Differences in Inflammation and Bone Resorption between Apical Granulomas, Radicular Cysts, and Dentigerous Cysts

INTRODUCTION

Dental cysts can be of inflammatory (radicular cysts) or noninflammatory (dentigerous cysts) origin. Apical periodontitis is a necrosis of the pulp and infection of the root canal causing the development of apical granulomas or radicular cysts. The immunology of granuloma and cyst formation is important because modern root filling materials are immunologically active and can contribute to the resolution of apical granulomas. In contrast, radicular cysts often require apicectomy. A better understanding of the pathophysiology of inflammation and bone resorption in apical periodontitis could be the basis for developing new root filling materials with superior immunomodulatory properties.

METHODS

Forty-one apical granulomas, 23 radicular cysts, and 23 dentigerous cysts were analyzed in this study. A tissue microarray of the 87 consecutive specimens was created, and human leukocyte antigen-DR isotype (HLA-DR)-, CD83-, receptor activator of nuclear factor kappa B ligand-, macrophage colony-stimulating factor (MCSF)-, galectin-3 (Gal3)-, CD4-, and CD8-positive cells were detected by immunohistochemistry. Tissue microarrays were digitized, and the expression of markers was quantitatively assessed.

RESULTS

HLA-DR, CD83, MCSF, and Gal3 expression was significantly (P < .05) higher in radicular cysts compared with apical granulomas. HLA-DR, CD83, MCSF, receptor activator of nuclear factor kappa B ligand, and Gal3 expression in dentigerous cysts was significantly (P < .05) lower than in both periapical lesions (apical granulomas and radicular cysts). CD4 and CD8 infiltration was not statistically different between apical granulomas and radicular cysts. Dentigerous cysts showed a significantly (P < .05) lower T-cell infiltration than apical periodontitis. The CD4/CD8 ratio was not significantly different between the analyzed groups.

CONCLUSIONS

The development of radicular cysts in apical periodontitis is associated with an increased expression of myeloid inflammatory markers and bone resorption parameters. Antigen-presenting cells and myeloid cells might be more relevant for the pathogenesis of apical periodontitis than T cells. Increased inflammation might promote the formation of radicular cysts and more pronounced bone resorption.

Cellular Profile and Expression of Immunologic Markers in Chronic Apical Periodontitis from HIV-infected Patients Undergoing Highly Active Antiretroviral Therapy

INTRODUCTION

This study tested the hypothesis that the inflammatory cell profile (CD3-, CD4-, CD8-, CD20-, and CD68-positive cells) and the expression of immunologic markers (tumor necrosis factor α, interferon-γ, interleukin-6, and interleukin-18) in chronic apical periodontitis are the same between non-HIV-infected patients and HIV-infected patients undergoing highly active antiretroviral therapy (HAART).

METHODS

Thirty-four surgically excised chronic apical periodontitis lesions were sampled from 34 patients (17 HIV-infected and 17 non-HIV-infected). The lesions were extracted from teeth with no previous endodontic treatment. All HIV-infected patients were undergoing HAART. The specimens were submitted to histopathologic and immunohistochemical analyses by using an optical microscope. Immunoexpression was graded into 2 levels, focal to weak and moderate to strong. The χ(2), Fisher exact, and Mann-Whitney tests were used to analyze all significant differences between groups.

RESULTS

Periapical cysts represented 70.6% and 52.9% of the lesions in the HIV-infected and non-HIV-infected groups, respectively; however, no statistically significant difference was observed (P = .481). There were no statistically significant differences between groups for the inflammatory cell profile and for any of the immunologic markers (P > .05).

CONCLUSIONS

There are no statistically significant differences of the cellular profile and expression of immunologic markers in chronic apical periodontitis between non-HIV-infected patients and HIV-infected patients undergoing HAART.

Evidence supporting a protective role for th9 and th22 cytokines in human and experimental periapical lesions

INTRODUCTION

The development of periapical granulomas is dependent on the host response and involves Th1, Th2, Th17, and Treg-related cytokines. The discovery of new Th9 and Th22 subsets, with important immunomodulatory roles mediated by interleukin (IL)-9 and IL-22, respectively, emphasizes the need for reevaluation of current cytokine paradigms in context of periapical lesions. We investigated the expression of IL-9 and IL-22 in active and stable human granulomas and throughout experimental lesion development in mice.

METHODS

Periapical granulomas (N = 83) and control specimens (N = 24) were evaluated regarding the expression of IL-9 and IL-22 via real-time polymerase chain reaction. Experimental periapical lesions were induced in mice (pulp exposure and bacterial inoculation) and the lesions evolution correlation with IL-9 and IL-22 expression kinetics was evaluated.

RESULTS

IL-9 and IL-22 mRNA expression was higher in periapical lesions than in control samples; higher levels of IL-9 and IL-22 were observed in inactive than in active lesions. In the experimental lesions model, increasing levels of IL-9 and IL-22 mRNA were detected in the lesions, and inverse correlations were found between IL-9 and IL-22 and the increase of lesion area in the different time point intervals.

CONCLUSIONS

Our results suggest that Th9 and Th22 pathways may contribute to human and experimental periapical lesion stability.

The potential role of suppressors of cytokine signaling in the attenuation of inflammatory reaction and alveolar bone loss associated with apical periodontitis

Inflammatory cytokines contribute to periapical tissue destruction. Their activity is potentially regulated by suppressors of cytokine signaling (SOCS), which downregulate signal transduction as part of an inhibitory feedback loop. We investigated the expression of the cytokines tumor necrosis factor alpha (TNF-alpha); interleukin (IL)-10 and RANKL; and SOCS-1, -2, and -3 by real-time polymerase chain reaction in 57 periapical granulomas and 38 healthy periapical tissues. Periapical granulomas exhibited significantly higher SOCS-1, -2, and -3, TNF-alpha, IL-10, and RANKL messenger RNA levels when compared with healthy controls. Significant positive correlations were found between SOCS1 and IL-10 and between SOCS3 and IL-10. Significant inverse correlations were observed between SOCS1 and TNF-alpha, SOCS1 and RANKL, and SOCS3 and TNF-alpha. Increased SOCS-1, -2, and -3 messenger RNA levels in periapical granulomas may be related to the downregulation of inflammatory cytokines in these lesions; therefore, SOCS molecules may play a role in the dynamics of periapical granulomas development.

Antigen-presenting cells in human radicular granulomas

Substantial numbers of dendritic cells have been detected in radicular granulomas. To test the hypothesis that local antigen presentation from dendritic cells to T-cells is involved critically in immunological responses within radicular granulomas, we compared characteristics of dendritic cells and macrophages by morphological and biological analyses. Under light microscopy, HLA-DR+ and CD68+ cells showed diverse profiles, including dendritic-shaped cells. Transmission electron microscopy revealed that HLA-DR+ dendritic cells, with long cytoplasmic processes and lacking distinct phagosomes, were concentrated in the lymphocyte-rich area. HLA-DR alpha-chain, CD83, and CD86 mRNAs from HLA-DR+ dendritic cells, and CD28 mRNA from CD28+ T-cells were up-regulated in lymphocyte-rich area. Scanning electron microscopy demonstrated that the density of gold particles on dendritic cells was higher than that on HLA-DR+ macrophages. These results suggest that dendritic cells in radicular granulomas are associated with local defense reactions as stronger antigen-presenting cells, as compared with macrophages.

