Polyclonal B-cell activation induced by extracts of Gram-negative bacteria isolated from periodontally diseased sites

Immunomodulation—What to Modulate and Why? Potential Immune Targets

Despite over 50 years of research into the immunology of periodontal disease, the precise mechanisms and the role of many cell types remains an enigma. Progress has been limited by the inability to determine disease activity clinically. Understanding the immunopathogenesis of periodontal disease however is fundamental if immunomodulation is to be used as a therapeutic strategy. It is important for the clinician to understand what could be modulated and why. In this context, potential targets include different immune cell populations and their subsets, as well as various cytokines. The aim of this review is to examine the role of the principal immune cell populations and their cytokines in the pathogenesis of periodontal disease and their potential as possible therapeutic targets.

Chemokines in Oral Inflammatory Diseases: Apical Periodontitis and Periodontal Disease

The inflammatory oral diseases are characterized by the persistent migration of polymorphonuclear leukocytes, monocytes, lymphocytes, plasma and mast cells, and osteoblasts and osteoclasts. In the last decade, there has been a great interest in the mediators responsible for the selective recruitment and activation of these cell types at inflammatory sites. Of these mediators, the chemokines have received particular attention in recent years. Chemokine messages are decoded by specific receptors that initiate signal transduction events, leading to a multitude of cellular responses, including chemotaxis and activation of inflammatory and bone cells. However, little is known about their role in the pathogenesis of inflammatory oral diseases. The purpose of this review is to summarize the findings regarding the role of chemokines in periapical and periodontal tissue inflammation, and the integration, into experimental models, of the information about the role of chemokines in human diseases.

Lymphocyte subpopulation in healthy and diseased gingival tissue

In this study, infiltrating lymphocytes subpopulation in gingival sections of healthy, inflamed, and periodontitis lesions was investigated. A set of cluster of differentiation (CD) antigen specific monoclonal/polyclonal antibodies to detect different cell types within the tissues was used. These included anti-CD3 (pan T-cell), anti-CD45RO (memory T-cell), anti-CD20 (B-cell), and kappa light chain (plasma cells). Biopsies of gingival tissue were obtained from 17 patients who had clinically healthy gingiva, from 18 patients with gingivitis, and 17 patients with periodontitis.

A significantly greater proportion of T-cells (P < 0.00) was observed in healthy gingival and gingivitis tissue samples compared to periodontitis tissue samples. In addition, a greater proportion of B-cells was observed in periodontitis lesions than in the gingival lesions (P < 0.00). The memory T-cells and the kappa light-chain plasma cells were present in both healthy and diseased tissues, suggestive of previous activation by periodontal pathogenic microorganisms.

In conclusion, these differences in the relative proportions of B- and T-cells may reflect a difference in the immunopathology of periodontitis and gingivitis lesions.

Destructive periodontitis lesions are determined by the nature of the lymphocytic response

It is now 35 years since Brandtzaeg and Kraus (1965) published their seminal work entitled "Autoimmunity and periodontal disease". Initially, this work led to the concept that destructive periodontitis was a localized hypersensitivity reaction involving immune complex formation within the tissues. In 1970, Ivanyi and Lehner highlighted a possible role for cell-mediated immunity, which stimulated a flurry of activity centered on the role of lymphokines such as osteoclast-activating factor (OAF), macrophage-activating factor (MAF), macrophage migration inhibition factor (MIF), and myriad others. In the late 1970s and early 1980s, attention focused on the role of polymorphonuclear neutrophils, and it was thought that periodontal destruction occurred as a series of acute exacerbations. As well, at this stage doubt was being cast on the concept that there was a neutrophil chemotactic defect in periodontitis patients. Once it was realized that neutrophils were primarily protective and that severe periodontal destruction occurred in the absence of these cells, attention swung back to the role of lymphocytes and in particular the regulatory role of T-cells. By this time in the early 1990s, while the roles of interleukin (IL)-1, prostaglandin (PG) E(2), and metalloproteinases as the destructive mediators in periodontal disease were largely understood, the control and regulation of these cytokines remained controversial. With the widespread acceptance of the Th1/Th2 paradigm, the regulatory role of T-cells became the main focus of attention. Two apparently conflicting theories have emerged. One is based on direct observations of human lesions, while the other is based on animal model experiments and the inability to demonstrate IL-4 mRNA in gingival extracts. As part of the "Controversy" series, this review is intended to stimulate debate and hence may appear in some places provocative. In this context, this review will present the case that destructive periodontitis is due to the nature of the lymphocytic infiltrate and is not due to periodic acute exacerbations, nor is it due to the so-called virulence factors of putative periodontal pathogens.

Antiproliferative activity of Actinobacillus (Haemophilus) actinomycetemcomitans and Fusobacterium nucleatum in peripheral blood mononuclear cells

Several studies indicate Actinobacillus (Haemophilus) actinomycetemcomitans and Fusobacterium nucleatum as etiologic agents of periodontal disease. Immunosuppressive factors produced by microorganisms probably contribute to the initiation and evolution of this disease. This study evaluated the antiproliferative activity of ammonium precipitate fractions of A. (H.) actinomycetemcomitans and F. nucleatum isolates from humans and marmosets both with and without periodontal disease. All A. (H.) actinomycetemcomitans and most F. nucleatum strains inhibited PBMC proliferation in a dose-dependent manner. The degree of cell proliferative inhibition of each bacterial species differed among the strains and was independent of host clinical status. The in vitro inhibition of stimulated lymphocyte proliferation induced by different A. (H.) actinomycetemcomitans and F. nucleatum isolates demonstrated the importance of this phenomenon in bacterial virulence, playing a possible suppressor role in host defense mechanisms in vivo. Moreover, our findings pointed out a marked difference between A. (H.) actinomycetemcomitans and F. nucleatum cytoplasmic extracts in their antiproliferative activity, regarding the antigen concentration required for maximum inhibition and their vulnerability to heating and proteolytic treatment.

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.

