolic activation of PMN can be associated with a number of potentially destructive reactions. The major effector mechanism for tissue destruction that can be specifically identified with the PMN is the synergistic effect of the release of PMN proteases and the generation of reactive oxygen metabolites by these cells. Priming of the PMN, where the PMN response is enhanced by agents that do not initiate the response, may be an important mechanism for PMN activation in the crevicular environment; for example, cytokines such as IL-1 beta and TNF-alpha, and lipopolysaccharides released from subgingival Gram-negative bacteria, can serve this function. The hypothesis proposed here argues that in addition to the severe forms of periodontal disease that have been associated with qualitative or quantitative PMN defects, tissue destruction in the periodontum can be observed with hyperreactivity of these cells. These differing conclusions do not create a dilemma, but may represent opposite ends of a balance that is no longer in equilibrium.

Interleukin-6 production by human gingival fibroblasts

The ability of human gingival fibroblasts to synthesize interleukin-6 (IL-6) was studied using in vitro and immunohistochemical techniques. Culture supernatants of human gingival fibroblasts contained significant quantities of IL-6 activity which could be stimulated by fetal calf serum, recombinant interleukin-1 beta and lipopolysaccharide. The activity in the supernatants was specifically attributed to IL-6 since up to 97% of the activity could be inhibited by an anti-IL-6 antibody. Immunohistochemical studies on low-density human gingival fibroblast cultures indicated that the cells were associated with material reactive to the anti-IL-6 antibody. This localization was seen on the cell surface and in the cytoplasm of the cells. Immunoreactivity towards IL-6 was also noted in sections of human gingivae. Moderate staining was seen in the connective tissues and lower portions of the gingival epithelium, while intense staining was seen at foci of inflammation. The identification of IL-6 with human gingival tissues and cells implicates this lymphokine in the molecular events associated with the inflammatory periodontal diseases.

Acute-phase protein detection and quantification in gingival crevicular fluid by direct and indirect immunodot

The development of an assay for markers of active periodontitis, obtained directly from gingival crevicular fluid (GCF) and simply quantified, would be of great importance to the dental practitioner. The purpose of this study was to evaluate direct and indirect immunodot techniques as to their potential in easily quantifying acute-phase proteins within periodontally diseased and healthy site GCF. Indirect immunodots (GCF eluates dotted onto nitrocellulose membrane) using monoclonal antibodies and a radioactive isotope label were used to identify and establish relative amounts of C-reactive protein (CRP) and alpha-2-macroglobulin (A2M) in 2 diseased and 2 healthy sites in 24 periodontitis patients. Periodontally diseased sites were found to contain significantly lower concentrations of A2M than healthy sites (p less than 0.001), but CRP levels did not vary significantly between healthy and diseased locations. Using a direct immunodot assay (GCF absorbed directly into nitrocellulose membrane strips), A2M levels quantified with radioactive isotopes at healthy and diseased sites could be correlated with A2M levels determined by enzyme-linked antibody-colormetric probes at those same sites. Such a direct sampling and quantification system shows promise for future "in-office" diagnostic methodology.

Divergent effect of the anaerobic bacteria by-product butyric acid on the immune response: suppression of T-lymphocyte proliferation and stimulation of interleukin-1 beta production

The effects of short-chain fatty acids (SCFA) produced by anaerobic bacteria, namely propionic, butyric and iso-butyric on T-cell proliferation was investigated. A dose-dependent inhibition of both phytohemagglutinin-induced blastogenesis and mixed lymphocyte culture was observed in the millimolar range of SCFA concentrations. The tested SCFA displayed different levels of suppression. The degree of activity was in the following order: butyrate greater than propionate greater than isobutyrate. T-cell inhibition was partially reversed, at least for propionic and isobutyric acids, by increasing the concentration of macrophages in the assay system. Furthermore, butyric acid displayed an interesting biphasic stimulation of monocyte interleukin-1 beta production, a cytokine with a powerful bone-resorbing activity. Since millimolar concentrations of SCFA are present in gingival fluid from periodontal pockets, the observed results support the role of these by-products of anaerobic metabolism in the pathogenesis of periodontal diseases.