Immunohistochemical detection of Langerhans cells in dental granulomas and radicular cysts

OBJECTIVE

Dental granulomas (DGs) and radicular cysts (RCs) are chronic periapical lesions frequently involving the jaws. Langerhans cells (LCs) are dendritic cells responsible for the presentation of antigens to T lymphocytes. This study examined the expression of LCs in DG and RCs by immunohistochemical staining.

STUDY DESIGN

Eighteen cases of DGs and 26 cases of RCs were analyzed using anti-CD1a marker.

RESULTS

CD1a-labeled LCs were observed in 11.1% of DGs and in 69.2% of RCs, showing a significant correlation (P < 0.0001; Fisher's test). In DGs, LCs were only observed in granulation tissue, showing discrete immunostaining density. In RCs, LCs exhibited both a round and a dendritic shape in all epithelial layers. Although a correlation was observed between immunostaining density and epithelial thickness, as well as between immunostaining and inflammatory intensity, the differences were not significant in radicular cysts.

CONCLUSION

Langerhans cells provide important insight into the immunopathogenesis of chronic periapical lesions.

Involvement of Inducible Nitric Oxide Synthase and Receptor for Advanced Glycation End Products in Periapical Granulomas

We examined the presence of the receptor for advanced glycation end products (RAGE) in periapical granulomas and analyzed the interaction between RAGE and inducible nitric oxide synthase (iNOS) to elucidate inflammatory reaction mechanisms. Periapical lesions were surgically removed from 37 patients with chronic periapical periodontitis and halved. Paraffin sections were prepared from half of each lesion and stained with hematoxylin and eosin, whereas cryostat sections were prepared from the other half. Based on the histological evaluation, 33 of the lesions were diagnosed as periapical granulomas. These were examined by immunohistochemistry using serial cryostat sections probed with anti-human iNOS or RAGE antibodies. Macrophages, lymphocytes, and endothelial cells expressed RAGE and these cell types, in addition to plasma cells, exhibited anti-iNOS immunoreactivity. Serial cryostat sections demonstrated the infiltration of RAGE-expressing cells around iNOS-producing cells, suggesting that these molecules may be important in the tissue injury associated with periapical periodontitis.

Human cytomegalovirus, Epstein-Barr virus and bone resorption-inducing cytokines in periapical lesions of deciduous teeth

BACKGROUND

A connection of herpesvirus periapical infection with symptomatic and large-size periapical lesions has been recognized in adult patients, but no data exist about a possible involvement of herpesviruses in severe periapical pathosis in children. Herpesviruses have the potential to elicit potent bone resorption-inducing cytokines in mammalian cells.

AIM

This study aimed to determine the occurrence of human cytomegalovirus and Epstein-Barr virus DNA, and mRNA transcripts of receptor activator of nuclear kappa B ligand (RANKL), osteoprotegerin, core binding factor alpha-1, colony stimulating factor-1, transforming growth factor-beta, and monocyte chemoattractant protein-1 in periapical symptomatic pathosis of deciduous teeth.

MATERIAL AND METHODS

Twelve deciduous molar teeth from patients aged 2-8 years were extracted due to severe periapical infection, and granulomatous tissue adherent to the root tip of the extracted teeth was collected using a surgical knife. Non-diseased pulpal tissue, obtained from 12 teeth extracted for orthodontic reasons, served as negative control. Polymerase chain reaction assays were employed to identify herpesvirus DNA and cytokine gene expression, using established polymerase chain reaction primers and procedures.

RESULTS

Seven (58%) of the periapical lesions yielded human cytomegalovirus and eight (67%) Epstein-Barr virus. Only one (8%) periapical lesion showed neither human cytomegalovirus nor Epstein-Barr virus. In healthy pulpal tissue, one (8%) specimen demonstrated human cytomegalovirus and another (8%) specimen revealed Epstein-Barr virus. Of the cytokines examined, RANKL expression showed significantly higher occurrence in periapical pathosis than in healthy pulpal tissue (P < 0.040). No relationship was identified between the type of herpesvirus and cytokine expression in the periapical lesions studied.

CONCLUSIONS

The present findings provide evidence of a putative role of human cytomegalovirus and Epstein-Barr virus in the pathogenesis of symptomatic periapical pathosis in deciduous teeth. Increased RANKL expression in periapical lesions may be of pathogenetic significance.

Differential expression of chemokines and chemokine receptors in inflammatory periapical diseases

BACKGROUND

Periapical lesions are thought to be the result of a local inflammatory response mediated by inflammatory cell infiltration and production of inflammatory mediators. Although chemokines are strongly implicated in the migration and activation of leukocytes in different inflammatory diseases and experimental models, little is known regarding the expression of chemokines and their receptors in human apical periodontitis.

OBJECTIVE AND METHODS

The objective of this study was to determine the expression of chemokines and their receptors by real-time polymerase chain reaction in samples obtained from healthy gingiva, periapical granulomas, and inflammatory periradicular cysts. The inflammatory infiltrate was characterized by immunohistochemistry.

RESULTS

Comparing cysts and granulomas, an increase in CD4+ and CD8+ cells was observed in granulomas, despite the similar numbers of CD45RO-positive cells detected in both lesions. The analysis of mRNA expression revealed increased levels of CCR1, CCR2, CCR3, CCR5, CXCR1, and CXCR3 in both types of lesion compared with controls. Cysts exhibited a higher expression of CCR3, CCR5, CXCR1, and CXCR3 compared to granulomas. A significantly higher expression of RANTES, IP-10, and MCP-1 was detected in cysts compared with controls or granulomas. The expression of interleukin-8, MIP-1alpha, and MIP-1beta was not different in the three experimental groups.

CONCLUSIONS

The increase in Th1 type (CCR1, CCR5, and CXCR3) and Th2 type (CCR2 and CCR3) receptors in both periapical lesions suggests the concomitant occurrence of Th1 and Th2 responses. Furthermore, the prevalent expression of the receptors CCR3, CCR5, CXCR1, and CXCR3 and of the chemokines RANTES, IP-10, and MCP-1 in cysts may point to a role in the progression of granulomas to cysts.

Immunological and ultrastructural characterization of plasma cells of human periapical chronic inflammatory lesions (granulomas)

Despite many studies on the topic, plasma cells found in human periapical chronic inflammatory lesions (granulomas) continue to present unresolved issues. In this study, we tried to assess quantitatively and qualitatively the nature of plasma cells of 4 human periapical granulomas. Samples were analyzed for relative amounts of IgG-, IgM-, IgA-, and IgE-positive plasma cells by immunohistochemistry, and for morphological changes by transmission electron microscopy (TEM). By immunohistochemistry, many plasma cells stained positively with anti-IgG and anti-IgM antibodies; fewer cells reacted with anti-IgE and anti-IgA. Russell Bodies, controversial aspects of plasma cell maturation, showed positive reactivity of the superficial layer only to antibodies against IgG and IgM. By TEM analysis, phenotypes of normal and dysfunctional plasma cells (Mott cells) were evident. Russell Bodies appeared as intra- or extracellular round vesicles, with an homogeneous internal core, and an external membrane, resembling rough endoplasmatic reticulum (RER). We can conclude that mucosal immune response is not the predominant type in the periapical lesions examined. Positive immunoreaction for IgG and IgM of Russell Bodies may be due to the residual RER membrane, whereas components of yet unidentified nature may occupy the internal core.

