T cell responses of periodontal disease patients and healthy subjects to oral microorganisms

Inflammation indices in association with periodontitis and cancer

Inflammation is a complex physiological process that plays a pivotal role in many if not all pathological conditions, including infectious as well as inflammatory diseases, like periodontitis and autoimmune disorders. Inflammatory response to periodontal biofilms and tissue destruction in periodontitis is associated with the release of inflammatory mediators. Chronic inflammation can promote the development of cancer. Persistence of inflammatory mediators plays a crucial role in this process. Quantification and monitoring of the severity of inflammation in relation to cancer is essential. Periodontitis is mainly quantified based on the severity and extent of attachment loss and/or pocket probing depth, in addition with bleeding on probing. In recent years, studies started to investigate inflammation indices in association with periodontal diseases. To date, only few reviews have been published focusing on the relationship between blood cell count, inflammation indices, and periodontitis. This review presents a comprehensive overview of different systemic inflammation indices, their methods of measurement, and the clinical applications in relation to periodontitis and cancer. This review outlines the physiological basis of inflammation and the underlying cellular and molecular mechanisms of the parameters described. Key inflammation indices are commonly utilized in periodontology such as the neutrophil to lymphocyte ratio. Inflammation indices like the platelet to lymphocyte ratio, platelet distribution width, plateletcrit, red blood cell distribution width, lymphocyte to monocyte ratio, delta neutrophil index, and the systemic immune inflammation index are also used in hospital settings and will be discussed. The clinical roles and limitations, relationship to systemic diseases as well as their association to periodontitis and treatment response are described.

Roles of Porphyromonas gingivalis and its virulence factors in periodontitis

Periodontitis is an infection-driven inflammatory disease, which is characterized by gingival inflammation and bone loss. Periodontitis is associated with various systemic diseases, including cardiovascular, respiratory, musculoskeletal, and reproductive system related abnormalities. Recent theory attributes the pathogenesis of periodontitis to oral microbial dysbiosis, in which Porphyromonas gingivalis acts as a critical agent by disrupting host immune homeostasis. Lipopolysaccharide, proteases, fimbriae, and some other virulence factors are among the strategies exploited by P. gingivalis to promote the bacterial colonization and facilitate the outgrowth of the surrounding microbial community. Virulence factors promote the coaggregation of P. gingivalis with other bacteria and the formation of dental biofilm. These virulence factors also modulate a variety of host immune components and subvert the immune response to evade bacterial clearance or induce an inflammatory environment. In this chapter, our focus is to discuss the virulence factors of periodontal pathogens, especially P. gingivalis, and their roles in regulating immune responses during periodontitis progression.

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.

Characterization of T lymphocyte clones derived from Porphyromonas gingivalis infected subjects

Porphyromonas gingivalis plays a major role in the pathogenesis of periodontal disease, however some individuals with P. gingivalis infection do not experience periodontal breakdown. The aim of this study was to investigate the proliferative responses of two highly defined groups of subjects and to establish and characterize peripheral blood and gingival cell T cell lines and clones from subjects from these groups. The two groups were selected on the basis of P. gingivalis in their plaque and the presence of serum anti-P. gingivalis antibodies. Both groups therefore were seen to have P. gingivalis and to have responded to it. They however differed only in their clinical susceptibility (adult periodontitis) or resistance (gingivitis) to periodontal breakdown. Dose responses of peripheral blood mononuclear cells extracted from the subjects showed a trend towards a lower response by the adult periodontitis group to P. gingivalis outer membrane (OM) antigens. Peripheral blood T cell lines and clones responsive to P. gingivalis OM were established from a high responding gingivitis subject and a low responding adult periodontitis subject. Gingival T cell lines and clones were also derived from cells extracted from the periodontal tissues of the same periodontitis subject. The majority of T cells in the peripheral blood T cell line from the gingivitis subject were CD4 while those from the adult periodontitis subject were CD8. The gingival T cell line was CD3+ve CD4-ve and CD8-ve. All lines and clones proliferated slowly to P. gingivalis OM but phytohaemagglutinin (PHA) induced an increase in DNA synthesis in those derived from the gingivitis subject with little to no effect on those established from the adult periodontitis subject. Furthermore, PHA inhibited the proliferative response of the CD8 clone derived from the adult periodontitis subject. Phenotypic analysis demonstrated that all the peripheral blood clones expressed the alpha beta TCR while the gingival T cell clones expressed the gamma-delta TCR. All clones had the memory/primed CD45RO+ve phenotype and at least 80% of cells in each clone were HLA-DR+ve. A lower percent of gingival cells expressed CD45RA than the CD4 peripheral blood clones and the two CD8 clones also had a decreased CD45RA expression. The gingival T cell clones also expressed a low percent CD25 as did the CD8 clone derived from the adult periodontitis subject. The results suggest that clones derived from the gingivitis and adult periodontitis subject may be functionally different. The presence of gamma-delta T cells in adult periodontitis remains to be confirmed and their function determined.

