Analysis of lymphocyte populations extracted from chronically inflamed human periodontal tissues. I. Identification

Diagnostic biomarkers for oral and periodontal diseases

This article provides an overview of periodontal disease diagnosis that uses clinical parameters and biomarkers of the disease process.This article discusses the use of biomarkers of disease that can be identified at the tissue, cellular, and molecular levels and that are measurable in oral fluids such as saliva and gingival crevicular fluid. Biomarkers identified from these biologic fluids include microbial, host response, and connective tissue-related molecules that can target specific pathways of local alveolar bone resorption. Future prospects for oral fluid-based diagnostics that use micro-array and microfluidic technologies are presented.

Actinobacillus actinomycetemcomitans-induced periodontal disease in mice: patterns of cytokine, chemokine, and chemokine receptor expression and leukocyte migration

Although the pathogenesis of periodontal disease (PD) is not well known, cytokines, chemotactic factors and inflammatory cells are certainly involved in the disease outcome. Here, we characterized the evolution of the PD induced by Actinobacillus actinomycetemcomitans in mice, showing that oral inoculation of these bacteria leads to the migration of leukocytes to periodontal tissues and marked alveolar bone resorption. We found the expression of pro-inflammatory and Th1-type cytokines including TNF-alpha, IFN-gamma and IL-12 in periodontal tissues after infection with A. actinomycetemcomitans, from the early stages after infection and throughout the course of the disease. Similar kinetics of expression were found for the chemokines CCL5, CCL4, CCL3 and CXCL10 and for the receptors CCR5 and CXCR3, all of them linked to the Th1-type pattern. The expression of the Th2-type mediators IL-10, CCL1 and their receptors CCR4 and CCR8 was detected only after 30 days of infection, determining a time-dependent mixed pattern of polarized immune response. The chemokine expression was correlated with the presence of polymorphonuclear leukocytes, macrophages, CD4 and CD8 lymphocytes, and B cells in the inflammatory infiltrate. Interestingly, during the predominance of the Th1-type response, a sharp increase in the number of inflammatory cells and intense bone loss was seen. By contrast, after the increased expression of Th2-type mediators, the number of inflammatory cells remained constant. Our data demonstrate that mice subjected to oral inoculation of A. actinomycetemcomitans represent a useful model for the study of PD. In addition, our results suggest that expression of cytokines and chemokines can drive the selective recruitment of leukocyte subsets to periodontal tissues, which could determine the stable or progressive nature of the lesion.

Generation of gingival T cell lines/clones specific with Porphyromonas gingivalis pulsed dendritic cells from periodontitis patients

OBJECTIVES AND BACKGROUND

It is well documented that in periodontitis lesions, most infiltrated gingival T cells are antigen-specific memory T cells. These cells play an important role as regulators and effector cells in the pathogenesis of periodontitis. In this study, we used dendritic cells (DCs) as antigen-presenting cells to generate human gingival T cell lines and clones specific for Porphyromonas gingivalis from periodontitis patients.

METHODS

Autologous DCs were derived from the patients' adherent monocytes using granulocyte-macrophage colony-stimulating factor and interleukin (IL)-4. Lymphocytes were isolated from gingival biopsies using collagenase enzyme digestion and the number was increased by subsequent culturing in IL-2-containing medium. T cells were then negatively sorted using flow cytometry, cocultured with P. gingivalis-pulsed DCs and subsequently expanded in the culture medium containing IL-2. T cells were kept viable and active by periodic exposure to antigen-pulsed DCs. The specificity of the T cell lines was tested against four plaque bacteria: P. gingivalis, Actinobacillus actinomycetemcomitans, Prevotella intermedia and Actinomyces viscosus. The established T cell lines were then cloned. Three P. gingivalis-specific T cell lines and 12 gingival T cell clones were generated. They all showed good specificity against P. gingivalis but not to other plaque bacteria.

RESULTS

All T cell clones were positive for CD4 and the majority of them produced interferon gamma, but a minimal or negligible amount of IL-5.

CONCLUSIONS

The data obtained clearly showed that monocyte-derived DCs could be used as powerful antigen-presenting cells to generate antigen-specific T cells from periodontitis tissues.