Presence of CXCR3-positive cells and IFN-gamma-producing cells in human periapical granulomas

In an attempt to understand further the balance between the types of helper T (Th) cells in human apical periodontitis, we examined the difference in the expression of the chemokine receptor and cytokine in samples obtained from human subjects by means of immunohistochemical methods. Chemokine receptor CXCR3-positive cells and IFN-gamma-producing cells were found to be present in human periapical granulomas, whereas chemokine receptor CCR3-positive cells and IL-4-producing cells could not be detected. By contrast, no factor expression was observed in a clinically healthy periodontal ligament serving as a negative control. Our findings suggest that Th1 cells may play an important role in the pathological process of local inflammation such as apical periodontitis.

Substance P Expression Is Elevated in Inflamed Human Periradicular Tissue

Substance P is a neuropeptide believed to be a major mediator of neurogenic inflammation. The aim of our study was to evaluate whether substance P levels are elevated in the clinical biopsies collected from inflamed periradicular or control tissue. In this study, the presence of substance P was examined in infected human periradicular granulation tissue and control tissue. Sections from 19 periradicular granulomas and pulp tissues from two healthy control teeth were examined using the immunohistochemical method. Substance P-expressing neutrophils, macrophages, and plasma cells were found in both acute and chronic periradicular granulomas. In addition, we observed the presence of neutrophils expressing substance P without concurrent clinical symptoms of acute inflammation. Our results are consistent with the hypothesis that substance P may be released from neutrophils in the inflamed region, and thus, substance P may modulate clinical inflammatory response by release from either neuronal or immunocompetent cell populations.

Gamma interferon (IFN-gamma) and IFN-gamma-inducing cytokines interleukin-12 (IL-12) and IL-18 do not augment infection-stimulated bone resorption in vivo

Periapical granulomas are induced by bacterial infection of the dental pulp and result in destruction of the surrounding alveolar bone. In previous studies we have reported that the bone resorption in this model is primarily mediated by macrophage-expressed interleukin-1 (IL-1). The expression and activity of IL-1 is in turn modulated by a network of Th1 and Th2 regulatory cytokines. In the present study, the functional roles of the Th1 cytokine gamma interferon (IFN-gamma) and IFN-gamma-inducing cytokines IL-12 and IL-18 were determined in a murine model of periapical bone destruction. IL-12-/-, IL-18-/-, and IFN-gamma-/- mice were subjected to surgical pulp exposure and infection with a mixture of four endodontic pathogens, and bone destruction was determined by microcomputed tomography on day 21. The results indicated that all IL-12-/-, IL-18-/-, and IFN-gamma-/- mice had similar infection-stimulated bone resorption in vivo as wild-type control mice. Mice infused with recombinant IL-12 also had resorption similar to controls. IFN-gamma-/- mice exhibited significant elevations in IL-6, IL-10, IL-12, and tumor necrosis factor alpha in lesions compared to wild-type mice, but these modulations had no net effect on IL-1alpha levels. Recombinant IL-12, IL-18, and IFN-gamma individually failed to consistently modulate macrophage IL-1alpha production in vitro. We conclude that, at least individually, endogenous IL-12, IL-18, and IFN-gamma do not have a significant effect on the pathogenesis of infection-stimulated bone resorption in vivo, suggesting possible functional redundancy in proinflammatory pathways.

Expression of MHC Class II, CD70, CD80, CD86 and pro-inflammatory cytokines is differentially regulated in oral epithelial cells following bacterial challenge

Oral epithelium may play a regulatory role in local immune responses when interacting with bacteria. The present study was undertaken to investigate the effects of selected bacterial pathogens found in periodontal and endodontic infections on oral epithelial cells. Expression of cell surface molecules (major histocompatibility complex (MHC) Class II, CD54, CD70, CD80 and CD86) and secretion of inflammatory cytokines (interleukin (IL)-1beta, IL-6, and tumor necrosis factor (TNF)-alpha) in response to selected bacterial challenge were examined on an immortalized oral epithelial cell line, HOK-18A and a skin epithelial cell line, HaCaT. Actinomyces viscosus, Actinomyces israelii, Fusobacterium nucleatum lipopolysaccharide (LPS) or primary human periradicular exudate from a granuloma were co-cultured with epithelial cells for 4 or 24 h. Subsequently, cell surface expression of MHC Class II, CD54, CD70, CD80 and CD86, along with pro-inflammatory cytokine levels were determined using flow cytometry, ELISA and RT-PCR. Results indicated that the selected oral bacteria have greater effects on oral versus skin epithelial cells. F. nucleatum increased MHC Class II and CD54 (ICAM-1) cell surface expression on HOK-18A and HaCaT cells. A. israelii also had enhancing effects on the expression of CD54 and MHC Class II. A. israelii and LPS induced a 2.8-fold (P < 0.001) and 4.4-fold (P < 0.005) TNF-alpha secretion, respectively, while F. nucleatum and LPS induced a 10-fold (P < 0.0004) and 6-fold (P < 0.01) IL-1beta secretion, respectively by HOK-18A. Interestingly, CD70, CD80, and CD86 were generally decreased upon bacteria and LPS challenge on HOK-18A. The effects of increased MHC Class II and decreased CD70 were also evident with challenge of human periradicular exudate on HOK-18A. The implications of the study are unique in that oral epithelial cells may play both activating and inhibitory roles in the host immune response towards infection by oral bacteria. We introduce a concept of 'dormancy' where the differential expression of key cell surface antigens on oral epithelial cells may keep the recruited immune effector cells in a state of unresponsiveness, thus contributing to the long term quiescent period observed in many periodontal and endodontic lesions.

Involvement of substance P, mast cells, TNF-alpha and ICAM-1 in the infiltration of inflammatory cells in human periapical granulomas

BACKGROUND

Substance P (SP), a potent proinflammatory peptide present in sensory neurons, is believed to be a major mediator of neurogenic inflammation. The aim of this study was to examine the localization and involvement of SP, mast cells and tumor necrosis factor-alpha (TNF-alpha)-positive cells in human periapical granulomas.

METHODS

Sections from seven periapical granulomas were stained using a variety of immunohistochemical methods.

RESULTS

SP-immunoreactive nerve fibers, mast cells and TNF-alpha-positive cells were found localized in the vicinity of blood vessels in all the samples of periapical granulomas. The vascular endothelial cells stained positively for E-selectin and intercellular adhesion molecule-1. SP, TNF-alpha-positive cells and E-selectin could not be detected in clinically healthy periodontal ligament, and served as a negative control.

CONCLUSION

Our findings suggest that SP, mast cells, TNF-alpha-positive cells and E-selectin may modulate the pathogenesis of apical periodontitis and may be responsible for stimulating the formation of granuloma with the resorption of periapical bone.

Immunohistochemical analysis of CD1a-labeled Langerhans cells in human dental periapical inflammatory lesions--correlation with inflammatory cells and epithelial cells

OBJECTIVE

Distribution and density of CD1a-labeled Langerhans cells (LCs) were examined in human dental periapical inflammatory lesions, and compared with inflammatory cell infiltration or epithelial cell proliferation.

MATERIALS AND METHODS

Eighty three periapical lesions (26 apical granulomas (AGs), 8 epitheliated granulomas (EGs), 34 radicular cysts (RCs), 15 residual radicular cysts (RRCs)) were collected. As control, specimens of periodontal ligaments including Malassez epithelial rests were curetted from 21 teeth. LC densities were measured and various degrees of inflammatory cell infiltration were examined immunohistochemically. Labeling indices for the cellular proliferation markers Ki-67 antigen and DNA topoisomerase II alpha were calculated in the epithelial components.

