Cyclosporin A upregulates prostaglandin E2 production in human gingival fibroblasts challenged with tumor necrosis factor alpha in vitro

The effect of Cyclosporin A (CsA) on prostaglandin E₂ (PGE₂) production in human gingival fibroblasts challenged with tumor necrosis factor alpha (TNF-α) was studied. TNF-α (1-100 ng/ml) dose-dependently stimulated PGE₂; formation in 24 h cultures. CsA (1-100 ng/ml) did not induce PGE₂; formation itself but potentiated TNF-α induced PGE; formation in gingival fibroblasts in a manner dependent on the concentrations of both CsA and TNF-α. TNF-α (10 ng/ml) stimulated the release of [³H]-arachidonic acid (A.A) from prelabelled fibroblasts that was potentiated by CsA (100 ng/ml). Addition of exogenous unlabelled AA (5-20 μM/ml) to the cells resulted in enhanced PGE₂: formation that was not potentiated by CsA (100 ng/mi). Furthermore. CsA (100 ng/ml) did not further increase the level of cyclooxygenase-2 mRNA induced by TNF-α (10 ng/ml). although PGE₂ formation was enhanced. The results indicate that CsA and TNF-α act in concert on PGE₂ formation in gingival fibroblasts. which may be of importance in the pathogenesis of gingival overgrowth induced by the drug.     

An immunocytochemical study of the inflammatory cell infiltrate and epithelial expression of HLA-DR in odontogenic cysts

The presence and distribution of lymphocytes, Langerhans cells, HLA-DR' infiltrating cells and the expression of HLA-DR by lining epithelium was investigated in the walls of odonlogenic cysts using an indirect immunoperoxidase method on acetone-fixed cryostat sections. The 23 cysts studied consisted of 14 dental (radicular) cysts, 5 keratocysts, 2 dentigerous cysts, 1 surgical ciliated cyst and 1 incisive canal cyst. The cell populations detected in the walls of all cysts were similar and consisted of HLA-DR+ macrophage-type cells and a mixture of T and B lymphocytes. Analysis of the T cell subsets revealed that in all cases the CD4⁺, T_h/i subset predominated over the CD8⁺, T_s/c subset. 18/22 cyst linings contained cells expressing a Langerhans cell phenotype (CD1⁺). Cytoplasmic epithelial expression of HLA-DR was detected in 7/22 specimens. Neither the presence of HLA-DR⁺ epithelial cells nor LC were restricted to a given type of cyst. These findings indicate the occurrence of similar cellular processes irrespective of the proposed developmental or inflammatory aetiology of these lesions.     

Reduced number of Langerhans cells in oral mucosal washings from HIV-1 seropositives

In order to elucidate mucosal immunity in HIV-1 seropositive individuals, we investigated oral mucosa washings from 20 HIV-1 seropositive patients for the presence of Langerhans cells (LC) and HIV-1 antigen-positive cells, and compared the results with those obtained from 20 HIV-l seronegative healthy individuals. Monoclonal antibodies directed against CDla, HLA-DR, CD3, and p24 were used to identify LC, T cells and HIV-l core-antigens, respectively. In oral mucosa washings from HIV-l seropositive patients there was a significant reduction in the number of CDla⁺ cells as compared with the healthy subjects. HIV-1 antigen-positive cells were not detected. The reduction of LC in oral mucosa washings from HIV-l seropositive patients is probably associated with HIV-l infection. The frequent occurrence of oral mucosal disorders in HIV-l infected patients may in part be caused by a reduced LC-number and/or function.     

High numbers of T cells in gingiva from patients with human immunodeficiency virus (HIV) infection

A quantitative, immunohistologic evaluation of CD3⁺, CD4⁺and CD8⁺ cells was carried out on gingival biopsies from 25 HIV-infected persons with gingivitis or periodontitis and 13 HIV-seronegative persons with periodontitis. CD3⁺ T cells were found in all biopsies. CD8⁺ cells were significantly more numerous and the CD4⁺/CD8⁺ ratio was significantly decreased in the gingival connective tissue of the HIV⁺ patients (P < 0.05). The number of CD4⁺ lymphocytes subjacent to the pocket epithelium was moderately lower in the HIVH patients as compared to the HIV⁺ patients (P < 0.05). HIV⁺ patients with a history of necrotizing periodontal disease had fewer CD4⁺ cells subjacent to the oral gingival epithelium than patients without such disease (P < 0.05). The general HIV-related changes in T lymphocyte numbers were therefore reflected in inflamed gingival tissues. HIV⁺ patients had, however, significantly higher CD4⁺/CD8⁺ ratios in gingiva than in peripheral blood (P < 0.05), indicating that CD4⁺ T cells are actively recruited to gingiva, even in cases of extreme CD4⁺ T lymphocytopenia.     