Effect of Fusobacterium nucleatum on the T and B cell responses to Porphyromonas gingivalis in a mouse model

T cell cytokine profiles and specific serum antibody levels in five groups of BALB/c mice immunized with saline alone, viable Fusobacterium nucleatum ATCC 25586, viable Porphyromonas gingivalis ATCC 33277, F. nucleatum followed by P. gingivalis and P. gingivalis followed by F. nucleatum were determined. Splenic CD4 and CD8 cells were examined for intracytoplasmic interleukin (IL)-4, interferon (IFN)-gamma and IL-10 by dual colour flow cytometry and the levels of serum anti-F. nucleatum and anti-P. gingivalis antibodies determined by an ELISA. Both Th1 and Th2 responses were demonstrated by all groups, and while there were slightly lower percentages of cytokine positive T cells in mice injected with F. nucleatum alone compared with the other groups immunized with bacteria, F. nucleatum had no effect on the T cell production of cytokines induced by P. gingivalis in the two groups immunized with both organisms. However, the percentages of cytokine positive CD8 cells were generally significantly higher than those of the CD4 cells. Mice immunized with F. nucleatum alone had high levels of serum anti-F. nucleatum antibodies with very low levels of P. gingivalis antibodies, whereas mice injected with P. gingivalis alone produced anti-P. gingivalis antibodies predominantly. Although the levels of anti-F. nucleatum antibodies in mice injected with F. nucleatum followed by P. gingivalis were the same as in mice immunized with F. nucleatum alone, antibody levels to P. gingivalis were very low. In contrast, mice injected with P. gingivalis followed by F. nucleatum produced equal levels of both anti-P. gingivalis and anti-F. nucleatum antibodies, although at lower levels than the other three groups immunized with bacteria, respectively. Anti-Actinobacillus actinomycetemcomitans, Bacteroides forsythus and Prevotella intermedia serum antibody levels were also determined and found to be negligible. In conclusion, F. nucleatum immunization does not affect the splenic T cell cytokine response to P. gingivalis. However, F. nucleatum immunization prior to that of P. gingivalis almost completely inhibited the production of anti-P. gingivalis antibodies while P. gingivalis injection before F. nucleatum demonstrated a partial inhibitory effect by P. gingivalis on antibody production to F. nucleatum. The significance of these results with respect to human periodontal disease is difficult to determine. However, they may explain in part differing responses to P. gingivalis in different individuals who may or may not have had prior exposure to F. nucleatum. Finally, the results suggested that P. gingivalis and F. nucleatum do not induce the production of cross-reactive antibodies to other oral microorganisms.

Large-scale early in vitro response to actinobacillus actinomycetemcomitans suggests superantigenic activation of T-cells

The mode of T-cell response to Actinobacillus actinomycetemcomitans is largely unknown. The present study sought to investigate the hypothesis that A. actinomycetemcomitans expresses superantigens, capable of antigen-non-specific T-cell activation. To that end, peripheral blood mononuclear cells were stimulated with A. actinomycetemcomitans, and T-cell expression of the early activation marker, CD69, was determined by flow cytometry. Results showed that A. actinomycetemcomitans activated a large number of T-cells with magnitude similar to that of staphylococcal enterotoxin superantigens. A. actinomycetemcomitans sonicate preferentially activated T-cells expressing Vbeta5.1 and Vbeta8, while the extracellular preparation activated Vbeta5.1+, Vbeta8+, and Vbeta12+ T-cells. T-cell response to A. actinomycetemcomitans was observed in the presence of autologous, as well as heterologous, antigen-presenting cells, suggesting a MHC-non-restricted response. Thus, the in vitro response to A. actinomycetemcomitans is characterized by large-scale T-cell activation in a Vbeta-specific and MHC-non-restricted manner, consistent with the involvement of superantigens.

The immune modulation of B-cell responses by Porphyromonas ginginvalis and interleukin-10

BACKGROUND

Polyclonal B-cell activation induced by periodontopathic bacteria has been cited as being important for elevated numbers of B cells, but the role of bacteria in the pathogenesis of periodontal disease remains unknown. In this study, we used an in vitro model to investigate the activation of immune cells by the periodontopathic bacterium Porphyromonas gingivalis in healthy subjects.

METHODS

Peripheral blood mononuclear cells (PBMC) or purified subsets of lymphocytes were stimulated with sonicated extracts of P. gingivalis for 24 hours. Cells were harvested and monitored for expression of CD69 by flow cytometry. Cytokine production (IL-10, IL-12, and IL-15) in P. gingivalis-stimulated PBMC cultures was measured by ELISA. To identify IL-10 producer cells, a cell depletion experiment was used and confirmed by the ability of the purified cell population to produce IL-10. To evaluate the effect of P. gingivalis and IL-10, the proliferative response of purified B cells was assessed by [3H] thymidine uptake.

RESULTS

PBMC cultured with P. gingivalis led to a large number of activated B and natural killer (NK) cells as monitored by CD69 expression. When positively sorted cells were used, the bacterium itself could directly activate only B cells but not NK cells, alphabeta, and gammadelta T cells. Measurement of B-cell regulatory cytokine production in P. gingivalis-stimulated PBMC cultures revealed a large amount of IL-10 but no detectable IL-12 or IL-15; the major producing cells were monocytes, not B cells or alphabeta T cells. When IL-10 was added to B cells in the presence of bacteria, significantly increased B-cell proliferative responses were observed.

CONCLUSIONS

These results suggest that P. gingivalis, both directly and indirectly via macrophage IL-10, may play an important role in polyclonal B-cell activation associated with periodontal disease.

Polyclonal B cell activators and in vitro induction of auto-antibody reactive with collagen

Cells producing autoantibodies are known to be present in chronically inflamed periodontal tissues. In sites of chronic inflammation, polyclonal B cell activators (PBA) are known to exhibit adjuvant activity when combined with foreign antigens. These results prompted an examination of PBA in eliciting an antibody response to an autoantigen (i.e. collagen type I). Rat lymphocytes were stimulated with rat collagen (type I), microbial PBA (LPS) or the combination of LPS plus rat collagen in vitro. Anti-collagen antibody-forming cells (AFC) were enumerated using an ELISPOT assay. Collagen or LPS alone elicited few anti-collagen AFC but the addition of LPS to collagen resulted in a substantial adjuvant effect and yielded maximal responses to collagen. Comparisons of anti-collagen AFC from short-term immunized (2-6 wk after booster), non-immunized and long-term immunized (3-4 months after booster) animals were performed. It revealed that cells from recently immunized rats were significantly easier to activate than the other 2 groups. The adjuvant effect of microbial PBA may be important in anti-collagen antibody production and thus the localization of PBA in periodontal pockets may explain why anti-collagen AFC are restricted to the chronically inflamed periodontal tissues.