RESULTS

LCs were found in all periapical lesions but not in Malassez epithelial rests. LCs were more abundant in epithelial components than in subepithelial layers. Intraepithelial LCs were more frequent in RCs than in RRCs, whereas subepithelial LCs were less frequent in RRCs than in AGs and EGs. T lymphocytes consistently outnumbered macrophages, plasma cells and B lymphocytes. The range of the CD4/CD8-positive cell ratio differed according to the lesions. Increased LC density was associated with the severity of CD3-positive cell infiltration. Ki-67- and Topo II-LI showed various degrees of epithelial immunoreactivity. There was a significant correlation between LC density and proliferative potential of the epithelium in periapical lesions.

CONCLUSION

These findings suggested that LCs appeared to be associated with T lymphocyte infiltration and proliferative potential of the epithelial tissue in periapical lesions.

The presence of chemokine receptor (CCR5, CXCR3, CCR3)-positive cells and chemokine (MCP1, MIP-1alpha, MIP-1beta, IP-10)-positive cells in human periapical granulomas

The infiltration of leukocytes into inflammation sites such as observed in human periapical granulomas is considered to be mediated by chemotactic factors. In this study, we examined the presence of chemokine- and chemokine receptor-positive cells in samples obtained from human subjects by means of immunohistochemical methods. Macrophage chemotactic protein-1 (MCP-1), macrophage inflammatory protein (MIP)-1alpha, MIP-1beta and IFN-inducible protein 10 (IP-10)-producing cells were present in periapical granulomas. In addition, chemokine receptor CCR3-, CCR5-, and CXCR3-positive cells were also present. In contrast, no factor expression was observed in clinically healthy periodontal ligament, serving as a negative control. Our findings suggest that these chemokines are responsible for modulating the process of disease, such as human apical periodontitis.

Study of the expression of CD68+ macrophages and CD8+ T cells in human granulomas and periapical cysts

In the periapex, the interaction among inflammatory cells and microorganisms and their products results both in specific and nonspecific immune responses. Many studies have reported quantitative analysis of the immunocompetent cells in periapical lesions, but the exact ratio of these cells in cysts and granulomas remains unknown. In the present study, we undertook a quantitative analysis of CD68+ cells and CD8+ T cells in human periapical granulomas and cysts. Immunoperoxidase staining revealed that CD68+ cells were present in both lesions, with no statistically significant difference, mainly distributed in the inner portion of the lesion, where the inflammation site is more active. On the other hand, CD8+ lymphocytes were more numerous in cysts. Thus, it appears that CD8+ T cells may play a more important role in a later phase of periapical lesion progression, probably exerting regulatory or cytotoxic functions in cellular immune response, which may lead to the stabilization of these lesions.

Presence of IFN-gamma and IL-4 in human periapical granulation tissues and regeneration tissues

To study mediators associated with the progression of disease and the process of bone regeneration in human apical periodontitis, we examined samples of periapical granulation tissues and regeneration tissues obtained from five patients by use of immunohistochemical methods. Periapical granulation tissues were found to contain a large number of CD4-positive T cells and CD68-positive monocytes/macrophages (CD4: 35.2%, CD68: 32.7%). The CD4-positive T cells and CD68-positive monocytes/macrophages were predominantly present in regeneration tissues (CD4: 62.1%, CD68: 16.0%). In these the percentages of CD4-positive T cells were higher as compared with periapical granulation tissues (from 35.2% to 62.1%). In periapical granulation tissues, CD4-positive T cells stained positively for interferon-gamma (IFN-gamma) and negatively for interleukin-4 (IL-4). In regeneration tissues, IL-4-producing cells could be detected. However, IFN-gamma-producing cells could not be detected. These results suggest that IFN-gamma and IL-4 may modulate the pathogenesis of infectious disease and the process of bone regeneration in local inflammation sites such as human apical periodontitis.

Evaluation of immunoglobulin G synthesizing plasma cells in periapical granuloma and cyst

Immunoglobulin synthesizing plasma cells for IgG were quantitated in 20 periapical granulomas and 20 periapical cysts, using unlabelled antibody peroxidase-antiperoxidase complex method. Result showed that immunoglobulin G producing plasma cells were predominant in periapical cyst as compared with periapical granuloma. A statistical significant relation was observed between these two lesions.

Tumor necrosis factor-alpha and transforming growth factor-beta1 in chronic periapical lesions

OBJECTIVE

Proinflammatory cytokines are involved in the pathogenesis of periapical lesions. The purpose of this study was to evaluate the presence of the cytokines tumor necrosis factor-alpha (TNF-alpha) and transforming growth factor-beta(1) (TGF-beta(1)) in periapical pathosis and to determine their relationship to the size of the lesions.

STUDY DESIGN

One tooth from each of 25 patients was root-end resected, and the periapical lesion was collected. The amounts of TNF-alpha and TGF-beta(1) were assessed by enzyme-linked immunosorbent assay.

RESULTS

TGF-beta(1) was detected in 21 of 25 lesions. In samples with scar tissue, no TGF-beta(1) activity was detected. A statistically significant correlation was found between TGF-beta(1) per milligram of tissue and the diameter of the lesions. TNF-alpha was detected in only 2 samples.

CONCLUSIONS

TGF-beta(1) was present in periapical granulomas and cysts but not in lesions with scar tissue. The correlation between the amount of TGF-beta(1) per milligram of tissue and the size of the lesion was significant.

Protective and destructive immune reactions in apical periodontitis

Apical periodontitis is initiated primarily by the mixed microflora of infected root canals. Continuous flow of bacteria and their products through the apical foramen induces influx, activation and coordinated interaction of immune-inflammatory cells within the periapical area. Successful mobilization of host defense mechanisms prevents abundant extraradicular bacterial invasion. However, anti-infective effector mechanisms are not restricted to killing the invading microorganisms but also destroy normal tissue components and induce bone absorption, resulting ultimately in the loss of the affected teeth. Moreover, autocrine and paracrine loops of stimulation may lead to the perpetuation of the local inflammatory lesion and may also alter the function of remote tissues and organs. This review attempts to summarize current knowledge about the pathogenic mechanism of apical periodontitis, focusing on the formation of a special granulation tissue that effectively fights bacteria originated from the infected pulp chamber and, by exerting this protective function, also contributes to harmful local and distant events. The dynamic equilibrium between defensive and destructive mechanisms may provide a pathobiological basis for better understanding of clinical signs and symptoms of various forms of apical periodontitis lesions and influence treatment strategy and practice.