Immunosuppressive factor from Actinobacillus actinomycetemcomitans down regulates cytokine production

A cytoplasmic soluble fraction of Actinobacillus actinomycetemcomitans Y4 was isolated and characterized as suppressing mitogen-stimulated proliferation of and cytokine production by C3H/HeN mouse splenic T cells. This factor, designated suppressive factor 1 (SF1), was isolated from the supernatant of sonicated whole bacteria and purified by Q-Sepharose Fast Flow column chromatography, DEAE-Sepharose Fast Flow column chromatography, hydroxyapatite high-pressure liquid chromatography (HPLC), and Protein Pack 300 & 125 gel filtration HPLC. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis revealed that the purified SF1 migrated as a single band corresponding to a molecular mass of 14 kDa. This molecule was protease labile, heat resistant, and noncytotoxic. N'-terminal sequence analysis revealed no homology with any known peptides of periodontopathic bacteria or with any host-derived growth factors. Purified SF1 suppressed the proliferation of mouse splenic T cells which had been stimulated with concanavalin A, as well as suppressing the production of interleukin-2 (IL-2), gamma interferon, IL-4, and IL-5 from CD4+ T cells as 0.1 microgram/ml or more. These data suggest that SF1 produced by the periodontal pathogen A. actinomycetemcomitans functions as a virulence factor by down regulating T-cell proliferation and cytokine production at local defense sites.

Reduction of infection-stimulated periapical bone resorption by the biological response modifier PGG glucan

Pulpal and periodontal diseases are bacterial infections which result in local connective tissue and bone destruction. Effective host resistance to these infections is primarily mediated by neutrophils and other phagocytic cells. PGG glucan (poly-beta 1-6-glucotriosyl-beta 1-3-glucopyranose glucan) is a biological response modifier which stimulates the production of neutrophils and upregulates their phagocytic and bactericidal activity. In the present studies, the effect of PGG glucan on infection-stimulated alveolar bone resorption was tested in an in vivo model. Periapical bone resorption was induced in Sprague-Dawley rats by surgical pulp exposure and subsequent infection from the oral environment. Animals were administered PGG glucan (0.5 mg/kg) or saline (control) subcutaneously the day before and on days 2, 4, 6, 9, 11, 13, 16, and 18 following the pulp exposure procedure. PGG glucan enhanced the number of circulating neutrophils and monocytes and increased neutrophil phagocytic activity approximately two-fold. PGG glucan-treated animals had significantly less infection-stimulated periapical bone resorption than control animals, as determined radiographically (-48.0%; p < 0.001) and by histomorphometry (-40.8% and -42.4% for first and second molars, respectively; p < 0.001). PGG glucan-treated animals also had less soft tissue destruction, as indicated by decreased pulpal necrosis. Only 3.3% of the first molar pulps from PGG glucan-treated animals exhibited complete necrosis, as compared with 40.6% of pulps from controls. Finally, PGG glucan had no effect on either PTH- or IL-1-stimulated bone resorption in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)

Adoptive transfer of suppressor T cells induced by Actinobacillus actinomycetemcomitans regulates immune response