Distribution of Langerhans cells in clinically healthy human gingival epithelium with special emphasis on junctional epithelium

Abstract – Twenty-one biopsies of clinically healthy marginal gingiva from children, who performed conventional oral hygiene but received no additional professional prophylaxis, were studied in order to obtain information on distribution and density of Langerhans cells (LC) in the oral gingival epithelium (OGE), the sulcular epithelium (SE) and the junctional epithelium (JE). A simple freeze-separation technique was found to create acceptable histomorphology of JE in specimens obtained adherent to teeth, while partially and non-adherent ones were rejected. The majority of LC in OGE, were highly dendritic and stained intensively with OKT6 monoclonal antibodies. The distribution was network-like with a density of 21.0± 3.2 LC/0.1 mm² crosssectional epithelial area. A similar although less dense distribution was found in SE (8.6 ± 3.0 LG/0.1 mm²). These observations, confirm previous findings. In JE 2 groups of LC were identified: 1) Weakly stained LC with very few and short dendrites distributed in a scattered way (2.8± 1.4 LC/0.1 mm²) in the apical three-fourths of JE in most specimens. Present evidence suggests that these cells might be immature cells of Langerhans lineage. 2) Clusters of LC (9.4 ± 2.9 LC/0.1 mm²) with dendrites of moderate lengths and numbers and a varied fluorescence intensity; they were found in a few specimens in the coronal one-fourth of JE and at the border zone to SE. Such clusters might represent genuine variation in the distribution of LC or reactions to initial/ early plaque formation.     

Effect of phenytoin on interleukin-1β production in human gingival fibroblasts challenged to tumor necrosis factor αin vitro

Effects and interaction of tumor necrosis factor α (TNFα) and the antiepileptic drug phenytoin (PHT) on interleukin-1β (IL-1β) production as well as on prostaglandin E₂ (PGE₂) formation were studied in gingival fibroblasts in vitro. TNFα, in contrast to PHT, dose-dependently stimulated the production of cell-associated IL-1β. The stimulatory effect of TNFα on IL-1β production was accompanied by enhanced PGE₂ formation. When PHT and TNFα were added simultaneously, the drug potentiated the stimulatory effect of TNFα on both IL-Iβ production and PGE₂ formation. The major PHT metabolite, p-HPPH, did not affect IL-1β production, either alone or in combination with TNFα. The production of IL-1β induced by TNFα and the combination of TNFα and PHT was further enhanced in the presence of the prostaglandin endoperoxide (PGH) synthase inhibitors, indomethacin and flurbiprofen. The PHT-mediated enhancement of TNFα-induced IL-1β production and PGE₂ formation in gingival fibroblasts may be an important link in the pathogenesis of gingival overgrowth induced by PHT.     

Distribution of macrophage lineage cells in rat gingival tissue after topical application of lipopolysaccharide: an immunohistochemical study using monoclonal antibodies: OX6, ED1 and ED2

To discuss the role of macrophage lineage cells on the periodontal tissue destruction, we immunohistochemically examined the phenotype and the dynamics of macrophage lineage cells 1 or 3 h or 1, 2, 3 or 7 d after topical application of LPS (5 mg/ml in physiological saline) from the rat gingival sulcus using 3 monoclonal antibodies: OX6 (antigen-presenting cells), ED1 (monocytes, macrophages and dendritic cells) and ED2 (resident macrophages). We could detect at least 3 different types of macrophage lineage cells, namely OX6⁺/ED1⁺/ED2⁻ dendritic cells and exudate macrophages and ED2⁺ resident macrophages. After LPS application the majority of macrophage lineage cells accumulated in the subjunctional epithelial area were newly extravasated OX6⁺/ED1⁺/ED2⁻ dendritic cells or macrophages. The number Department of Oral Pathology, Hiroshima of these cells increased progressively with time and reached a maximum level at University School of Dentistry, d 2. On the other hand, number and tissue distribution of ED2⁺ resident macrophages did not change. These results indicate that several types of macrophage lineage cells exist in rat gingival tissue and suggest that dendritic cells and exudate macrophages transiently accumulated after LPS application are responsible for various host immune response and tissue destruction caused by LPS.     

Immunocompetent cells in oral candidiasis of HIV-infected patients: an immunohistochemical and electron microscopical study

OBJECTIVE: The purpose of this study was to elucidate the pathogenesis of oral candidiasis, a common cause of discomfort and social impairment among HIV-infected individuals.
STUDY DESIGN, MATERIALS AND METHODS: The oral mucosal immune system cells were analysed by immunohistochemistry and electron microscopy in biopsies from five erythematous and four pseudomem-branous candidiasis cases and were compared with those from seven HIV-positive and 10 HIV-negative controls without candidiasis.
RESULTS: The superficial lamina propria and basal epithelial layer was populated by CD1a⁺ Langerhans cells with infiltration of CD8⁺ lymphocyteS. Within the submu-cosa are CD36⁺ dendritic macrophages and lymphocytes, although CD4⁺ subsets were absent from the infiltrate. The expression of human leukocyte antigen system, DR locus (HLA-DR) and leukocyte specific adhesion molecules was low in erythematous, yet more marked in pseudomembranous candidiasiS. In the pseudomembra-nous form, CD14⁺ leukocytes were found in the basal epithelial layer. Langerhans cells were significantly more numerous and were richer in dendrites and Birbeck granules in erythematous than in pseudomembranous can-didiasis.
CONCLUSIONS: Candidiasis is associated with alterations in the number and differentiation of lymphocytes and dendritic cells, being more severe in the pseudo-membranous than erythematous form. We propose that these alterations play a role in the pathogenesis and evolution of the disease.     