Cytokine expression in periapical granulation tissue as assessed by immunohistochemistry

The aims of this study were to investigate the expression of pro-inflammatory, anti-inflammatory and immune-related cytokines present in periapical lesions. We investigated the expression of cytokines: namely interleukins IL-2, IL-4, IL-6, IL-10 and interferon-gamma (IFN-gamma) in formalin-fixed, paraffin-embedded sections of periapical granulation tissue. The study samples were biopsies from 24 patients with periapical lesions: 12 with periapical granulomas and 12 patients with radicular cysts. Immunohistochemistry was also performed on tonsillar tissue which served as a control. We utilised a set of specific monoclonal antibodies and polyclonal monospecific antibodies to detect cells that expressed the different cytokines within the tissues. We also considered the nature of the periapical immune response by investigation of the T-helper 1 (Th-1) and T-helper 2 (Th-2) lymphocyte subsets using their cytokine profile, i.e., Th-1: IL-2 and IFN-gamma and Th-2: IL-4, IL-5 and IL-6. Only a few cells were weakly positive for the IL-2 protein in each of the tissue sections. Cells that expressed IL-4 or IL-6 were far more numerous than cells that expressed either IL-2 or IFN-gamma. Thus, we demonstrated a greater number of Th-2 cells in periapical lesions. This relative ratio of the T-cell subsets underlines the importance of the anti-inflammatory mechanisms taking place in the diseased tissue manifested by the wide array of IL-10-expressing cells: B cells, T suppressor cells (CD8 (+)) and tissue macrophages. The numbers of inflammatory cells expressing the anti-inflammatory molecules far outnumbered the cells that expressed pro-inflammatory cytokines. Thus, the downregulation of the inflammatory response and the predominant Th-2 or humoral immune response in periapical periodontitis may be important features that dictate the outcome of the disease process in the periapical lesion.

CD45/isotypes expression in the immune cells of human periapical lesions

Expression of some leukocyte antigens (including CD45) and its isoforms (CD2, CD4, CD5, CD6, CD7, and CD8) was examined in the human periapical granulation tissue samples in the present study. The majority of the infiltrating cells expressed heavy molecular-weight isoforms of the CD45 antigen. Expression of CD2, CD5, CD6, and CD7 antigens was also detected, implying significant roles for these antigens in the immune reaction taking place in periapical lesions. This suggests that the immune response taking place at the periapical region is predominantly cellular and the humoral responses to antigenic challenge are conducted mainly by regional lymph nodes.

Differential in situ distribution of interleukin-8, monocyte chemoattractant protein-1 and Rantes in human chronic periapical granuloma

In situ distribution of three prototype chemokines interleukin (IL)-8, monocyte chemoattractant protein (MCP)-1 and Rantes was determined in chronic human periapical granulomas by immunohistochemistry using monoclonal antibodies. IL-8 was found primarily in the cytoplasm of the Malassez epithelial cells. MCP-1 immunoreactivity was confined to the endothelial cells that lined small venules. Each of the three investigated chemokines, including Rantes, exhibited a characteristic binding pattern to the extracellular matrix of the lesion. The observed chemokines may play a role in establishing the cellular composition of chronic apical periodontitis, thus augmenting the intensity of local inflammation and tissue damage.

Macrophages in periapical lesions

Macrophages are major constituents of periapical granulomas. They have a central protective role in both innate immunity and adoptive, antigen-specific immune response. Macrophage activation may occur in periapical granulomas by cytokines produced by antigen-activated T-lymphocytes; by bacterial endotoxin, as part of the innate immunity; or by both these processes. Recent studies in athymic animals have shown that periapical granulomas may develop independently of T-lymphocytes. This observation reveals the major role that the activated macrophage may have in the formation of periapical lesions. Only a few of the macrophages in the periapical granuloma are activated. Current studies indicate that these activated cells are the source of the bone-resorbing cytokines in the periapical granuloma. Understanding the central role of the activated macrophage in the formation as well as the perpetuation of periapical lesions may lead to the development of new diagnostic and therapeutic tools in endodontics.

[Analysis of activated cells in apical granuloma]

The ratio and in situ distribution of CD3+ T-lymphocytes, CD4+ and CD8+ subsets, CD14+ macrophages, CD56+ natural killer cells and CD25+ activated T-lymphocytes and CD68+ activated macrophages were determined in 20 chronic peripical granulomas by immunohistochemical method using monoclonal antibodies. CD3+ T-lymphocytes made up about 50% of the mononuclear cells. CD14+ macrophages were distributed all over the area but their proportion was much less that that of the T-lymphocytes. CD56+ natural killer cells made up a small proportion of the cells. The major proportion of the T-lymphocytes and macrophages were in activated stage within the lesion.

Cell synthesis, proliferation and apoptosis in human dental periapical lesions analysed by in situ hybridisation and immunohistochemistry

OBJECTIVE

The role of structural and host defensive cells in periapical lesions has been assessed previously by morphometric and immunohistochemical studies. The aim of this study was to investigate the function of peri- apical cells by employing molecular techniques to estimate the cell synthetic activity, proliferation and apoptosis in these lesions. We specifically sought answers to the following questions. Which cells of the periapical lesions are quiescent or actively synthesising proteins? Do immune cells proliferate in this region in the same way as epithelial cells proliferate? Furthermore do cells in peri- apical lesions undergo apoptosis, and if so which cells exhibit this programmed cell death?

MATERIALS

Twenty-five periapical tissue samples (15 granulomas and 10 radicular cysts) were assessed. Poly-adenosine (poly (A)) RNA and ribosomal RNA (rRNA) bearing cells in formalin-fixed/paraffin-embedded peri- apical tissues were analysed by in situ hybridization (ISH) using digoxigenin-labelled oligo d (T) and 28S rRNA probes respectively in order to estimate cell synthetic activity. Furthermore, S-phase proliferating and cycling cells were examined by ISH using a histone probe and Ki-67 immunostaining so as to assess cellular proliferation. Mononuclear cells were further differentiated by immunohistochemistry (IHC) as T cells, B cells and macrophages. Apoptotic cells were determined by in situ end-labelling methodology for detecting fragmented DNA.

RESULTS

Poly (A) RNA (mostly messenger RNA) and 28S rRNA-expressing cells were detected in all samples. Plasma cells exhibited strongest staining for the two probes, with slight to moderate staining found in the epithelium, fibroblasts, macrophages, endothelial cells and lymphocytes, whereas almost all polymorphonuclear leucocytes (PMN) were negative for these probes. A few histone mRNA-expressing cells were detected in basal and suprabasal epithelial cells and mononuclear cells in 15/25 cases but their reactivity was weak. Ki-67 positive cells were found in all samples and their numbers were generally higher than histone mRNA positive cells. Apo- ptotic cells were detected in 23/25 cases and the majority of apoptotic cells were PMN which were engulfed by large cytophagocytic macrophages.

CONCLUSION

This study indicates that in dental periapical lesions, apoptosis occurs predominantly in PMN. It is evident that most cells apart from PMN are exhibiting synthetic activity but only epithelial cells undergo proliferation which implies that immune cells must proliferate at distant lymph nodes and travel to the periapical lesion rather than proliferating within the lesion. These results suggest considerable advantages in estimating gene expression within cells in addition to the immunohistochemical detection of cells to determine cell activity at inflamed sites. Clearly, functional cell synthetic activity, resolution and clearance systems operate in peri- apical cystic and granuloma lesions.

Eosinophil-derived transforming growth factors (TGF-alpha and TGF-beta 1) in human periradicular lesions

Inflammatory mediators of periradicular lesions are poorly understood. Transforming growth factors-alpha and -beta 1 (TGF-alpha and TGF-beta 1) have been linked with the cellular processes for both soft and hard tissue wound healing. The purpose of this study is to demonstrate the cellular sources of TGF-alpha and TGF-beta 1 mRNA and protein in periapical lesions by in situ hybridization and immunohistochemistry. Nine periapical granulomas and nine periapical cysts were examined. TGF-alpha mRNA and protein were not detectable in the granulomas examined. However, eosinophils surrounding the periapical cysts demonstrated both TGF-alpha mRNA and protein. The vast majority of eosinophils present in the periapical granulomas and cysts also demonstrated TGF-beta 1 mRNA and protein. Other cells producing TGF-beta 1 were lymphocytes, fibroblasts, and monocytes. The presence of wound repair cytokines, such as TGF-alpha and TGF-beta 1, suggests a mechanism by which the host inflammatory response may participate in the repair and remodeling of periapical tissues.