Cytotoxic and immunostimulatory effects of Bacteroides cell products

The etiologic role of Bacteroides in both periodontal and periapical infections has been well documented, with current interest focusing on the specific pathogenic mechanisms involved. The effects of cell fractions derived from Bacteroides gingivalis (BG), Bacteroides intermedius (BI), and Bacteroides asaccharolyticus (BA) have been studied in vitro through: an assessment of the direct cytotoxic effects on human gingival fibroblasts using a tetrazolium dye reduction assay, an evaluation of murine lymphocyte stimulation and interleukin-1 release, and the induction of human lymphocyte-mediated cytotoxicity. Both BG and BI stimulated interleukin-1 release (P less than 0.001), while BA, a nonoral organism, was not significantly active in this respect. Only BG sonicates were able to induce lymphocyte-mediated cytotoxicity (P less than 0.005). All three Bacteroides species demonstrated direct cytotoxic effects on cultured gingival fibroblasts, and these effects were related to the relative protein content and endotoxin activity of the sonicate preparations for each organism. These data show that BG and BI possess factors which may enhance their virulence through activities not shared with BA.

The release of interleukin-1 beta, tumor necrosis factor-alpha and interferon-gamma by cultured peripheral blood mononuclear cells from patients with periodontitis

The extracellular release of IL-1 beta by cultured peripheral blood monocytes from 26 periodontitis patients and 26 control subjects was measured by radioimmunoassay. Unstimulated monocytes from periodontitis patients released significantly more IL-1 beta than controls during 24 h of culture; there was a wide variation in the amount of IL-1 beta released (0.45-13.00 ng/ml per 10(6) cells) which did not correlate with either the degree of bone loss or pocket formation observed clinically. When stimulated with lipopolysaccharide (LPS; Actinobacillus actinomycetemcomitans; 5 micrograms/ml) monocytes from periodontitis patients produced significantly more IL-1 beta than those from control subjects. Monocyte culture supernatants from another 10 periodontitis patients and 10 control subjects were also assayed for both IL-1 beta and TNF-alpha by enzyme-linked immunosorbent assays. Spontaneous and LPS-stimulated (Bacteroides gingivalis; 5 micrograms/ml) IL-1 beta release were again significantly higher for periodontitis patients. TNF-alpha was detected in the periodontitis cultures (0-765 pg/ml per 10(6) cells), but the mean value was not significantly different from controls. LPS-stimulated TNF-alpha release, however, was significantly higher than for control subjects, and there was a strong correlation between spontaneous IL-1 beta and TNF-alpha release by monocytes from the periodontitis group. Measurement of interferon-gamma (IFN-gamma) in lymphocyte cultures from these patients by immunoradiometric assay showed that IFN-gamma levels in periodontitis cultures were consistently low, but not significantly so when compared to controls; both groups responded equally to concanavalin-A (5 micrograms/ml). Although the precise roles of IL-1 beta and TNF-alpha in periodontitis remain unclear, these data provide evidence that both cytokines may participate in the pathogenesis of the disease.

Within-mouth correlations for indicators of the host response in gingival crevicular fluid

Gingival crevicular fluid was collected from multiple sites in patients with chronic adult periodontitis, and analysed for the lysosomal enzymes beta-glucuronidase and arylsulphatase, the cytoplasmic enzyme lactate dehydrogenase, total IgA, IgG and IgM and the protease inhibitor alpha 2-macroglobulin. The within-mouth (intraclass) correlation coefficients were calculated to describe the relationship between samples collected from individual patients. Data collected at baseline and 3 months after root planing and scaling were analysed, as was the change between examinations. Volume of crevicular fluid demonstrated the smallest intraclass correlation coefficient (0.16 at baseline, 0.12 at 3 months; 0.11 change), while probing depth and enzyme activity had moderate intraclass correlations (i.e. 0.36, 0.36, 0.26 for beta-glucuronidase). Immunoglobulin and alpha 2-macroglobulin activity in the fluid had the strongest correlations (i.e. 0.64, 0.57, 0.65 for IgG). The correlations for anatomically related teeth within a quadrant (molar, non-molar) were equivalent to or greater than the correlation for all samples within a mouth. Examined by tooth type, the intraclass correlations for volume of crevicular fluid, probing depth, beta-glucuronidase, arylsulphatase and lactate dehydrogenase were higher for non-molar teeth. In contrast, intraclass correlations for IgA, IgG, IgM and alpha 2-macroglobulin in samples from molar teeth were either equivalent to or greater than the correlations for non-molar samples. Calculation of intraclass correlation coefficients for such data can (1) indicate the degree of variability present in multiple samples of crevicular fluid collected from individual patients, (2) provide information about the source of host mediators in the fluid, and (3) help identify appropriate sampling strategies for the fluid.