Upregulation of co-stimulatory molecule expression and dendritic cell marker (CD83) on B cells in periodontal disease

T cells and their cytokines are well known for their important role in the pathogenesis of periodontitis. To date, the role of antigen presenting cells (APCs), which are known to be critical in the regulation of T cell response, has been poorly investigated in periodontitis. In this study, we analyzed the expression of co-stimulatory molecules (CD80 and CD86) and CD83, which is a marker of mature dendritic cells, on gingival cells that were isolated from severe periodontitis tissues, with the use of flow cytometry. Significant upregulation of CD86 and CD83 expression was detected in periodontitis lesions, and most of this occurred on B cells. In vitro peripheral blood mononuclear cell cultures showed that stimulation with different periodontopathic bacteria, that included Porphyromonas gingivalis, Actinobacillus actinomycetemcomitans, Prevotella intermedia, and Actinomyces viscosus, upregulated both CD86 and CD83 expression on B cells. Therefore, the presence of plaque bacteria may be responsible for the enhanced expression seen in vivo on gingival B cells. APC function by bacterial-activated B cells was further investigated using allogeneic mixed leukocyte reactions. After 24 h culture with either A. actinomycetemcomitans or P. gingivalis, these activated B cells performed as potent APCs in mixed leukocyte reactions, and they stimulated T cells to produce high levels of gamma interferon and minimal interleukin-5. In conclusion, periodontopathic bacterial-induced B cell activation with upregulation of CD86 and CD83 may be associated with enhanced APC function. The results of this study suggest, therefore, that infiltrated gingival B cells have a possible role as APCs in the regulation and maintenance of local T cell response in periodontitis.

Immunohistological study of interferon-gamma- and interleukin-4-bearing cells in human periodontitis gingiva

The purpose was to investigate the balance between interferon (IFN)-gamma- and interleukin (IL)-4-bearing cells in various human inflamed gingiva by immunohistochemistry. Gingival tissues obtained from patients with gingivitis or periodontitis were divided into three groups based on the degree of histopathological inflammation, mild, moderate and severe. The tissues were also divided into four groups according to the clinical probing depth (PD). IFN-gamma- and IL-4-bearing cells in gingival tissues were stained immunohistologically and counted. The ratio of IL-4-bearing cells to IFN-gamma-bearing cells was calculated for each section. IFN-gamma-bearing cells were widespread in the connective tissue and their number increased significantly with the severity of inflammation and an increase of PD. IL-4-bearing cells were located beneath the pocket epithelium and their number showed no significant differences among the inflammation or PD groups. The ratios of IL-4-bearing cells to IFN-gamma-bearing cells in the severe inflammation or deep PD groups were significantly lower than those in the moderate inflammation or shallow PD groups. These results suggest that a low ratio of IL-4-bearing cells to IFN-gamma-bearing cells might be involved in the destruction of periodontal tissue.

CD29 expression on CD4+ gingival lymphocytes supports migration of activated memory T lymphocytes to diseased periodontal tissue

The cell surface phenotypes of CD+ cells extracted from inflammatory periodontal disease tissues were analyzed using two- and three-color immunofluorescence and flow cytometry. Cells extracted from both adult periodontal and localized juvenile periodontitis lesions showed a depressed CD4/CD8 ratio (1.0 +/- 0.1 adult periodontitis and 1.1 +/- 0.1 localized juvenile periodontitis) compared with cells recovered from normal/marginal gingivitis tissue (1.8 +/- 0.2) or with normal peripheral blood cells (2.1 +/- 0.1) or periodontal disease blood cells (2.1 +/- 0.1 and 1.7 +/- 0.1 for adult periodontitis and juvenile periodontitis, respectively). The monoclonal antibodies anti-2H4 and anti-4B4 were used to identify the CD45RA and CD29 antigens respectively on CD4+ T cells from the periodontal disease lesions. In peripheral blood. CD29+ cells accounted for 66-77% of the CD4+ population, and CD45RA+ cells accounted for 22-27% of the CD4+ subset. No differences in expression were found between peripheral blood lymphocytes from normal subjects and from periodontal disease patients. Two-color analyses of lymphocytes from periodontal diseased tissues showed that 87-89% of the CD4+ population were CD29+ and that 70-79% of the CD4+ cells were CD45RA+. Normal tissues contained significantly fewer CD4+CD29+ cells (56 +/- 4%) and CD4+CD45RA+ cells (40 +/- 4%) on average, and few, if any double-labelled cells could be accounted for. These data implied that a significant percentage of the CD4+ cells from the diseased tissues were both CD29+ and CD45RA+ and that these populations are found in quite different proportions in diseased periodontal tissue than in peripheral blood or nondiseased tissue. In further analyses using three-color cytometry the mean percentage of CD4+ CD29+ CD45RA+ lymphocytes extracted from periodontal disease lesions was 43 +/- 9% of the CD4+ population. These results suggest that CD4+ T lymphocytes in periodontal disease not only demonstrate varying levels of maturity but also that the accumulation of CD4+ T cells within the periodontal tissues may be a result of increased adhesion and transendothelial migration.