Cytotoxic T lymphocytes versus streptococcal colonization in periapical granulomas

Seventeen dental periapical lesions were investigated to study bacterial colonization. Periapical lesions, obtained after apicotomy, were also enzymatically desegregated to quantitatively analyze lymphocyte subpopulations by flow cytometry. Fourteen samples yielded a positive bacterial growth when homogenized and cultured. We isolated enough lymphocytes to make flow cytometric analysis from 12 samples. A significant increase in interleukin-2 receptor and ICAM-1 molecule expression on T cells was found, compared with peripheral blood lymphocytes. Furthermore, a decreased expression of interleukin-2 receptors and HLA DR molecules on CD8+ T cells was found in granulomas predominantly colonized by Streptococcus spp., compared with lesions predominantly colonized by strict anaerobes.

Distribution of interleukin-2 receptor alpha-chain and cells expressing major histocompatibility complex class II antigen in chronic human periapical lesions

In situ distribution of CD2+ T-lymphocytes, CD4+ and CD8+ T-cell subsets, CD14+ macrophages, interleukin-2 receptor alpha-chain (IL-2R alpha) and class II major histocompatibility complex antigen (major histocompatibility complex class II, HLA-DR) expressing cells were determined in 14 chronic human periapical granulomas by immunohistochemical method using monoclonal antibodies. CD2+ lymphocytes were rather evenly distributed within the classical granulation tissue and comprised 55% of the mononuclear cells. Macrophages were distributed all over the periapical area, but their proportion was much less than that of T lymphocytes. Both small, lymphocyte-like mononuclear cells and larger mononuclear cells resembling macrophages displayed mild to strong circumferential staining with the anti-HLA-DR antibody. The majority of lymphocytes expressed IL-2R alpha indicating the activated state of T cells within the lesion.

Interferon-gamma-producing cells and inducible nitric oxide synthase-producing cells in periapical granulomas

Periapical granulomas contain a large number of T lymphocytes and monocytes/macrophages and a small number of B lymphocytes and polymorphonuclear leukocytes. Sections from eight periapical granulomas were stained by a variety of immunohistochemical methods. The vascular endothelial cells stained positively for intercellular adhesion molecule-1 and vascular cell adhesion molecule-1. Helper T cells were identified by immunostaining for CD4 and stained positively for interferon-gamma (IFN-gamma). However, CD4-positive T cells did not stain for interleukin-4 (IL-4). Monocytes/macrophages were identified by immunostaining for CD68 and stained positively for IL-1alpha or inducible nitric oxide synthase (iNOS). IL-1beta could not be detected in the same samples. No cytokine expression was observed in B cells identified by immunostaining for CD20. IFN-gamma- and iNOS-positive cells could not be detected in clinically healthy periodontal ligament being used as a negative control. These results suggest that the IFN-gamma-producing T cells and iNOS-positive cells may modulate the progress of disease in local inflammation sites such as in periapical granulomas.

Detection of IgA subclasses and J chain mRNA bearing plasma cells in human dental periapical lesions by in situ hybridization

Humoral immune responses are implicated in the pathogenesis of human dental periapical lesions. To elucidate whether IgA-associated immune systems play a role in the lesions, the in situ hybridization technique was used to detect J chain mRNA expression, which is correlated with the secretion of dimeric IgA. In addition, IgA subclass mRNA-expressing cells were also investigated by double target in situ hybridization (ISH) methodology using digoxigenin- and biotin-labeled IgA subclass specific oligonucleotide probes. This double target ISH technique involved immunochemical detection with an alkaline phosphatase-conjugated antibody and a peroxidase conjugated avidin-biotin complex system to detect IgA subclass mRNA in the formalin-fixed, paraffin wax embedded periapical tissue sections. Twenty-four biopsy samples (16 periapical granulomas and 8 radicular cysts) were examined. IgA subclass mRNA positive plasma cells were detected in all samples. IgA1 mRNA-expressing cells were predominant both in granulomas and cysts (mean = 75.3 +/- 11.2%, 64.8 +/- 21.3%, respectively), and the IgA1 proportion was higher in granulomas than in cysts, although no significant difference was seen between the two lesions (p = 0.132). J chain mRNA positive cells were very sparsely detected in 21/24 cases. The median percentages of J chain mRNA positive cells/IgA mRNA positive plasma cells (4.7%, range 0.3-13.6%) in cysts were significantly higher than in granulomas (1.3%, range 0-7.7%; p = 0.03). This result supports the hypothesis that dimeric IgA may be more actively produced in radicular cysts than in granulomas. These features are thought to reflect the local activation of the periapical immune system in response to environmental factors and indicate that secretory IgA mediated immune defense systems appear to play little role in these lesions. Our results indicate that the IgA-associated immune response in periapical lesions is more similar to serum or systemic IgA responses than to mucosa-associated immune responses where dimeric IgA predominates.

Bone-resorptive cytokine gene expression in periapical lesions in the rat

Periapical bone destruction is an important pathogenic sequela of pulpal infection. Recent findings from this laboratory have demonstrated that most bone-resorbing activity in extracts of rat periapical lesions can be neutralized by an anti-interleukin (IL)-1 alpha antiserum. To further clarify pathogenic mechanisms, bone-resorptive cytokine messenger RNA (mRNA) expression was analyzed in developing rat periapical lesions. The molar teeth of 20 Sprague-Dawley rats were surgically exposed and left open to permit infection from the oral environment. Total cell RNA was isolated from periapical granuloma tissue obtained on days 3, 7, 15 and 30 after exposure. mRNA for IL-1 alpha, IL-1 beta and tumor necrosis factor alpha (TNF-alpha) was amplified by reverse transcription polymerase chain reaction, and levels were approximated by comparison to the parallel amplification of the housekeeping gene glyceraldehyde phosphate dehydrogenase. IL-1 alpha and TNF-alpha mRNA were both highly expressed beginning on day 7, increased on day 15, and declined somewhat on day 30. In contrast, IL-1 beta mRNA was expressed at much lower levels, but with similar kinetics. The kinetics of steady state IL-1 alpha and TNF-alpha mRNA levels were confirmed using the quantitative RNase protection assay, whereas IL-1 beta mRNA could not be detected by this technique. IL-1 alpha mRNA-expressing cells were identified using in situ hybridization and included infiltrating macrophages, as well as resident fibroblasts, endothelial cells and osteoclasts. These results demonstrate that the IL-1 alpha and TNF-alpha genes are highly expressed in developing periapical lesions in the rat and confirm previous studies at the protein level in this model.