Increased interleukin-1 beta (IL-1 beta) concentration in gingival tissue from periodontitis patients

Human gingival tissues from periodontitis patients were found to contain from 126 fg/mg to 2161 fg/mg interleukin-1 beta as determined by a sensitive enzyme linked immunoassay. No IL-1 beta could be found in normal gingival tissue. This finding may have important consequences relevant to connective tissue destruction and episodes of alveolar bone resorption characteristic of chronic periodontitis.

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.

Immunoregulatory aspects of periodontal disease

This manuscript reviews our studies of the composition and functional capabilities of gingival tissue lymphocytes from patients with periodontal disease. The emphasis has been on phenotyping the local lymphoid infiltration in gingival and periodontal disease. The preparation and phenotypic analyses of cells recovered from diseased and healthy human periodontal tissues indicated that T-cell subset ratios from diseased tissue were significantly decreased compared with peripheral blood or normal tissue ratios. These reductions were verified in a second study we performed using two-color immunofluorescence analyzed by flow cytofluorometry. Local variations in the CD4 + cell population were also found in diseased tissue cells when these were compared with normal tissue cells. The relative percentage of CD4+ cells labeled with anti-helper inducer (4B4) or anti-suppressor inducer (2H4) monoclonal antibodies was increased above that of normal tissue cells. Functional studies of immunoglobulin production by gingival cells from adult periodontitis tissues showed two discrete patterns of synthesis and also suppression of immunoglobulin synthesis after addition of mitogen to the cultures. Removal of macrophages also drastically reduced immunoglobulin synthesis by gingival cells. These results indicate that there is an abundance of suppressor T-cells in diseased tissue and that functional suppression is demonstrated by lymphocytes from periodontal disease tissue. The findings of these investigations have suggested potentially important roles for immune regulation in periodontal disease.

Specialized postcapillary venules in human gingival tissue

High endothelial venules (HEV) are specialized postcapillary venules that play a central role in lymphocyte migration and recirculation. This study examined the occurrence and morphology of HEV-like vessels in healthy gingiva and in lesions of chronic gingivitis in children, experimental gingivitis in adults, adult periodontitis, and in periapical granulomas. HEV-like vessels were absent in gingival health, but present during the development of inflammation and in chronic inflammation. The morphology of these HEV-like vessels in the oral cavity resembled that of lymphoid HEV. Thus gingival HEV may represent sites for the entry of lymphocytes into chronic inflammatory lesions.

The regulation of Langerhans cell T6, DR and DQ antigen expression: an hypothesis

A hypothetical model of the maturation pathway of Langerhans cells (LC) within an epithelial environment is presented. This model is based on in vitro studies using human gingival organ culture. In this model, T6 (CD1) antigen is induced on a T6(-) intraepithelial population by Interleukin-1 secreted by epithelial cells. This process is abrogated by a locally produced Interleukin-1 inhibitor, ILS. These T6(+) LC then express first HLA-DR and subsequently HLA-DQ surface antigens under the influence of either lipopolysaccharide or gamma interferon. The induction of these Class II antigens on LC is inhibited by prostaglandin E2. It is postulated that these Class II antigen positive LC are then available to function as antigen presenting cells. This hypothesis is consistent with in vitro studies and several in vivo observations. The basis of the hypothesis is the demonstration that locally produced factors may exert an influence on LC behaviour within an epithelial environment.

Possible mechanisms involved in the immunoregulation of chronic inflammatory periodontal disease

It is generally agreed that immunological mechanisms are involved in the pathogenesis of periodontal disease; however, regulation of these mechanisms has hitherto received scant attention. Regulatory networks exist at both a cellular and a molecular level. At the cellular level, the existence of helper (T4-positive) and suppressor (T8-positive) T lymphocytes, the expression of Class II major histocompatibility complex antigens, and the heterogeneity of macrophage subpopulations are central to an understanding of the regulatory mechanisms involved. It is only recently that studies of these separate components, in both humans and experimental animals, have begun to provide a basis for understanding the complex interactions occurring in periodontal disease. Studies using the human experimental gingivitis model have shown an immunoregulatory picture consistent with a controlled immunological reaction with an essentially normal T4:T8 ratio of 2.0. In contrast, studies utilizing cells extracted from adult periodontitis lesions have shown a reduced T4:T8 ratio (approximately 1.0) and an inability to respond in, or to stimulate, an autologous mixed lymphocyte reaction. Animal studies using athymic nude rats have supported the concept of a central role for T-cell control in periodontal disease and the possibility of an imbalance in this control with disease progression. These results are reviewed and areas of future research explored.

