Host tissue response in chronic periodontal disease. VI. The role of cell-mediated hypersensitivity

Immunologic mechanisms of pathogenesis in periodontal diseases: an assessment

Principal lines of evidence that immune reactions are central to the pathogenesis of periodontitis are reviewed. Necessary components of immunologic reactions are present in gingiva in the periodontal diseases. Differences between healthy and periodontitis patients with respect to some measures of immune function further indicate that immune reactions do occur in the gingiva during periodontitis. They are probably responsible for at least some of the destruction of connective tissue and bone that occurs. Classical antibody-mediated hypersensitivity reactions probably do not provide the reasons. Mechanisms are more likely to be found in the pro-inflammatory and tissue-degrading effects of cytokines released in host-protective, antigen-specific and polyclonal responses to oral bacterial constituents or products. Some evidence suggests that limitation of clinical destruction in localized early onset periodontitis (JP) may in part be a function of a protective antibody response which develops after an initial rapidly progressive infection. A relatively deficient immune responsiveness may allow progression to more severe and generalized disease (RPP). Suggestions are made for studies needed to confirm suspected pathogenetic mechanisms, approach resultant targeted therapies, and test hypotheses for contrasting roles of immune reactions in different clinical expressions of periodontitis.

Microbiological and immunological aspects of experimental periodontal disease in rats: a review article

Animal models in which microbiological and immunological aspects of periodontal disease can be studied prospectively seem well warranted. The rat bears much resemblance to man with respect to periodontal anatomy, development and composition of dental plaque, histopathology of periodontal lesions, and basic immunobiology. Furthermore, reproducible methods are available for assessment of periodontal disease in rats, and detectable periodontal destruction can be induced in a few weeks in these animals without traumatizing periodontal tissues with ligatures. Experimental periodontitis studies in germ-free rats have confirmed the pathogenicity of several suspected periodontal pathogens (Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Capnocytophaga sputigena, Eikenella corrodens, and Fusobacterium nucleatum). The studies also suggest that the number of periodontal pathogens may be higher than generally believed, since species like Streptococcus sobrinus and Actinomyces viscosus are associated with periodontal bone loss in rats. Studies in rats with congenital or induced immune defects indicate that generalized or selective immunosuppression at the time of infection with periodontal pathogens may aggravate periodontal disease. Studies in immunized rats indicate that periodontal disease can be prevented by immunization against periodontal pathogens. However, it is also possible by immunization to induce periodontal destruction; i.e., the immune system has a destructive potential which should not be overlooked. In the future, the rat model may prove valuable for initial screening of antigen preparations and immunization regimens in the search for a periodontitis vaccine.

The role of histopathology in the diagnosis and prognosis of periodontal diseases

The histological evaluation of surgical biopsies from affected tissues is a standard way of assessing pathological change and determining treatment in many diseases. In most forms of periodontal disease, however, this approach finds limited application. Here, we review what uses the histopathological approach has in the study and evaluation of the periodontal diseases. Current understanding of the changes in epithelial anatomy during pocket formation, the cellular composition and dynamics of the inflammatory infiltrate and the mechanisms of bone resorption and repair are reviewed from the perspective of the information available from microscopical investigation, including the uses and potential application of modern immunocytochemical methods to these questions. The usefulness of histological study of biopsy material is reassessed in the light of advances made in immunohistochemical techniques and their application to gingival inflammatory infiltrates and epithelia. Such techniques offer immediately valuable research opportunities with potential for diagnostic applications, noteably the recognition of phases of destructive activity and their differentiation from periods of effective host defence.

Periodontal alterations in patients with pemphigus vulgaris taking steroids. A biannual assessment

Periodontal health parameters and salivary cortisol were studied in 19 adult pemphigus vulgaris patients on chronic steroid therapy. The patient population was divided into non-medicated and medicated subjects at intake into the study. A significant difference between the 2 examinations, performed at an interval of 8.73 months +/- 4.35, was found in bleeding index (p less than 0.000 and p less than 0.04, respectively) and gingival recession (p less than 0.000 and p less than 0.009) in both groups. No changes occurred in alveolar bone height. Steroid therapy altered the bleeding index (R = 0.60 and R = 0.80) and gingival recession (R = 0.87 and 0.91) in a dose-related manner, and induced low salivary cortisol. The findings of this study would suggest suppression of the host inflammatory reaction, resulting in an alleged healthy clinical appearance of the periodontium.