Studies of proliferative responses by long-term-cryopreserved peripheral blood mononuclear cells to bacterial components associated with periodontitis

Freezing techniques provide a means for repeating and extending immunological assays with frozen aliquots of an individual's peripheral blood mononuclear cell fraction. Lymphocytes which are stored frozen for a limited time retain their ability to respond to polyclonal B-cell activators, mitogens, and antigens of dental interest. Our studies extend these previous findings by determining lymphocyte functional activity following frozen storage for up to 100 weeks. In addition, the autologous immune response was measured by spontaneous lymphocyte proliferation following 0, 1, 40, and 60 weeks of frozen storage. Peak responses for all individuals occurred at day 7 of incubation. The lymphocyte proliferative response to the superantigens toxic shock syndrome toxin-1 (TSST-1) and Staphylococcus enterotoxin A (SEA) were not changed after 100 weeks of frozen storage. Maximum responses varied among the individuals but occurred at equivalent stimulator concentrations. However, slopes generated from data obtained following 0, 4, 13, 20, 30, 50, 88, and 100 weeks of frozen storage showed no significant deviation from zero (P > 0.05) for all individuals tested. After 100 weeks of storage, the total changes in proliferative activity (counts per minute per week) were -2.1% +/- 16.8% and -5.5% +/- 17.0% for TSST-1 and SEA, respectively. The lymphocyte proliferative responses to pokeweed mitogen, concanavalin A, and sonicates of two periodontal pathogens (Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans) following frozen storage were similar to those with TSST-1 and SEA. These results indicate that peripheral blood mononuclear cells stored frozen may serve as appropriate controls to monitor changes in the disease state long-term periodontal treatment.

Taxonomy, biology, and periodontal aspects of Fusobacterium nucleatum

The pathogenic potential of Fusobacterium nucleatum and its significance in the development of periodontal diseases, as well as in infections in other organs, have gained new interest for several reasons. First, this bacterium has the potential to be pathogenic because of its number and frequency in periodontal lesions, its production of tissue irritants, its synergism with other bacteria in mixed infections, and its ability to form aggregates with other suspected pathogens in periodontal disease and thus act as a bridge between early and late colonizers on the tooth surface. Second, of the microbial species that are statistically associated with periodontal disease, F. nucleatum is the most common in clinical infections of other body sites. Third, during the past few years, new techniques have made it possible to obtain more information about F. nucleatum on the genetic level, thereby also gaining better knowledge of the structure and functions of the outer membrane proteins (OMPs). OMPs are of great interest with respect to coaggregation, cell nutrition, and antibiotic susceptibility. This review covers what is known to date about F. nucleatum in general, such as taxonomy and biology, with special emphasis on its pathogenic potential. Its possible relationship to other periodontal bacteria in the development of periodontal diseases and the possible roles played by OMPs are considered.

Taxonomy, biology, and periodontal aspects of Fusobacterium nucleatum

The pathogenic potential of Fusobacterium nucleatum and its significance in the development of periodontal diseases, as well as in infections in other organs, have gained new interest for several reasons. First, this bacterium has the potential to be pathogenic because of its number and frequency in periodontal lesions, its production of tissue irritants, its synergism with other bacteria in mixed infections, and its ability to form aggregates with other suspected pathogens in periodontal disease and thus act as a bridge between early and late colonizers on the tooth surface. Second, of the microbial species that are statistically associated with periodontal disease, F. nucleatum is the most common in clinical infections of other body sites. Third, during the past few years, new techniques have made it possible to obtain more information about F. nucleatum on the genetic level, thereby also gaining better knowledge of the structure and functions of the outer membrane proteins (OMPs). OMPs are of great interest with respect to coaggregation, cell nutrition, and antibiotic susceptibility. This review covers what is known to date about F. nucleatum in general, such as taxonomy and biology, with special emphasis on its pathogenic potential. Its possible relationship to other periodontal bacteria in the development of periodontal diseases and the possible roles played by OMPs are considered.

Comparative virulence of periodontopathogens in a mouse abscess model

OBJECTIVE(S)

This report compares the virulence of selected strains of P. gingivalis, A. actinomycetemcomitans, C. rectus, F. nucleatum and T. denticola in a murine model as a measure of pathogenic potential of these oral microorganisms. The characteristics of the tissue destruction associated with these monoinfections were then related to a potential model for bacterial synergism in progressing periodontitis.

DESIGN AND METHODS

All bacterial strains were grown to mid-logarithmic to early stationary growth phase, harvested and used at various doses to challenge BALB/c normal and BALB/c dexamethasone (DEX) treated mice to mimic a neutrophil dysfunction. The characteristics of tissue destruction, and overt tissue destructive capacity of these species were examined as a function of challenge dose and time.

OUTCOME MEASURES

The mice were examined for an interval of approximately 15 days post-challenge and the presence/absence of lesions, localized or generalized nature of the lesion (including size in mm2), and lethality of the infection were assessed.