Purified splenic T cells from C3H/HeN mice primed with immunosuppressive fraction (ISF) from A. actinomycetemcomitans were adoptively transferred to syngeneic mice with SRBC. The transfer of splenic T cells from mice, primed with various amounts of ISF for 6 days, resulted in the dose-dependent inhibition of IgM anti-sheep red blood cells (SRBC) plaque-forming cells (PFC) compared with normal and BSA-primed splenic T cells. Furthermore, the transfer of T cells from mice primed with 100 micrograms of ISF for 6 days to syngeneic and CD4-depleted mice caused the highest inhibition. Immune suppression did not depend on the B cell population in spleen from donor mice primed with ISF, nor on haplotypes as recipient. The immunosuppressive function of these ISF-primed T cells was abrogated by 1000 rad irradiation. Splenic T cells from ISF-treated mice could suppress the T cell-dependent proliferative responses of cocultured normal spleen cells in vitro. Analysis of T cell subsets of spleen cells from ISF-treated mice showed that the suppressor cell is susceptible to treatment with anti-CD8 and complement (C). ISF-sensitized suppressor T cells also suppressed secondary IgG anti-SRBC-PFC response after immunization with SRBC in vivo depending on sensitized periods induced by ISF. Treatment of T cells from mice which primed with ISF for 8 days, with goat anti-mouse CD8 antibody and C abrogated their suppressive effects, and secondary IgG response occurred. These results indicate that the adoptive transfer of ISF-induced T cells, which increased suppressor function, caused the perfect blocking of immune response, allowing promotion of secondary infection.

T cell proliferative responses to molecular fractions of periodontopathic bacteria

Soluble antigenic preparations of Veillonella parvula and Bacteroides gingivalis were separated by SDS-PAGE and used after electroblotting and solubilization for in vitro lymphocyte stimulation in 13 patients with severe periodontitis and 12 controls. The cellular responses of controls and patients to V. parvula antigens were represented by four main proliferation-inducing fractions with 74-66, 52-46, 22-19 and 12 kD mol. wt. These fractions induced slightly enhanced DNA synthesis in lymphocytes from eight patients who failed to respond to whole antigenic extract. Lymphocyte samples from Veillonella whole extract unresponsive patients were also examined for in vitro proliferation by B. gingivalis fractions. Almost all stimulatory activities could be classified into five regions of 84-74, 35-31, 28-25, 17-15 and 12 kD.

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.

Immunomodulatory effects of Bacteroides products on in vitro human lymphocyte functions

Bacteroides spp. have been implicated in the pathogenesis of several diseases, including periodontal diseases. In this study sonic extracts of 6 Bacteroides spp. were examined for their abilities to alter human lymphocyte function. We found that soluble extracts from Bacteroides intermedius, Bacteroides endodontalis, Bacteroides asaccharolyticus, Bacteroides melaninogenicus, and to a lesser degree Bacteroides loescheii, caused dose-dependent inhibition of human lymphocyte responsiveness to both mitogens and antigens. Suppression involved altered DNA, RNA and protein synthesis as well as immunoglobulin production. In contrast, Bacteroides gingivalis did not suppress these responses; instead, it stimulated lymphocyte proliferation and enhanced immunoglobulin production. It has been proposed that impaired host defense may play a pivotal role in the pathogenesis of many infections. The data presented in this paper suggest that microbial mediated immunosuppression may conceivably alter the nature and consequences of host-parasite interactions in periodontal disease.