Histochemical and immunocytochemical localization of dipeptidyl peptidases II and IV in human gingiva

Dipeptidyl peptidase (DPP) II and IV activities were demonstrated in unfixed cryostat sections of gingival tissue from chronic periodontitis patients using histochemistry with 2-methoxy-4-naphthylamine (MNA) substrates. In the case of DPP IV, enzyme localization was confirmed by immunocytochemistry with mouse monoclonal antihuman DPP IV (CD26) antibody. Inflammatory cells containing enzyme were identified in adjacent sections with mouse monoclonal antibodies directed against leukocyte differentiation antigens. Lys-Ala-MNA and Ala-Pro-MNA staining in acid buffer for DPP II was only found in a few fibroblasts in superficial tissue. Staining with Gly-Pro-MNA and Ala-Pro-MNA in alkaline buffer for DPP IV was localized in some CD4 and CD8 positive T lymphocytes, CD68 positive macrophages, and fibroblasts and these cells also reacted with the enzyme antibody. DPP IV-containing macrophages and T lymphocytes were seen in the epithelium. In deeper granulomatous tissue Gram positive and negative bacteria stained with the histochemical substrates, but not the DPP IV antibody. Fibroblast DPP II and IV might participate in cellular interactions with collagen, while T lymphocyte DPP IV may be involved in cell signalling.

Analysis of immunoglobulin-synthesizing cells in human dental periapical lesions by in situ hybridization and immunohistochemistry

Immunoglobulin (Ig) kappa (kappa) and lambda (lambda) light chain mRNA-expressing cells were investigated by in situ hybridization (ISH) to assess the local humoral immune response in human dental periapical lesions. Twenty-seven biopsy samples (17 periapical granulomas and 10 radicular cysts) were examined. Both types of light chain mRNA-positive cells were detected in formalin-fixed/paraffin-embedded tissue sections in all samples. Plasma cells showed weak to strong cytoplasmic staining with both probes and background staining was negligible. The ISH methodology is specific and sensitive in detecting Ig light chain mRNAs and retains cell morphology well. kappa to lambda ratios showed moderate variability for both granulomas and cysts (mean = 1.66 +/- 0.85 SD, 1.47 +/- 0.51, respectively). There was no significant difference in light chain distribution between granulomas and cysts. Ig kappa and lambda light chain proteins were also studied by immunohistochemistry (IHC) but the results were disappointing due to excessive background staining. This study confirms that Ig is locally produced in periapical lesions and that the ISH method localises Ig light chain-containing cells better than IHC. The wide variability in kappa/lambda ratio may support the concept of non-specific multibacterial infection in these lesions.

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

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

Detection of epidermal growth factor receptor in inflammatory periapical lesions

Epithelial cell proliferation is often observed in periapical lesions of endodontic origin. The mechanisms which stimulate the epithelial cell rests of Malassez to proliferate are not understood fully. Fifteen inflammatory periapical lesions (10 granulomas and five cysts) obtained from periapical surgery and six additional periapical lesions (four granulomas and two cysts) collected from extracted teeth were examined using immunohistochemical staining and 125I-EGF (epidermal growth factor) binding assay to detect the presence of epidermal growth factor receptor. The results indicated that the periapical lesions without epithelial cell proliferation had a weak immunoperoxidase staining or low specific binding of 125I-EGF. In contrast, the periapical lesions with epithelial cell proliferation and cyst formation exhibited a strong immunoperoxidase staining in the epithelial cells or high specific binding of 125I-EGF.

Histological findings of human leprosy periapical granulomas

Histological analysis of human leprosy periapical granulomas was conducted to study the histological responses to Mycobacterium leprae. Many Langhans-type giant cells and epithelioid cell tubercles were observed, although M. leprae were not detected in leprosy periapical granulomas. Although numerous T- and B-cells were infiltrated in leprosy periapical granuloma, the T-/B-cell ratio of leprosy is not changed to that of periapical granulomas isolated from normal patients. These findings suggested that human leprosy periapical granulomas develop as a result of immunological responses to M. leprae.

Mediators of acute and chronic periradicular lesions

Multiple mechanisms are involved in the pathologic changes associated with formation of acute and chronic periradicular lesions. Mechanical injury to the periradicular tissues can cause activation of several pathways of inflammation and release of nonspecific mediators. Continuous irritation of periradicular tissues can cause activation of several pathways of inflammation and release of nonspecific mediators. Continuous egress of antigens from a pathologically involved root canal can also result in one or a combination of the various types of immunologic reactions. A number of these reactions participate in the destruction of periradicular tissues. Because of complex interactions between the various components of these systems, the dominance of any one pathway or substance may be difficult to establish.

Interleukin-1 alpha and interleukin-1 beta periapical exudates of infected root canals: correlations with the clinical findings of the involved teeth

This study quantified the concentrations of interleukin-1 alpha (IL-1 alpha) and interleukin-1 beta (IL-1 beta) in the periapical exudates obtained from 69 single-rooted teeth using enzyme-linked immunosorbent assays, and examined their correlation with clinical findings of the involved teeth. Changes in the levels of these factors during root canal treatment were also investigated. The average levels of IL-1 beta (6.57 ng/ml) in periapical exudates were twice that of IL-1 alpha (3.25 ng/ml). The exudates containing pus showed significantly higher IL-1 alpha levels than those from the canals without pus (p < 0.01). The exudates from the canals with small radiolucent areas contained significantly higher IL-1 alpha levels than those from the canals with large radiolucent areas (p < 0.05). The tendency for there to be an increase in the levels of IL-1 alpha and a decrease in the levels of IL-1 beta was observed following root canal treatment. These observations suggest that IL-1 alpha and IL-1 beta are involved in the immunopathogenesis of periapical lesions and that IL-1 alpha and IL-1 beta may play different roles in the healing process of periapical lesions during root canal treatment.

The granulomatous response and oral cavity

The granulomatous response is a phylogenetically primitive specialized immunological reaction of the body to wall off an irritant, ingest and remove it, characterised by a localized collection of epithelioid cells, macrophages and lymphocytes. The cells forming the granuloma, its mechanism of formation and types of granuloma have been discussed. A classification of granulomatous diseases of the oral cavity based on etiology has been suggested.

Quantitation of circulating immune complexes in patients with chronic periapical lesions

Quantitation of circulating immune complexes (CIC) was done in 45 patients with chronic periapical lesions. The levels were compared with those of age-matched healthy individuals. Both patients with chronic periapical granuloma and periapical cysts showed significantly higher levels of CIC than the controls. This observation indicates that the continuous presence of root canal antigens may cause elevated levels of circulating immune complexes. The possibility of chronic periapical lesions acting as foci of infection is discussed, and the importance of early treatment of these conditions is emphasized.

Characterization of bone-resorbing activity in human periapical lesions

Extracts of human periapical granulomas were tested for the presence of bone-resorbing activity. All granulomas (10 of 10) contained low but significant levels of bone-resorbing activity, ranging from 2.1 to 4.9% treatment-% control/mg specific 45Ca release, as determined by the fetal rat long bone assay. Healthy periodontal ligament and dental pulp had no significant resorbing activity. In characterization studies, the resorbing activity in an extract pool was unaffected by the presence of polymyxin B, indicating an active moiety distinct from lipopolysaccharide. Resorbing activity was also unaffected by heating to 56 degrees C for 30 min, but was completely abolished by proteinase K treatment or heating to 70 degrees C, indicating that activity was largely protein mediated. Fast performance liquid chromatography gel filtration studies demonstrated that activity could be resolved to two major peaks, of M(r) 30,000 to 60,000 (I), and 15,000 to 20,000 (II), with a minor peak present at < 1,000 (III). Peak III was identified as prostaglandin E2 by radioimmunoassay. In inhibition studies, virtually all of the resorbing activity present was inhibited by anti-interleukin 1 beta (69%) and anti-tumor necrosis factor beta (66%) antisera, whereas anti-interleukin 1 alpha and antitumor necrosis factor alpha had no effect. Treatment with the cyclooxygenase inhibitor indomethacin also reduced activity by 74%. Taken together, these data demonstrate that most bone-resorbing activity present in chronic human periapical lesions is attributable to the action of resorptive cytokines interleukin 1 beta and tumor necrosis factor beta, acting via both indomethacin-dependent and independent pathways.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of inflammatory cell infiltrate in dental periapical lesions