RESULTS

Comparison of the virulence of the various P. gingivalis strains related to lethality and lesion size associated with destruction of the connective tissue, indicated a virulence capacity of P. gingivalis strains 53977>W50 = T22>3079>33277>381. C. rectus elicited localized necrotic lesions which were limited to the epithelial layers of the skin. The size of the lesions also indicated a graded difference in virulence, such that C. rectus strains 234>576>>33238. A. actinomycetemcomitans caused the formation of classic localized abscesses with a PMN infiltrate and inflammatory exudates. Although each of the A. actinomycetemcomitans strains exhibited a similar virulence pattern in this murine model, A. actinomycetemcomitans serotype b representative strains were potentially more pathogenic with a virulence capacity of 3113D-N = 3975A>JP2 > or = Y4>29523>33384. Both C. rectus and A. actinomycetemcomitans strains showed clear evidence that recent clinical isolates were more virulent than laboratory strains. Challenge with F. nucleatum resulted in tissue destructive responses which were different from those observed with the other strains used in this study. A rapid onset of dose-dependent lesion development, related to the formation of either closed abscesses or open lesions, was observed with F. nucleatum. Tissue involvement was also greater at lower F. nucleatum doses when compared to the other bacteria. F. nucleatum challenge of DEX-treated mice resulted in a shift to open lesions. T. denticola appeared to be more tissue invasive than the other species examined in this study. Challenge of mice with T. denticola resulted in involvement of multiple tissues, including epithelial and connective tissues, as well as appearing to invade muscle layers and deeper tissues. In addition to invading deeper tissues, the resulting lesions took considerably longer to resolve. In the DEX-treated mice (neutrophil depleted), P. gingivalis, C. rectus, and A. actinomycetemcomitans were significantly more virulent. In contrast, while DEX treatment altered the characteristics of lesions caused by F. nucleatum, the extent of lesions produced by F. nucleatum and T. denticola was not substantially enhanced.

CONCLUSIONS

The results obtained from this study suggest that different microorganisms have the ability to provide individual pathologies which may act in an additive/synergistic fashion contributing to the tissue destruction noted in periodontitis.

Prostaglandin E2 regulates gingival mononuclear cell immunoglobulin production

Histological studies have revealed elevated levels of T and B lymphocytes in inflamed gingival tissue. Functional analysis of these B cells has determined that they are spontaneously secreting large amounts of immunoglobulin. Several components of bacterial plaque which accumulate during the onset of periodontal disease induce polyclonal B cell activation, and are most likely responsible for the "hyperactive" state of these gingival B lymphocytes. In addition to this exaggerated humoral response, increased levels of inflammatory mediators, such as prostaglandin (PG) E2, have been implicated in the pathogenesis of disease. Therefore, the purpose of this study was to determine if PGE2 could regulate immunoglobulin production within inflamed gingival tissue. Specimens were harvested during routine surgery of patients with chronic adult periodontitis. Utilizing an ELISA, elevated levels of IgG were detected in the supernatant of cultured gingival mononuclear cells. Inclusion of indomethacin, which inhibits arachidonic acid metabolites such as PGE2, caused a decrease in IgG levels. PGE2 exerted a biphasic effect upon IgG production, with high doses diminishing and low doses increasing IgG levels. From a clinical perspective, these results suggest that elevated levels of PGE2 associated with inflammation will attenuate an IgG response and, as PGE2 production wanes, the local humoral response will rebound. Interestingly, the combination of low dose PGE2 and IL-4 induced a synergistic rise in IgG production. These findings support the theory that local PGE2 levels can regulate immunoglobulin production and potentiate cytokine induced class switching within gingival tissue.

Physiopathology of primary periodontitis associated with plaque. Microbial and host factors. A review. Part 1

Microbial factors involved in the genesis of periodontitis include colonization, bacterial penetration of the epithelium, multiplication and invasive-destructive capacity. Colonization of the gingival sulcus is related, to a certain extent, to supragingival plaque. Bacterial multiplication is induced by nutrients in the gingival fluid, and nutrients produced by degradative and excretory microbial activity. Invasion and destruction are mediated by exotoxins, structural elements of the bacteria, enzymes, metabolites, polyclonal lymphocyte activity, fibroblastic cytotoxicity, and leukocyte chemotactic inhibition.

Specific immune response to the 40-kDa outer-membrane protein of Porphyromonas gingivalis in mice

Whether B-cell activation to Porphyromonas gingivalis in periodontal diseases is the consequence of a specific immune response or is due to non-specific polyclonal activation is still not clear. Here the immune response of mice to a purified 40-kDa recombinant protein antigen, a major outer-membrane protein specific to P. gingivalis, was investigated. Patients' sera strongly reacted to this recombinant antigen. Purified splenic T and B cells from mice immunized with 40-kDa antigen or from normal mice were reconstituted in vitro and cultured in the presence or absence of the P. gingivalis 40-kDa protein antigen and antigen-presenting cells (APCs). In vitro antibody production to this particular antigen was analysed with respect to the requirement of helper T cells and APCs by enzyme-linked immunosorbent assay. The results clearly showed that an effective secondary response required the presence of B cells, T cells and APCs. In the absence of CD4+ helper T cells, an antibody response to the 40-kDa protein was not observed. In addition, the requirement of H-2 restricted, Ia-positive APCs was evident for an adequate response to the 40-kDa protein of P. gingivalis. Thus the antibody response to the 40-kDa protein of P. gingivalis was generated in an immunologically antigen-specific manner and was not simply the result of polyclonal B-cell activation. This in vitro system could be used in the detection of antigen-specific memory B or T cells in patients with periodontal diseases.

Serum and gingival crevicular fluid anti-desmosomal antibodies in periodontitis

SDS polyacrylamide gel electrophoresis separates desmosomal proteins and glycoproteins of bovine tongue epithelium by their relative molecular mass. The Western immunoblot technique was used to reveal the reactions of desmosomal proteins and glycoproteins with naturally occurring antibodies in serum and gingival crevicular fluid (GCF). Naturally-occurring serum and GCF antibodies (IgG and IgM) from periodontitis patients and healthy, unaffected controls reacted with desmosomal proteins (desmoplakins) and glycoproteins (desmogleins). Sera from 90% of subjects with periodontitis showed increased reactions of IgG with desmoplakins (240 and 210 kDa) and 80% with desmogleins (165, 130, and 115 kDa), when compared with unaffected controls. Patients' IgG reacted with desmosomal components more strongly than IgM. IgG antibodies against desmosomal antigens in GCF showed similar specificities from patients and healthy subjects and to their serums. When GCF within individuals with periodontitis was compared, anti-desmosomal IgG from diseased sites showed greater reactivity than healthy controls. These data suggest that anti-desmosomal antibodies are a normal part of the immune repertoire. The presence of elevated titers of anti-desmosomal antibodies appear to distinguish periodontitis from unaffected sites. When detected, elevated titers of anti-desmosomal antibodies may contribute to the pathogenesis and indicate increased risk of periodontitis.