Cloning, characterization, and antigen specificity of T-lymphocyte subsets extracted from gingival tissue of chronic adult periodontitis patients

Chronic periodontitis is characterized by dense infiltrations of B and T lymphocytes within the gingival connective tissue. Distinct anaerobic gram-negative bacteria as well as autoimmunity to collagen have been reported to play a role in the etiology and the pathogenesis of this disease. Here we describe the cloning and characterization of CD4+ and CD8+ T lymphocytes isolated from inflamed gingival tissue obtained from four patients with chronic periodontitis. Clones were raised with phytohemagglutinin and interleukin-2 and tested for proliferation in response to whole-cell antigens of Porphyromonas gingivalis, Prevotella intermedia, Actinobacillus actinomycetemcomitans, human collagen type I, and two bacterial heat shock proteins. CD4+ T-cell clones reactive with collagen type I were obtained from all four patients. Eighty percent of these clones had phenotypes resembling the mouse type 2 T helper (Th) phenotype, i.e., they produced high levels of interleukin-4 and low levels of gamma interferon. No collagen-type-I-reactive CD8+ clones were obtained. Bacterial-antigen-reactive CD4+ and/or CD8+ T-cell clones were also obtained from each patient, and the majority of the clones showed a Th0-like cytokine pattern and produced equal amounts of interleukin-4 and gamma interferon. Although most clones were reactive with P. intermedia, it seems that the immune response is not strictly directed against this particular microorganism, as clones reactive with one of the other bacteria were also obtained from two patients. We propose that collagen-specific CD4+ Th2-like T cells contribute to the chronicity of periodontitis but that their modes of activation might be controlled by Th0-like T cells specific for periodontitis-associated bacteria.

Gingival cell IL-2 and IL-4 in early-onset periodontitis

The purpose of this study was to compare, using cell blot analysis, the association of gingival tissue mononuclear cells (GTMC) isolated from lesions displaying histories of early-onset periodontitis (EOP; typically B-lymphocyte dominated) and gingivitis (typically T-lymphocyte dominated) with the B-cell stimulating cytokine, interleukin (IL)-4, and the T-cell stimulating cytokine, IL-2. Eleven EOP patients and 11 age- and gender-similar gingivitis control (GC) subjects participated. Gingival tissue adjacent to the alveolar crest normally removed during surgery was digested in collagenase-containing media and GTMC were isolated by density gradient centrifugation. Cells were separated into four aliquots. One was left unstimulated; the remainder were stimulated for 2 hours with Porphyromonas gingivalis outer membrane protein, mitogen Concanavalin A, or common antigen tetanus toxoid. Cells then were centrifuged onto transfer membranes and incubated in RPMI 1640 media for 6 hours to allow absorption of secreted cytokine. Membranes were treated with monoclonal anti-IL-2 or anti-IL-4, followed by a biotin-conjugated second layer, streptavidin-alkaline phosphatase and nitro blue tetrazolium/5-bromo-4-chloro-indolyl-phosphate (NBT/BCIP) color development. A higher percentage of GTMC from EOP patients were IL-2+ when stimulated with P. gingivalis compared with GTMC from GC patients (20 +/- 2% vs. 12 +/- 2%, P < 0.003). A higher percentage of non-stimulated GTMC from EOP patients produced IL-4 than from GC (22 +/- 4% vs. 6 +/- 3%, P < 0.00007), as well as when stimulated with P. gingivalis (22 +/- 3% vs. 13 +/- 2%, P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Clonal expansion of lymphocytes from oral lichen planus lesions