Sixty-three dental periapical lesions were investigated in order to study the involvement of inflammatory and immunologic reactions in the pathogenesis and maintenance of chronic apical periodontitis. Of 61 well-preserved specimens, 38 were classified as granulomatous, 3 as exudative periapical granulomas and 20 as periapical scars. The quantitative composition of T-lymphocyte subpopulation and macrophages, the proportion of IgE-producing cells compared with other immunoglobulin producing plasma cells, and the tissue distribution of IgE-producing plasma cells compared with that of mast cells were determined in the granulomatous types of granulomas using immunofluorescent, immunohistochemical and enzymehistochemical methods. The results indicated a decreased ratio of helper/inducer versus cytotoxic/suppressor T-lymphocytes, a remarkably high proportion of macrophages, a low frequency of IgE-producing plasma cells with different localization when compared with that of mast cells. These observations suggest that T-lymphocytes and macrophages may play an important role in the complex events of tissue destruction and repair taking place in the periapical region.

Immunochemical and biological characterization of outer membrane proteins of Porphyromonas endodontalis

Outer membrane proteins (OMP) of Porphyromonas endodontalis HG 370 (ATCC 35406) were prepared from the cell envelope fraction of the organisms. The cell envelope that had been obtained by sonication of the whole cells was extracted in 2% lithium dodecyl sulfate and then successively chromatographed with Sephacryl S-200 HR and DEAE-Sepharose Fast Flow. Two OMP fractions, OMP-I and OMP-II, were obtained, and their immunochemical properties and induction of specific antibodies were examined. The OMP-I preparation consisted of a major protein with an apparent molecular mass of 31 kDa and other moderate to minor proteins of 40.3, 51.4, 67, and 71.6 kDa, while the OMP-II preparation contained 14-, 15.5-, 27-, and 44-kDa proteins as revealed by sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis. OMP-I was found to form hydrophilic diffusion pores by incorporation into artificial liposomes composed of egg yolk phosphatidylcholine and dicetylphosphate, indicating that OMP-I exhibited significant porin activity. However, the liposomes containing heat-denatured OMP-I were scarcely active. Spontaneous and antigen-specific immunoglobulin M (IgM)-, IgG-, and IgA-secreting spot-forming cells (SFC) enzymatically dissociated into single-cell suspensions from chronically inflamed periapical tissues and were enumerated by enzyme-linked immunospot assay. In patients with radicular cysts or dental granulomas, the major isotype of spontaneous SFC was IgG. In radicular cysts, the OMP-II-specific IgG SFC represented 0.13% of the total IgG SFC, while the antigen-specific IgA or IgM SFC was not observed. It was also found that none of these mononuclear cells produced antibodies specific for OMP-I or lipopolysaccharide of P. endodontalis.

Quantitative analysis of immunocompetent cells in human periapical lesions: Correlations with clinical findings of the involved teeth

Human periapical lesions develop as a result of a pathological immune response to continuous stimuli from infected root canals. This study identified the immunocompetent cells in such lesions immunohistochemically and quantified them to examine their interrelationships and correlations with clinical findings. The number of IgG-containing cells in CD4+ cell (Th/i)-rich lesions (> or = 55 CD4+ cells/2 x 10(4) microns 2) was significantly larger than in CD4+ cell-poor lesions (< 55 CD4+ cells/2 x 10(4) microns 2). This indicated that the CD4+ cells and the IgG-containing cells acted together against antigenic stimuli. The proportion of T cells in the mononuclear infiltrates varied with the size of the periapical lesions. The proportion of CD11+ cells (monocytes/macrophages) was significantly larger in lesions which showed a positive reaction to percussion or were tender on palpation than in the lesions without these symptoms. These observations suggest that T cells may play an important role in the development of periapical lesions and that CD11+ cells may be involved in the development of symptoms.

Influence of surgical treatment of periapical lesions on serum and blood levels of inflammatory mediators

Changes in the serum levels of immunoglobulin IgA, IgG, IgM, positive acute phase proteins and complement activity, as well as the lymphocyte subpopulations and the neutrophil leucocyte-related chemiluminescence in the blood of patients with apical granuloma as related to endodontic and surgical treatment were investigated. Measurements were performed on admission, and 7 days and 3 months after the treatment. Elevated IgM concentration, positive acute-phase protein levels and spontaneous whole-blood chemiluminescence were noted at admission. However, a significant decrease in the serum level of each of the six investigated acute-phase proteins, and in the spontaneous chemiluminescence of blood was observed during the 3-month follow-up period. The significant increase in serum complement activity following therapy suggests that complement fixation might have occurred in these patients. A significant increase in the ratio of early sheep erythrocyte rosette-forming lymphocytes was also observed. The results of this study provide evidence for complete recovery after elimination of local inflammation by proper endodontic treatment and apicectomy in patients with apical granuloma.

Immunoreactivity for interleukin 1-beta and tumor necrosis factor-alpha and ultrastructural features of monocytes/macrophages in periapical granulomas

Interleukin 1 (IL-1) and tumor necrosis factor (TNF) have recently been shown to be involved in bone resorption, and because macrophages constitute a significant part of human periapical granulomas, it is reasonable to suspect that they may secrete IL-1 and TNF. The purpose of our investigation was to detect and characterize IL-1 beta- and TNF-alpha-producing cells in human periapical granulomas. Fresh tissue samples obtained during surgery from 10 patients with previously untreated teeth and histologically established periapical granulomas were studied with light and electron microscopy and with immunohistochemical analysis with monoclonal antibodies against IL-1 beta and TNF-alpha. There were very few IL-1 beta + and TNF-alpha + cells present in periapical granulomas, and the positive cells had monocyte/macrophage morphology. The IL-1 beta + cells were located mainly in areas of active exudation and were surrounded by and/or were in close contact with lymphoid cells, whereas TNF-alpha + cells were scattered and in contact with or near other inflammatory cells at the periphery of active granulation tissue. This suggests that the IL-1 beta + cells may act in a paracrine manner to activate lymphoid cells. The ultrastructural findings showed that only some macrophages are adapted to extracellular secretion rather than phagocytosis. These modified macrophages could be the major producers of interleukins in tissues. Occasionally, they have plasmacytic or plasmacytoid features resembling the so-called "plasmacytoid monocytes". Only a minor fraction of the monocytes/macrophages (representing about 40% of the inflammatory cells) is in an active cytokine-producing state.(ABSTRACT TRUNCATED AT 250 WORDS)

[Cellular immunity in human periapical granuloma]

Numerous authors have produced different types of immunoglobulins in analyses of the human periapical granuloma. The present study examines the cellular immunity of the human periapical granuloma, and in particular the distribution of the lymphocyte sub-populations and the macrophage population. The technique used was that of cell surface marking, using monoclonal antibodies on frozen sections. The results reveal equal proportions of inductor T lymphocytes and suppressor T lymphocytes (whereas healthy tissue shows a ratio of 2/1), which explains the chronic nature of the lesion as far as the immune reaction is concerned. The presence of numerous macrophage cells shows that there are important local immune reactions.