1985 Kreshover lecture. Molecular factors influencing neutrophil defects in periodontal disease

Major advances in our understanding of the role of the neutrophil in host defense against periodontal organisms have been made through studies of localized juvenile periodontitis (LJP). Several lines of evidence suggest that LJP is an infectious process closely associated with Actinobacillus (Haemophilus) actinomycetemomitans as a causative agent, although other organisms may also participate. The immunologic profile of LJP patients suggests that a cell-associated neutrophil locomotory dysfunction is a key underlying immunodeficiency resulting in increased susceptibility to periodontal infection. In addition, LJP patients often exhibit cervical lymphadenopathy and IgG-hypergammaglobulinemia, and a markedly elevated antibody response to the infecting organism, A. actinomycetemcomitans, is found in the serum and crevicular fluid of most patients. Evaluation of the locomotory properties of LJP neutrophils shows that random migration and chemokinesis are normal; however, about 70% of the LJP patients suffer from a defect in chemotaxis, with their neutrophils responding poorly to bacterial chemotactic factors, synthetic chemotactic peptides, and complement fragments (C5a). Depressed chemotaxis of LJP neutrophils is paralleled by their reduced capacity to bind the synthetic chemotactic peptide N-formylmethionylleucylphenylalanine (FMLP), as well as C5a. Furthermore, there is a reduction in the amount of glycoprotein 110, a neutrophil membrane matrix component and differentiation antigen which is associated with FMLP- and possibly also C5a-mediated chemotaxis. Reduction of C5a and of FMLP ligand binding, decreased expression of GP-110, and reduced neutrophil chemotaxis are consistent with a stem cell maturation error in LJP patients. This is further supported by studies demonstrating increased expression of CR2, the C3d/EBV receptor, on peripheral blood neutrophils of LJP patients. CR2 receptors are normally present on immature human neutrophils but are lost during the maturation process. These alterations in neutrophil surface components and their reduced chemotaxis may result from a genetically determined abnormality. Studies demonstrating the familial nature of both the neutrophil chemotactic disorder and the clinical entity represented by localized juvenile periodontitis point to a strong role for genetic determinants in the disease which affect neutrophil surface receptors.

Effects of experimental loss of teeth on the temporomandibular joint

A review is presented of the effects of loss of teeth, with impaired occlusal stabilization, on the temporomandibular joint in experimental animals. Loss of teeth, with subsequent abnormal loading of the temporomandibular joint, leads to histomorphological, pathological and pathophysiological changes in the articular cartilages, the articular disc, the synovium, and the bony articular components. The severity of the changes increases with increasing age, and an existing arthritis of the joint is aggravated by impaired occlusal stabilization. The experimentally induced changes resemble those in human subjects with extensive loss or extensive attrition of teeth.

Interleukin-2 production and bone-resorption activity in vitro by unstimulated lymphocytes extracted from chronically-inflamed human periodontal tissues

Lymphocytes isolated from chronically-inflamed tissues were assessed for their ability to produce lymphokines without further stimulation in vitro. Cells were extracted from tissue obtained from 42 patients undergoing periodontal surgery. Cultures were set up in triplicate and supernatants collected after 48 h were assayed for interleukin-2 (IL-2) or bone-resorptive activity. IL-2 was assayed in the cultured supernatants from 20 patients using a previously-standardized T-cell growth assay, with maximally-stimulated peripheral blood-lymphocytes as a positive control. Bone-resorptive activity (BRA) was assessed in culture supernatants from another 22 patients using an in-vitro mouse-calvaria culture-system in which calcium release was measured with a calcium analyser. IL-2 was detected in 12 out of the 20 unstimulated cultures; BRA was detected in 14 of the 22 unstimulated cultures. There appeared to be no relationship between IL-2 production and BRA and the severity of the disease as assessed by loss of attachment. Nevertheless, it seems that most of the cells extracted from chronically-inflamed tissue were producing lymphokines which may indicate stimulation in vivo prior to cell extraction.