Lymphocytes were extracted from 11 biopsy specimens of oral lichen planus (OLP) by collagenase digestion, and cell lines were expanded with repetitive cycles of stimulation (with phytohaemagglutinin) and rest in media supplemented with interleukin 2. Four OLP lines contained a majority of CD3+CD4-CD8+ cells, in six lines the CD4:CD8 ratio was between 1 and 2, and in one line the CD4:CD8 ratio was 5:1. Limiting dilution of nine lines at 0.3 and 1.0 cells/well resulted in viable wells (putative clones) with plating efficiencies ranging from 0.0 to 18.1 percent and 0.0 to 22.2 percent respectively. The majority of clones were CD3+CD4-CD8+alpha beta+gamma delta-, although three clones were CD3+CD4+CD8-alpha beta+gamma delta- and one clone was CD3+CD4-CD8- and expressed the gamma delta T cell receptor. T cell clones derived from lymphocytes extracted from OLP lesions may be generated and maintained in culture providing opportunity for their further phenotypic and functional characterisation. This strategy may facilitate the identification of a putative oral lichen planus-specific antigen and indicate the frequency of lichen planus-specific T cells within lesions of OLP.

Immunosuppressive effect induced by Actinobacillus actinomycetemcomitans: effect on immunoglobulin production and lymphokine synthesis

The soluble sonicated extract (SE) from Actinobacillus actinomycetemcomitans inhibited primary T cell-dependent antibody responses in vivo. The production of IgG and IgM to sheep red blood cells (SRBC) was depressed when mice were treated with high concentrations of SE plus SRBC. Preinjection of SE 3 days prior to SRBC completely inhibited IgG production. SE plus SRBC-primed mice showed markedly depressed CD4/CD8 ratios relative to phosphate-buffered saline plus SRBC- or SRBC-immunized mice. SE-sensitized mice showed low blastogenic activity to concanavalin A (Con A) depending on sensitized periods induced by SE. This inhibitory mechanism was, in part, clarified by a suppression of IL-2 synthesis, IL-2 receptor expression and IL-6 secretion by the splenic T cells stimulated with Con A. These results support the hypothesis that the severe infection of A. actinomycetemcomitans suppresses the immune response by affecting CD4/CD8 ratios, followed by lymphokine production and finally antibody responses.

A Comparison of T4:T8 Lymphocyte Ratio in the Periodontal Lesion of Healthy and HIV-Positive Patients

Previous reports describe a characteristic, rapidly progressive, periodontitis that is unique to patients who are seropositive for HIV antibody (Western blot +). The purpose of this study was to compare the T4 and T8 lymphocyte subpopulations in the peripheral blood and periodontal lesions of these HIV patients with those of healthy controls. T-cell subsets in peripheral blood were quantified by flow cytometry. The values from this analysis were used to calculate the peripheral T4:T8 lymphocyte ratio for each patient. Gingival tissue (papilla) was obtained from 8 HIV+ patients and from 6 healthy HIV- control patients during routine gingival surgery. The T-cell subpopulations in the gingival tissue were determined using serial cryostat sections that were labeled with monoclonal antibodies for T4 and T8 cells and developed using an avidin-biotin-peroxidase system. Six sections were taken from each of the 14 tissue specimens (one per patient). The sections were examined at 450 x and the mean number of T4 and T8 cells calculated for each section. These mean values were then used to determine the T4:T8 lymphocyte ratio for each tissue specimen. The peripheral blood analysis revealed a mean serum T4:T8 ratio of (2.07 +/- 0.455) for the controls and (0.58 +/- 0.26) for the HIV patients. The significantly lower T4:T8 ratio in HIV patients is consistent with their diagnosis. Although the results indicated that the mean T4:T8 lymphocyte ratio in the gingiva of controls was highly variable (2.70 +/- 1.344), the gingiva of HIV patients consistently exhibited a complete absence of T-cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Determination of lymphocyte populations and subpopulations extracted from chronically inflamed human periodontal tissues

The lymphocyte populations and subpopulations extracted from inflamed periodontal tissues of patients with adult periodontitis were determined. 34 patients were grouped according to the gingival index score (GI) of 1, 2 and 3. Gingival tissue from 2 involved teeth was excised, treated with collagenase, and infiltrating cells were isolated and identified using monoclonal antibodies for lymphocyte sets and subsets. The % of CD3+ cells was about 54.5% in all 3 patient groups, but the percentage of CD22+ cells increased from 28.9 +/- 3.3% in the group with GI = 1 to 33 +/- 1.2% in the group with GI = 3. %s of CD4+ cells and activated CD4+ cells increased from 30.2 +/- 2.1% and 4.7 +/- 1.7% in the group with GI = 1 to 38.4 +/- 1.2% and 16.0 +/- 3.4% in the group with GI = 3, respectively, while in the same groups, the % of CD8+ cells decreased from 24.9 +/- 2.0% to 17.7 +/- 1.6%. These data indicate a possible importance of activated CD4+ cells in pathogenetic mechanisms of periodontitis.