Different responses in B cells induced by Porphyromonas gingivalis and Fusobacterium nucleatum

A phenotypic study had shown that gingival B cells respond differently to two periodontopathic bacteria, Porphyromonas gingivalis and Fusobacterium nucleatum. Further investigation now shows a reduction in the percentage of Ki-67 + T cells in cultures of gingival and peripheral blood mononuclear cells stimulated with P. gingivalis for 3 and 6 days, respectively, but no suppression of Ki-67 expression in B cells in response to either P. gingivalis or F. nucleatum. Depletion studies of cultures of peripheral blood mononuclear cells showed that in the absence of CD4 cells, the percentage of CD19+ and CD20+ B cells stimulated with P. gingivalis increased after 6 days whereas depletion of CD8 cells resulted in a rise in the percentage of F. nucleatum- and P. gingivalis-stimulated B cells, although this was not significant in the case of P. gingivalis. Specific antibody to P. gingivalis and F. nucleatum was found in culture supernatants of gingival but not of peripheral blood mononuclear cells, indicating a possible higher frequency of antigen-specific B cells in periodontal lesions. IgG was the predominant isotype in both gingival and control peripheral blood cultures, followed closely by IgA in gingival cultures. F. nucleatum stimulated higher levels of Ig in cultures of peripheral blood mononuclear cells than P. gingivalis or cells cultured in medium only, whereas in gingival cell cultures, stimulation by P. gingivalis appeared to result in higher levels of IgG. Also Ig was present at day 3 in gingival cultures, whereas in the blood cell cultures, Ig was only detected at day 6, further suggesting a degree of activation of of gingival B cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Serum antibody responses in human periodontitis to cellular components of Capnocytophaga

Serum levels of IgM, IgG and IgG-antibody subclasses directed against cell envelopes, lipopolysaccharides and cytoplasmic fractions from Capnocytophaga sputigena, C. gingivalis and C. ochracea were examined in age-, race- and sex-matched periodontally healthy (n = 25) subjects and subjects with adult periodontitis (n = 25). The envelopes and cytoplasmic fractions were obtained by ballistic disintegration of the cells and ultracentrifugation. Cell envelopes were treated with DNase, RNase and lysozyme. Lipopolysaccharides were obtained by hot phenol-water extraction and treated with DNase and RNase. The relative levels of the antibodies in response to the cell fractions were measured by the streptavidinbiotin micro enzyme-linked immunosorbent assay. Both groups showed IgM and IgG antibodies to each fraction of the three Capnocytophaga species, but the frequency of positive IgG subclass responses varied. The IgG4 responses were lower than the other subclasses. There were no significant differences between the IgM antibody levels of the two groups. However, the adult periodontitis group had significantly lower IgG antibody titres to the cell envelopes and cytoplasmic fractions of C. gingivalis and C. ochracea, and lipopolysaccharide of C. gingivalis. These results were reflected in the depressed levels of IgG1 and/or IgG2 to these cellular fractions from the same bacterial species. The adult periodontitis group also showed a lower level of IgG1 to the cytoplasmic fractions of C. sputigena without any depression in the total IgG antibody level. There were no significant differences between the groups in IgG3 and IgG4 antibody levels to any of the cellular fractions.(ABSTRACT TRUNCATED AT 250 WORDS)

In situ characterization of mononuclear cells in marginal periodontitis of patients with Down's syndrome

An indirect immunofluorescence technique on cryostat sections was used to study the cellular composition in chronic marginal periodontitis (CMP) of patients with Down's syndrome (DS). The findings were compared with CMP lesions in otherwise normal patients (NP). The distribution and amount of CD22+ cells (B lymphocytes), CD3+ cells (pan T lymphocytes), CD4+ cells (helper T subset), CD8+ cells (suppressor/cytotoxic T subset), and CD11c+ cells (in tissue, mainly monocytes and macrophages) were investigated. Morphologic studies showed a denser inflammatory infiltrate in DS than in NP. Countings showed significant differences in cell distribution (p = 0.0003) and cell profiles (p = 0.0273) between the two groups. The median CD4+/CD8+ ratio in DS (2.73) was significantly higher (p = 0.0024) than found in gingival inflammatory lesions from NP (1.08). The present study shows that DS patients have a different, more pronounced, immune response in CMP than NP.

Isolation and characterization of enzymes hydrolyzing chymotrypsin synthetic substrate (Enzyme I) and trypsin synthetic substrate (Enzyme II) from the envelope of Capnocytophaga gingivalis

Enzymes hydrolyzing chymotrypsin synthetic substrate and trypsin synthetic substrate, referred to as Enzyme I and Enzyme II, respectively, were found in the envelope fraction of Capnocytophaga gingivalis (ATCC 33624). Detergent extraction of both enzymes were purified by gel filtration, ion exchange chromatography, and affinity chromatography. The Enzyme I was a serine-containing metallo enzyme with a molecular mass of 77 kDa. The molecular mass of the Enzyme II was 83 kDa, and it was inhibited by tosyl-L-lysine chloromethyl ketone and leupeptin, and thus may be related to trypsin.

Immunity to self-antigens in periodontal disease

Auto-antibody to collagen, previously detected in periodontal disease, may represent either a response to local tissue damage or be the manifestation of a disturbance of the host immune response induced by the periodontal flora and its products. In an effort to distinguish between these two hypotheses, this study was undertaken to determine circulating IgG auto-antibody levels in 41 periodontal-disease patients against 12 self-antigens (salmon DS-DNA, calf SS-DNA, human and bovine thyroglobulin, rabbit proteoglycan, horse myoglobin, bovine myosin, actin, fetuin, human transferrin, cytochrome C, and human Type I collagen) and compare them to those in 21 periodontal disease-free subjects. None of the detected IgG auto-antibody levels were significantly different between periodontal disease and control sera (Mann-Whitney U-test, P greater than 0.05) except for human Type I collagen (P less than 0.05). Fifty-six percent of patients and 38% of controls were "broad responders;" i.e., 50% or more of the auto-antibody levels were higher than the median values of the control group; however, these values were not significantly different using the chi-square test. It was concluded that the destruction of connective tissue components is the primary driving force in the induction of the enhanced auto-antibody response found in periodontal disease. This response is apparently secondary to the primary bacterial infection which remains the major etiologic event.