Immunosuppressive properties of Actinobacillus actinomycetemcomitans leukotoxin

Actinobacillus actinomycetemcomitans produces a leukotoxin that kills human polymorphonuclear cells (PMNs) and monocytes but not lymphocytes. In this study, we examined A. actinomycetemcomitans leukotoxin for its ability to alter human peripheral blood lymphocyte (HPBL) responsiveness. After a 90-min exposure to the leukotoxin, all monocytes were killed and HPBL responsiveness to mitogens and antigens was significantly inhibited. The ability of the leukotoxin to inhibit HPBL responses was not surprising, since monocytes and macrophages are required for many lymphocyte functions. However, we were unable to totally restore HPBL responsiveness when adherent autologous monocytes were added back to cultures of leukotoxin-treated lymphocytes. These studies demonstrate that A. actinomycetemcomitans leukotoxin may also exert nonlethal effects directly on lymphocytes. Furthermore, impaired lymphocyte function did not appear to be the result of indirect effects of products released by dying monocytes. Although it is not clear how A. actinomycetemcomitans acts to cause disease, several investigators have proposed that impaired host defenses may play a pivotal role. Several studies have demonstrated defects in PMN, monocyte, and lymphocyte function in patients with periodontal disease. These findings, along with the data presented in this paper, support the hypothesis that patients who harbor A. actinomycetemcomitans could suffer from local or systemic immune suppression. The effects of this suppression may be to enhance the pathogenicity of A. actinomycetemcomitans itself or that of some other opportunistic organism.

Immunosuppressive effects of Centipeda periodontii: selective cytotoxicity for lymphocytes and monocytes

We have examined soluble sonic extracts prepared from several strains of Centipeda periodontii for their ability to alter human lymphocyte function. These organisms were isolated from subgingival plaque of patients with periodontal disease. We found that sonicates from several, but not all, strains of C. periodontii caused a dose-dependent inhibition of lymphocyte responsiveness to concanavalin A, phytohemagglutinin, pokeweed mitogen, and formalinized Staphylococcus aureus. Inhibition was associated with a concomitant decrease in cell viability assessed by trypan blue exclusion, 51Cr release, and electron microscopy. The maximal number of dead cells was observed 20 to 24 h after exposure to the sonic extract. Susceptible cells include human lymphocytes (both B and T), monocytes, and erythrocytes, whereas polymorphonuclear cells, murine L-929 fibroblasts, and sheep erythrocytes were not affected. Preliminary characterization of the cytotoxic activity indicates that it is heat labile and trypsin sensitive and has an Mr of 60,000. It has been proposed that impaired host defense may play a pivotal role in the pathogenesis of periodontal diseases. The data presented in this paper suggest that immunosuppression (local or systemic or both) could be initiated by C. periodontii. This immunosuppression may alter the nature and consequences of host-parasite interactions, thereby enhancing the pathogenicity of C. periodontii itself or some other opportunistic organism.

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.

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.

The stimulation of human peripheral blood lymphocytes by oral bacteria: macrophage and T-cell dependence

Human peripheral blood mononuclear lymphocytes from individuals with moderate periodontitis were separated into purified subpopulations of T lymphocytes and B lymphocytes by rosetting with sheep red blood cells (E). All three lymphocyte subpopulations were compared for proliferative responses to cell walls from seven oral bacteria, phytohemagglutinin (PHA), pokeweed mitogen (PWM), lipopolysaccharide (LPS), and streptolysin-O (SLO). Mononuclear cells and a re-combined subpopulation consisting of four parts purified T lymphocytes and one part B lymphocytes responded significantly to all of the stimulants. Purified T lymphocytes by themselves responded significantly to PHA and PWM, but were unresponsive to oral bacteria and SLO; however, T lymphocytes cultured with 2% autologous macrophages responded significantly to all seven oral bacterial cell walls and to SLO, which indicates that T-cell responses to oral bacteria are macrophage-dependent. T-cell-depleted non-E-rosette-forming B cells by themselves were poorly responsive to all of the tested stimulants; however, the responses of these cells to oral bacteria, PWM, LPS, and SLO increased significantly in the presence of 10% mitomycin-C-treated T cells, demonstrating that B cell proliferation to these stimulants is T-cell-dependent.

Host responses to bacteria and bacterial products in periodontal disease: immunosuppressive effects of periodontitis-related microorganisms?

Several recent investigations indicate that some patients with adult periodontitis have lowered serum antibody levels or reduced lymphoproliferative responses to certain periodontitis-related microorganisms. Many such patients tend to show increased responses after therapy. Some suggested mechanisms of such responses are reviewed and the possible significance of immunosuppressive effects of periodontitis-related microorganisms are briefly discussed.