Phenotypic analysis of B-cells extracted from human periodontal disease tissue

B-cells extracted from periodontal disease tissue were analyzed for the presence of activation markers using a range of monoclonal antibodies. In adult periodontitis (AP), 6% of B-cells expressed the IL-2 receptor (CD25) compared with 1-2% in peripheral blood and healthy or marginal gingivitis (H/MG) gingival B-cells. There was also an increase in the mean percentage of IgD-positive B-cells and a decrease in CD21 and CD22 expression. In both AP and H/MG lesions, 20-22% of the B-cells expressed CD23 compared with less than 5% in peripheral blood. As B-cells are activated by day 3 in culture and start differentiating into immunoglobulin-secreting cells by day 6, B-cell phenotypes were assayed at these times in this study. Following stimulation with the periodontopathic bacterium Porphyromonas gingivalis, the expression of CD23, CD21 and CD22 on B-cells extracted from AP lesions remained relatively constant over the 6-d culture period. However, with Fusobacterium nucleatum stimulation, there was a significant decrease in CD23, CD21 and CD22 expression after 3 d in culture, which corresponds to the activation time for B-cells. These results show that B-cells extracted from periodontal disease tissue display a range of activation markers and on stimulation, demonstrate differing responses to individual periodontopathic bacteria.

Importance of the host response in the periodontium

Immunological mechanisms have been implicated in the pathogenesis of periodontal disease for over 25 years. Studies throughout the 1970s established that advanced forms of the disease were dominated by B-cells/plasma cells while early and putative stable forms of the disease were dominated by T-cells/lymphocytes. Based on these observations, a model of disease was put forward which highlighted a possible T-cell/macrophage immunoregulatory imbalance being involved in disease pathogenesis. Studies throughout the 1980s have supported such a concept although the precise nature of this imbalance remains elusive. At the same time, clinical studies have established that patient susceptibility may be of overriding importance in determining disease outcome. In this context therefore, factors which influence this susceptibility should be fundamental in determining periodontal disease activity. These factors may include genetic variation between individuals in the way in which they respond to periodontopathic bacteria upon which environmental factors would be superimposed. These environmental factors would include anything that altered the balance between the host and the parasite and may be as diverse as recent viral infections resulting in T-cell anergy or physical and mental stress. Recent studies have shown that in elite atheletes, physical stress during training and competition leads to a suppression of mucosal immunity as evidenced by a reduction in salivary IgA. The subsequent effect of these environmental factors at the level of the periodontium, however, remains to be determined.

In situ lymphocyte subpopulations from active versus stable periodontal sites

The purpose of this study was to evaluate lymphocyte subset densities and distributions within gingival biopsies from active sites (greater than or equal to 2 mm clinical attachment loss within three months of biopsy) versus clinically similar but stable or healthy sites. Small interproximal gingival biopsies representing at least one of each of the above categories were obtained from each of 20 periodontal maintenance patients. Serial cryostat sections displaying a cross section of the gingiva were labeled with monoclonal antibodies for (1) pan T cells, (2) T cytotoxic/suppressor cells, (3) T helper/inducer cells and (4) pan B cells and were developed using an avidin-biotin-peroxidase system. Lymphocyte populations were enumerated in repeatable fields from the sulcular, middle and oral one-third of each section. Relative proportions of the same lymphocyte subsets were analyzed in peripheral blood samples from the same patients using direct immunofluorescence. Pan B cells were significantly more prevalent in infiltrates from active sites than in stable (P less than 0.05) or healthy (P less than 0.01) sites. The T/B cell ratio was also significantly lower in active than stable biopsies (P less than 0.05), and in active biopsies versus blood (P less than 0.05). The T helper/T suppressor cell ratio did not vary significantly between blood and any gingival tissue disease group or location, but a trend toward lower relative numbers of T helper cells in the sulcular infiltrates of active sites was noted. These results support the premise that active periodontal sites display elevated B cell populations and abnormal immune regulation possibly involving the T helper cell subset.