Autoimmunity to collagen in adult periodontal disease: immunoglobulin classes in sera and tissue

The immunoglobulin class distribution of antibody to human collagen type I has been examined in sera and gingival extracts from patients with adult chronic periodontitis. Tissue extracts were made either by simple washing or ultrasonication. With either method, IgG and IgA antibodies to collagen were present in higher concentration in tissue extracts than in autologous serum when adjustment was made for dilution differences. No significant differences were found for IgM antibodies. Antibodies to human collagen type I are usually "natural antibodies" of the IgM class and, therefore, our findings suggest a class switch to IgG in inflamed gingivae, presumably due to prolonged antigenic stimulation.

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.

Accumulation of plasma cells in inflamed sites: effects of antigen, nonspecific microbial activators, and chronic inflammation

Plasma cells are common in chronically inflamed sites, including periodontal lesions. The aim of this study was to determine which factors contribute to this local accumulation of plasma cells. Specifically, we sought to evaluate the effects of specific antigen and nonspecific activators from an infectious agent associated with chronic inflammation (Fusobacterium nucleatum, an organism prominent in chronic periodontal lesions) and the effect of the chronic inflammation itself. Chronic inflammation (14 to 17 days) was induced in horseradish peroxidase (HRP)-immune rabbits by subcutaneous injection of 50 microliters of sterile alum in several sites in their backs. Controls included sites injected with saline or more acute sites examined after 3 days of alum inflammation. Sites were challenged with HRP (the antigen), sonicated F. nucleatum (the nonspecific activator), or both together to see whether F. nucleatum has an adjuvant effect. Three days after challenge, HRP-specific antibody-forming cells (AFC) were enumerated after peroxidase histochemistry. In noninflamed sites or sites with acute inflammation, virtually no HRP-specific AFC were evident. In contrast, chronic inflammation alone was sufficient to elicit a specific AFC response (congruent to 10 cells per mm2). Addition of either F. nucleatum or HRP to the chronic lesion about doubled the number of HRP-specific AFC. However, a dramatic 8- to 15-fold (80 to 150/mm2) increase was seen in chronically inflamed sites challenged with antigen and activator together. Interestingly, the activator did not have this adjuvant effect in the acute sites or in normal skin. In short, accumulation of plasma cells in inflamed sites is promoted by chronic inflammation, activators of microbial origin, and specific antigen. This milieu can be expected to develop in some periodontal lesions and could help explain why gingival crevicular fluid from some sites may contain extraordinary levels of locally produced specific antibodies for certain antigens.

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.

Analysis of in vitro lymphoproliferative responses and antibody formation following subcutaneous injection of Actinobacillus actinomycetemcomitans and Wolinella recta in a murine model

The potential of Wolinella recta and Actinobacillus actinomycetemcomitans to cause abscesses and induce an immune response was tested in BALB/c mice. Mice were injected subcutaneously with W. recta, A. actinomycetemcomitans or a mixture of these 2 microorganisms. Mice injected with A. actinomycetemcomitans alone, or with both organisms, demonstrated abscesses at the injection site 2 days later, from which pure cultures of A. actinomycetemcomitans were isolated. Mice injected with W. recta had small, flat abscesses at the injection site from which no bacteria could be cultured. W. recta was cultured from injection sites only when associated with A. actinomycetemcomitans. Mice developed positive serum IgG antibody responses to W. recta by 20 days post-injection but not to A. actinomycetemcomitans whether injected in pure culture or mixed infection. In vitro lymphoproliferative responses following injection of W. recta and/or A. actinomycetemcomitans resulted in increased lymphocyte reactivity in unstimulated cultures and decreased in vitro responses to phytohemagglutinin. In vitro lymphoproliferative responses to Escherichia coli LPS or Salmonella typhimurium LPS were depressed in mice injected with A. actinomycetemcomitans, but not in mice injected with W. recta.

Biochemical comparison of proteolytic enzymes present in rough- and smooth-surfaced capnocytophagas isolated from the subgingival plaque of periodontitis patients

Four rough-surfaced (R) and three smooth-surfaced (S) clinical isolates of Capnocytophaga obtained from the subgingival plaque of periodontitis patients were studied for their peptidase and protease profiles. The results were compared with those obtained with C. gingivalis (which has a smooth morphology). All cell extracts obtained by ultrasonic treatment displayed high peptidase activity toward N-aminoacyl-2-naphthylamines, the best substrates being the arginyl, aspartyl, and leucyl derivatives. The R and S isolates did not differ in these enzyme activities. Also the protease profiles studies with 4-phenylazobenzyloxycarbonyl-L-prolyl-L-leucylglycyl-L-proly l-D-arginine (PZ-PLPGA) and casein were similar. All extracts also hydrolyzed furylacryloyl-L-leucylglycyl-L-prolyl-L-alanine (FALGPA), reconstituted type I [3H]-collagen, and gelatin. N alpha-Benzoyl-DL-rginyl-2-naphthylamine was hydrolyzed faster by the R than the S strains. Comparison between cell suspensions and cell extracts of C. gingivalis showed the suspensions to be enzymatically more active than the extracts. In general, peptidase substrates and PZ-PLGPA were hydrolyzed at a higher rate by suspensions than by extracts, while protease substrates (such as casein) were hydrolyzed faster by the extracts. Gelatin and FALGPA were hydrolyzed by cell extracts only. Fast protein liquid chromatography of peptidases on a gel column was found to be a suitable method to differentiate between R and S isolates in diagnostics, while the chromatographic profiles of proteases were not suitable for this purpose.