Gingivitis

Gingivitis is caused by substances derived from microbial plaque accumulating at or near the gingival sulcus; all other suspected local and systemic etiologic factors either enhance plaque accumulation or retention, or enhance the susceptibility of the gingival tissue to microbial attack. Microbial species specifically associated with gingival health include Streptococcus sanguis 1, S. D-7, and Fusobacterium naviforme. Bacteria involved in the etiology of gingivitis include specific species of Streptococcus, Fusobacterium, Actinomyces, Veillonella, and Treponema and possibly Bacteroides, Capnocytophaga, and Eikenella. Microbial colonization and participation is sequential, with the complexity of the associated flora increasing with time. The pathogenesis has been separated into the initial, early, and established stages, each with characteristic features. The initial lesion is an acute inflammation which can be induced experimentally by application of extracts of plaque bacteria to normal gingiva. The early lesion is characterized by a lymphoid cell infiltrate predominated by T lymphocytes, characteristic of lesions seen at sites of cell-mediated hypersensitivity reactions. The early lesion can be induced by application of purified contact antigens to the gingival tissues of previously sensitized animals. As the clinical condition worsens, the established lesion appears, predominated by B lymphocytes and plasma cells. Established lesions may remain stable for indefinite periods of time, they may revert, or they may progress. Periodontal destruction does not result from the conversion of a predominantly T cell to a predominantly B cell lesion as has been suggested, but rather from episodes of acute inflammation. Clinical manifestations of gingivitis are episodic phenomena characterized by discontinuous bursts of acute inflammation. Most lesions are transient or persistent but not progressive. Attachment loss may precede alveolar bone loss and may occur without the manifestations of a concurrent or a precursor gingivitis. On the other hand, the evidence indicates that a portion of gingivitis lesions can and does progress to periodontitis. Gingivitis and the periodontal microflora differ in children and adults. Clinical signs of gingivitis either do not appear as plaque accumulates, or they are greatly delayed in children, and the inflammatory infiltrate consists mostly of T lymphocytes. The conversion to a B cell lesion does not appear to occur. The evidence supports the conclusion that gingivitis is a disease, and that control and prevention is a worthwhile goal and a health benefit.(ABSTRACT TRUNCATED AT 400 WORDS)

Cell populations associated with gingival bleeding

The presence of crevicular bleeding after probing is an objective clinical sign of gingival inflammation. It has been associated with a plasma cell-dominated inflammatory infiltrate in deep pockets and has been suggested as an indication of active periodontitis. The purpose of this study was to characterize the cellular composition of gingival connective tissue associated with shallow pockets which bled after probing. Prior to biopsy, the mid-facial gingiva associated with 30 teeth from 26 patients was assessed for the presence or absence of visual inflammation, pocket depth and bleeding after probing with a standardized force of 25 g. A horizontal reference incision was made on the facial aspect of the gingiva to demarcate for histologic analysis the specific gingival area probed and evaluated for inflammation. Cell populations were determined from histological sections using morphometric point counting techniques in six standard fields at and coronal to the level of the reference incision. The percentage of cell types and the per cent volume densities of all tissue components were compared between clinically normal and inflamed gingiva. In clinically inflamed gingiva there was a significantly greater percentage of lymphocyte/macrophage/monocyte cells and a smaller percentage of fibroblast/endothelial cells. The percentage of plasma cells was only a fraction of that found for other inflammatory cells. The results of this study indicated that a lesion in the gingiva associated with bleeding after probing can consist of an inflammatory infiltrate which is not dominated by plasma cells.

Cross-sectional study of the effects of immunosuppressive drugs on chronic periodontal disease in man

Oral examinations were performed on 102 patients receiving immunosuppressive drug therapy following renal transplantation. A further 111 control patients matched for age and sex, were also examined. The severity of dental caries of the 2 groups was compared by considering their decayed, missing and filled teeth (DMF-T), and the severity of periodontal disease was compared in terms of pocket depths, Plaque, Calculus and Sulcular Bleeding Indices, and Russell's Periodontal Index. When comparing the 2 groups, note was made of restorations involving the gingival margins, the presence of partial dentures and recent and current antibiotic therapy. No significant differences were found between the groups with regard to age, sex distribution, plaque levels, DMF and Russell's Periodontal Index. The immunosuppressed group had significantly less calculus, fewer restorations involving the gingival margins and significantly lower mean pocket depth. However, they did have more gingival recession than the controls and also a higher Sulcus Bleeding Index. All differences seen were maintained even when patients from both groups on antibiotics were eliminated from the analysis. Within the immunosuppressed group no relationship was found between the length of time the drugs were taken and the periodontal variables. The study indicates that patients on immunosuppressive therapy show no change in susceptibility to destructive periodontal disease.