Human T-lymphocyte subpopulations in periapical lesions

Both B-lymphocyte-and T-lymphocyte-mediated immunologic reactions have been implicated in the pathogenesis of human periapical lesions. The purpose of this study was to identify various subpopulations of T-lymphocytes in these lesions. Fifteen periapical lesions were obtained during periapical surgery. Each specimen was quick-frozen and stored in liquid nitrogen. Immunoperoxidase staining for the presence of T-lymphocyte subpopulation, was done with the use of the monoclonal antibody and Vecta-stain ABC/peroxidase kit. Cryostat tissue sections were incubated with 3% normal horse serum. Specific monoclonal antibody (Coulter T4, T8, T11) was placed on the section, washed, and then covered with biotinylated antibody to mouse IgG. After TRIS HC1 washing, the ABC/peroxidase solution was placed on the section and 3,3-diaminobenzidine was applied; the section was washed and then counterstained with 2% methyl green. After dehydration, sections were mounted and examined under the light microscope. The presence of lymphocytes was confirmed by the appearance of brown rings around cells with lymphocyte morphology. Fourteen lesions were diagnosed as granuloma and stained positively for pan T-lymphocytes (T11), T helper cells (T4), and T cytotoxic cells (T8). The remaining specimen, diagnosed as an apical scar, contained no T-lymphocytes. The presence of T-cells in periapical lesions indicates that cell-mediated reactions participate in the pathogenesis of these lesions.

Phenotypic and functional analysis of T cells extracted from chronically inflamed human periodontal tissues

T-cell subsets extracted from chronically inflamed periodontal tissues were identified using monoclonal antibodies, and their functional activity was analysed using the autologous mixed lymphocyte reaction (AMLR). Tissue was obtained from a total of 33 adult periodontitis (AP) patients and 6 normal/marginal gingivitis (N/MG) patients. All AP patients had received repeated oral hygiene instruction and root planing prior to the surgery, and the majority (30 out of 33) had at least one site with greater than 6 mm loss of attachment from the cementoenamel junction within the surgical field. The N/MG patients had no loss of attachment, and probing depths were less than 3 mm. Single cell suspensions were obtained following collagenase digestion (90 minutes at 37 degrees C) and mechanical disruption of the tissue. T-cell subsets were identified using an indirect immunofluorescence assay on cells obtained from 19 AP patients and the 6 N/MG patients. The mean (+/- standard error) helper:suppressor (T4:T8) ratio for the AP patients was found to be 0.94 +/- 0.48 compared with 1.65 +/- 0.16 for the N/MG group and 1.51 +/- 0.12 for peripheral blood controls. HLA-DR positive macrophages were identified and were found to include both acid phosphatase (AcP) positive and adenosine triphosphatase (ATPase) positive populations. Functional analysis was carried out using cells extracted from the remaining 14 AP patients. Cells from six of these 14 patients were found to be capable of spontaneous proliferation. Co-culture experiments using autologous T and non-T populations revealed that cells from only four patients were able to respond in an AMLR while those from only one of the 14 patients were able to stimulate the AMLR.(ABSTRACT TRUNCATED AT 250 WORDS)

Phenotypic analyses of mononuclear cells recovered from healthy and diseased human periodontal tissues

Mononuclear cells were recovered from the gingival tissues of normal individuals and from patients with periodontal disease. Lymphocyte phenotypic markers were identified by immunofluorescence after reaction with monoclonal antibodies to T-cell subset markers. The normal tissues exhibited T4/T8 ratios almost identical to those in the peripheral blood. The diseased tissue cell ratios were significantly reduced, in both the adult periodontitis and the juvenile periodontitis groups (P less than 0.01 and P less than 0.02, respectively), indicating alterations in the T-cell subset distribution in these tissues. Each diseased patient showed a much decreased T4/T8 ratio in the gingival lymphocytes when these were compared with the peripheral blood ratio from the same patient. The T4/T8 ratios of the more severe sites were significantly lower than those of the less severe sites in the same disease category. The decreases in subset ratios could be attributed to statistically significant reductions in T4+-lymphocyte recoveries relative to peripheral blood and also to slight relative increases in T8+ lymphocytes. A highly significant (P less than 0.001) correlation between the average probeable periodontal pocket depth and the T4/T8 ratio of each disease category was demonstrated. The relative recoveries of B cells from the various tissues did not differ between diseased and normal tissues. It is suggested that T-cell regulatory expression in gingival tissues is distinct from peripheral blood regulatory expression and that there is a local immunoregulatory imbalance in periodontal disease.

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.

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.