Interaction of Fusobacterium nucleatum 191 with human peripheral blood lymphocytes

Fusobacterium nucleatum is frequently isolated in high numbers from the subgingival plaque of patients with periodontal diseases. Adherence of these bacteria to several host tissues is lectin-like in that it is inhibited by galactose, lactose, and N-acetyl-galactosamine. Since F. nucleatum has the capacity to activate human peripheral blood lymphocytes, the purpose of this study was to determine whether F. nucleatum adheres to lymphocytes and, if so, to determine whether lectin-like interactions facilitate lymphocyte activation. Adherence of F. nucleatum strain 191 to lymphocytes was confirmed by agglutination assays, scanning electron microscopy, and by using fluorescein- or [3H]-labeled bacteria. Saturation of adherence was reached at about 35 bacteria per lymphocyte. F. nucleatum adhered to greater than 90% of the lymphocytes, and adhered in higher numbers to B cell-enriched subpopulations than to T cell-enriched subpopulations. Adherence was inhibited by N-acetyl-galactosamine, lactose greater than galactose, alpha- and beta-methyl galactoside, but not by 100 mM glucose, mannose, N-acetyl-glucosamine, or other sugars tested. Lymphocytes underwent mitogenesis when preincubated with bacteria and washed to remove weakly adherent and non-adherent bacteria. Mitogenesis induced by low concentrations of F. nucleatum was reduced, but not completely eliminated, by N-acetyl-galactosamine. However, N-acetyl-galactosamine had no effect on mitogenesis induced by preincubation with high concentrations of bacteria. These results suggest that adherence of F. nucleatum facilitates activation of lymphocytes, particularly at low concentrations of bacteria.

Serum antibodies and loss of periodontal bone in patients with rheumatoid arthritis

The number of teeth, % of alveolar bone loss, serum IgG, and serum antibodies to Bacteroides gingivalis, Capnocytophaga ochracea and Eubacterium saburreum were recorded in 37 patients diagnosed with rheumatoid arthritis (RA) and in an age- and sex-matched control group of 37 individuals free from RA. The RA group had a significantly increased loss of teeth and loss of alveolar bone compared to the control group. The RA patients also had a significantly increased level of serum IgG. In the total material, 26% of the variation in loss of alveolar bone was accounted for by age, diagnosis of rheumatoid arthritis, and levels of antibodies against B. gingivalis and E. saburreum. In the RA group, 48% of this variation was accounted for by age, total serum IgG and IgG antibodies to B. gingivalis and E. saburreum.

Stimulation of lymphocytes in vitro by Bacteroides intermedius and Bacteroides (Porphyromonas) gingivalis sonicates

The present study was designed to assess whether the in vitro stimulation of lymphocytes by sonicates of Bacteroides intermedius and Bacteroides (Porphyromonas) gingivalis is antigen specific or non-specific. In addition, the role of T and B lymphocytes in these responses was assessed. Peripheral blood lymphocytes obtained from healthy volunteers were cultured in the presence of these bacterial preparations and the proliferative response was measured. In similar experiments the response of umbilical cord blood lymphocytes did not exceed background values. In limiting dilution experiments only 1:4000, 1:6800, and 1:8200 of the lymphocytes initially reacted to B. intermedius, which strongly argues for the antigen-specificity of the response. Purified T cells, in the presence of monocytes, proliferated when stimulated with B. intermedius and B. gingivalis. As for B cell stimulation, the bacterial extracts were capable of inducing IgM production, which appeared to be T cell dependent. These findings support the notion that B. intermedius and B. gingivalis induce specific T cell activation; secondarily, a T cell dependent, polyclonal B cell activation may occur.

Some immunological findings in adult periodontitis

There is little doubt that immunological mechanisms play an important role in chronic inflammatory periodontal disease. At the same time, it is recognized that patient susceptibility is ultimately responsible for the clinical manifestation of the disease. In this context, the present study was undertaken to examine a range of systemic immunological parameters in patients with adult periodontitis (AP), so as to test the hypothesis that a specific pattern would identify diseased--possibly 'at risk'--patients. These parameters included serum IgA, IgG, IgM, IgD, C3, transferrin, the presence of circulating immune complexes, and the number of circulating T (E-rosette forming) cells. One hundred and forty AP patients and 70 healthy controls were examined. Following a complex statistical analysis only the levels of IgG, IgM and IgD were significantly increased in adult periodontitis (p less than 0.05) while an increase in circulatory immune complexes was significant only for separate statistical tests. Although statistically different, the levels seen in AP patients were still within the normal range hence the clinical significance of the findings is such that it is unlikely that these systemic immunological parameters per se do define an 'at risk' population.

Polyclonal B-cell activation in periodontitis

The evidence that periodontitis-associated bacteria contain potent PBA factors is very strong. Clearly, antibodies directed against non-oral antigens are produced in the inflamed periodontal lesion, and PBA appears to contribute to that production. It is also clear that B cells and plasma cells are the major cell types in the periodontal lesion. Furthermore, alterations in the regulation of B-cell responses to PBA factors are associated with severe periodontal disease. However, evidence demonstrating that activated B cells and plasma cells are directly involved in the pathogenic mechanisms leading to destruction of the periodontal support is still circumstantial. Polyclonal B-cell activation and potential pathways by which PBA-stimulated cells could be involved in periodontal destruction remain largely hypothetical. It appears that IL-1 is an important osteoclast-activating agent, and that LPS, which is a potent PBA factor in many systems, can elicit IL-1 production by B cells as well as by the monocyte/macrophage lineage. Recent data indicating that IL-1 is produced by numerous malignant B-cell lines lend support for the idea that B-cell IL-1 could be important in bone resorption. It is also likely that polyclonal activation may lead to production of autoantibody such as anti-type I and anti-type III collagens, and the destruction of self tissues through ADCC reactions, immune complex formation, and complement activation. Further research is needed to determine how the B cell/plasma cell may participate in tissue injury in periodontitis, and how the B-cell response to PBA factors is regulated.