Cell-mediated cytotoxicity against rat fibroblasts induced by Actinomyces viscosus

Cell-mediated cytotoxicity against syngeneic fetal rat fibroblasts that require in vitro exposure of effector cells to Actinomyces viscosus Ny1 fractions was investigated by measuring the uptake of radioactivity by fibroblasts during a 2-h pulse with [14C]aminoisobutyric acid after 1 to 3 days of coculture with splenic effector cells. By using splenocytes from inbred RIC-Sprague-Dawley rats as effector cells and syngeneic embryonic rat fibroblasts as target cells, strong cell-mediated cytotoxicity dependent on the in vitro exposure to an A. viscosus Ny1 fraction was observed, but only within a small range of effector-to-target cell ratios (3:1 to 10:1). Concanavalin A and lipopolysaccharide from Escherichia coli induced a comparable cytotoxicity, indicating that the effect might be connected with the mitogenic activity of the A. viscosus NY1 fraction. Splenocytes from rats immunized with A. viscosus Ny1 and from control rats induced similar levels of cytotoxicity in 72-h cytotoxicity assays. In shorter assays (24 h), however, splenocytes from immune animals induced low cytotoxicity, which was, however, significantly higher than that induced by splenocytes from control animals. We conclude that both antigen- and mitogen-dependent cell mediated effector mechanisms are operative in this system and that the two normally overlapping effects can be experimentally separated. This new system describes a fibroblast impairment in the presence of splenocytes and bacterial components and may provide a useful model for studying pathogenic mechanisms operative in periodontal disease.

Lymphocyte transformation responses in gingivitis and periodontitis. A review

Recent research in oral immunology has implied that cell-mediated immune reactions are a possible pathogenic mechanism in gingivitis and periodontitis. The basis for the most commonly used in vitro test, lymphocyte transformation, and the possible interpretation are explained. The application of this test to a study of medically healthy subjects with varying degrees of periodontal disease yielded conflicting results. Previous reports in the literature have not established a relationship between blastogenic responses of peripheral blood lymphocytes in periodontally diseased patients, and their disease status. The possibility of subclinical sensitization is discussed, although a cause-and-effect relationship has not been proven.

Conversion of a stable T-cell lesion to a progressive B-cell lesion in the pathogenesis of chronic inflammatory periodontal disease: an hypothesis

Changes in the host's immunological response or, alternatively, changes in the oral microflora have been implicated as possible mechanisms by which a stable lesion of chronic inflammatory periodontal disease may become a progressive lesion leading to tissue destruction and tooth loss. It has recently been established that the progressive lesion in humans can be unequivocally considered as a B-cell response. Circumstantial evidence exists which suggests that the stable lesion is in fact a T-cell-mediated mechanism. An hypothesis is presented to explain the change from a stable to a progressive state in terms of a shift from a predominantly T-cell lesion to one involving large numbers of B-cells. Mechanisms of this shift in cell populations are considered together with a discussion of possible means of preventing such a shift.

The immunopathogenesis of progressive chronic inflammatory periodontal disease

Natural, humoral and cellular immune mechanisms have all been implicated in the pathogenesis of chronic inflammatory periodontal disease. However, confusion still exists as to the role played by each of these immunological mechanisms. Recently, characterization of the cell types within the progressive lesion has been established, in which four recognizable zones were described. Immediately subjacent to the epithelium lining the periodontal pocket both polymorphonuclear leukocytes (PMN's) and macrophages were seen, while cells deeper in the tissues had the morphological appearance of lymphocytes. The majority of these lymphocytes had a B-cell phenotype although a few T-cells and macrophages were found. On the advancing front of the lesion the cells had the morphological appearance of plasma cells, the majority of which contained IgG. Other cells found in this region had the morphology of plasma cells yet contained no cytoplasmic immunoglobulin, but they did contain substantial amounts of lysosomal enzymes. Similar cells have previously been described in periodontal disease; their frequent association with fibroblasts may suggest that they are important in the pathogenesis. Deposits of IgG and fibrin were found in the fibrous tissue band surrounding the lesion. These results are reviewed and, although the zones described were not anatomically distinct, by describing the lesion in this way it was possible to establish a convenient model to explain the immunopathogenesis of progressive chronic inflammatory periodontal disease. In this respect, progressive chronic inflammatory periodontal disease in man should be considered as a B-cell lesion.