Abnormal lymphocyte profiles and leukotriene B4 status in a patient with Crohn's disease and severe periodontitis

THIS CASE REPORT DESCRIBES clinical and laboratory findings for a 60-year-old woman with recently diagnosed Crohn's disease and severe generalized periodontitis. Comparison of dental radiographs taken in 1975, in 1983, and at the time of our evaluation in 1986 revealed dramatic progression of alveolar bone loss over that period. Standard laboratory blood tests did not reveal any remarkable significant leukocyte abnormalities, but flow cytometric analysis of lymphocytes revealed a paucity of B cells stained with anti-light chain antibodies, and an increased proportion of T lymphocytes which were dully-stained with anti-CD5 monoclonal antibody. B cell function as determined by in vitro proliferative responsiveness to anti-IgM antibody was only about 50% of that observed with cells from two healthy normal subjects. Serum leukotriene B4 (LTB4) was elevated to 150% of normal values, in spite of the fact that the patient was taking a systemic anti-inflammatory drug which is known to reduce LTB4 levels. The microbial flora was highly mixed and included several putative periodontopathic bacteria. Therapy consisted of oral hygiene instruction, scaling and root planing, mucoperiosteal-flap curettage, extracoronal splinting, and selective extraction of three teeth. The periodontal status improved markedly with therapy. Possible relationships between the patient's immunological status, her Crohn's disease, and the severe periodontal breakdown are discussed.

Characterization and immunobiologic activities of lipopolysaccharides from periodontal bacteria

Bacterial surface structures play a critical role in the initiation of infectious diseases. Various surface components of pathogenic bacteria have been reported to be involved in host injury. There is a great deal of evidence incriminating certain Gram-negative, anaerobic bacteria present in the gingival crevice as etiologic agents of human periodontal diseases. We have isolated endotoxic cellular components from suspected periodontopathic bacteria and examined their immunobiological activities. Lipopolysaccharides (LPS) and lipid-associated proteoglycans (LPG) were prepared from whole cells by the phenol-water and butanol-water procedures, respectively. LPS from Bacteroides gingivalis, B. intermedius, B. oralis, and B. loescheii, Fusobacterium nucleatum and F. necrophorum, and Actinobacillus (Haemophilus) actinomycetemcomitans were found to possess biological activities comparable with those of LPS from E. coli K235 in terms of activation of Limulus lysate, B-cell mitogenicity, polyclonal B-cell activation, induction of bone resorption, and IL-1 production by macrophages. These LPS contained mainly sugars, amino sugars, and fatty acids. No heptose or 2-keto-3-deoxyoctonate (KDO) was detected in the Bacteroides LPS, while LPS from Actinobacillus and Fusobacterium species contained significant amounts of heptose as well as small quantities of KDO. Bacteroides LPS were clearly mitogenic for spleen cells of C3H/HeJ mice, which are non-responsive to LPS from E. coli, A. actinomycetemcomitans, and Fusobacterium species. Furthermore, polymyxin B was found to abrogate the mitogenic activity of LPS from E. coli, Actinobacillus, and Fusobacterium species, but not those from Bacteroides species. Spleen cells from both C3H/HeN and C3H/HeJ mice responded to all butanol-water-extracted LPG preparations, including those from E. coli, A. actinomycetemcomitans, and Fusobacterium species. It may be concluded that LPS and LPG isolated from suspected periodontopathic bacteria possess marked immunobiological potencies on lymphoreticular and bone cells.

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.

Antibody synthesis specific for nonoral antigens in inflamed gingiva

In vitro experimentation indicates that periodontitis-associated bacteria contain potent polyclonal B-cell activators (PBA). We reasoned that if PBA were operative in vivo, plasma cells specific for nonoral antigens should be present in the inflamed gingival tissues, which are characterized by a plasma cell infiltrate. To test this, rabbits with experimental periodontitis were immunized in the hind legs with the histochemically detectable antigen horseradish peroxidase (HRP) or glucose oxidase (GO). At various times after secondary immunization, inflamed gingival tissue was removed, sectioned, and treated histochemically to reveal plasma cells that specifically bound HRP or GO. Remarkably, by 9 days after secondary immunization, hundreds of HRP- or GO-binding plasma cells were found in the inflamed gingival tissue of immunized rabbits. The presence of these plasma cells, observed 7 to 10 days after booster immunization, was further substantiated by the presence of large amounts of locally produced HRP- or GO-specific antibody in gingival crevicular fluid. By 1 month after secondary immunization, the number of antigen-binding plasma cells had decreased dramatically, but a small number of antigen-specific plasma cells were detected for as long as 9 months after secondary immunization. The large number of HRP- or GO-specific plasma cells observed 9 days after immunization led us to see whether recently stimulated cells were more susceptible to PBA. Peripheral blood lymphocytes (PBL) were obtained at different times after booster immunization and cultured in the presence or absence of a PBA from Fusobacterium nucleatum. At 7 days after immunization, PBL spontaneously differentiated into antibody-forming cells in culture, and this process was enhanced by PBA. In contrast, PBL taken months after immunization produced little antibody in culture, and enhancement by PBA was difficult to detect. Compared with resting B cells, the recently stimulated B cells clearly differentiated more readily into antibody-forming cells. In conclusion, antibody synthesis specific for nonoral antigens did occur in inflamed gingival tissue, and a number of mechanisms, including PBA, probably contributed to this phenomenon.

Immunologic dysfunction in the pathogenesis of periodontal diseases

Despite significant progress in our understanding of the pathogenesis and etiology of periodontal diseases, the nature and contribution of the immune system to this disorder remains unclear. Several studies provide evidence for either a protective or destructive rôle. These conflicting findings are difficult to reconcile, since most interpretations tend to argue for a static contributory rôle (i.e., either protective or destructive) of the immune system. Current theories on the rôle of the immune response do not address these conflicting findings as well as the contradictory observation of a detectable immune response in the face of persistent infection in these patients. In this article, we present a model, based on available data, for the contribution of the immune system to the pathogenesis of periodontal disease. This model ascribes a dynamic rôle for the immune response. As documented in other infectious diseases, it is entirely possible, for example, that a state of immunologic dysfunction may occur in the earliest stages of periodontal disease progression; this may then be followed by a period of active immune reactivity (humoral and/or cellular) that would represent either a delayed or depressed response. This model is discussed in conjunction with recent findings that several suspected periodontal pathogens are capable of producing immunosuppressive agents. Many of the apparently contradictory clinical observations concerning the host immune response to oral pathogens and its correlation (or lack of) with both the progression and severity of periodontal disease may be accounted for in this model.