Mycoplasma salivarium in human gingival sulci

The prevalence and quantity of mycoplasmata in the gingival sulcus area of periodontally diseased and periodontally healthy subjects was tested. Mycoplasma salivarium was the predominant sulcular species and occurred in a significantly higher percentage of diseased subjects than healthy subjects (p<.0005) (86.7 % vs 31.8 %). When mycoplasmata were present in the sulcus their concentration was usually 10⁶–10⁷ per gram of fluid whereas the concentration in saliva was approximately 100 to 1000 fold less. Therefore M. salivarium appears to be primarily a sulcular organism. M. salivarium may be part of the complex plaque which appears to produce gingivitis.     

Expression and activity of thrombomodulin in human gingival epithelium: in vivo and in vitro studies

Epidermal keratinocytes thrombomodulin (TM) has been shown to regulate thrombin at sites of cutaneous injury in addition to a role for epidermal differentiation. TM, a major anticoagulant proteoglycan of the endothelial cell membrane, is a thrombin receptor that acts as a co‐factor for protein C activation. Thrombin has pro‐inflammatory effects for periodontitis. However, little is known about TM in gingival tissue with periodontitis. We used immunohistochemistry to examine expression of TM in gingival epithelium from patients with periodontitis. In vitro , we observed TM expression at varying Ca²⁺ concentrations by confocal laser scanning microscopy, examined the expression of TM mRNA and tested TM co‐factor activity. Furthermore, we measured TM concentration in gingival crevicular fluid (GCF) from 11 severe adult cases of periodontitis using enzyme‐linked immunosorbent assay. Immunoreactive TM was present in gingival epithelium and junctional epithelium, and was reduced in inflamed gingival epithelium compared to healthy gingival epithelium. Ultrastructurally, TM, including microvilli, was observed on the cell membrane. TM localization in cells cultured in 0.09 m m Ca²⁺ differed from that in cells exposed to 1.2 m m Ca²⁺. Northern analysis demonstrated TM mRNA in gingival keratinocytes more than in human umbilical vein endothelial cells (HUVEC). Gingival keratinocytes also facilitated protein C activation by thrombin, although less strongly than HUVEC. TM in GCF at sites with bleeding on probing in patients was significantly elevated ( p <0.001, Student's t ‐test). TM in gingival epithelium may regulate thrombin activity at sites of coagulation and inflammation with periodontal disease, although inflammation may impair this regulation of thrombin.     

Influence of phenytoin on cytoplasmic free Ca2+ level in human gingival fibroblasts

Abstract— Influence of 5,5-diphenylhydantoin (phenytoin;PHT) on the cytoplasmic free Ca²⁺ concentration, [Ca²⁺]ⁱ, was studied in fura 2 loaded adherent monolayers of human gingival fibroblasts derived from three patients before and after 9 months of PHT therapy. In the patient where gingival overgrowth developed during PHT medication (responder), addition of PHT to gingival fibroblasts derived before PHT medication induced a transient extracellular Ca²⁺ dependent increase in [Ca²⁺]ⁱ. In a non-responder patient, where gingival overgrowth did not develop during the same period of PHT therapy, addition of PHT to gingival fibroblasts derived before the start of medication did not significantly affect [Ca²⁺]_i. Under extracellular Ca²⁺ deficient conditions, addition of PHT to serum-starved fibroblasts derived from the two categories of patients before the medication resulted in an increase in [Ca²⁺]_i. In fibroblasts derived from the responder patient during PHT medication, in contrast to those from the non-responders (n = 2), the basal level of [Ca²⁺]_i was significantly decreased. The results indicate that, in the cases studied, there is a relationship between PHT induced alterations in [Ca²⁺]_i in gingival fibroblasts and the clinical development of gingival overgrowth.     

Oral mucosal lesions in experimental graft-versus-host disease: morphological and immunohistochemical characterization of infiltrating cells

To facilitate recognition of the oral mucosal lesion that develops in rats with graft-versus-host disease (GVHD) induced by injecting spleen cells of parental strain rats (Brown Norway) into non-irradiated (Brown Nonvay×Lewis) F1 hybrid rats, we followed the development of the tongue lesion histologically and immunohistochemically. This assessment revealed an increase in the number of MHC class II⁺ cells with dendritic shape in the lamina propria to be the earliest stage of the tongue lesions in GVHD rats. The subsequent mononuclear cell infiltration with epithelial cell destruction, characteristic of GVHD. consisted of CD8⁺ cells and macrophages. Our findings seem to indicate that MHC class II⁺ cells with dendritic shape may provide antigen presentation in the induction of local immunological responses, including tissue destruction, by CD8⁺ cells and macrophages in the tongue of GVHD rats.     

Lectin binding to chronic inflammatory gingival tissue: possible adhesion mechanisms based on lectin-carbohydrate interactions

In this study, we analyzed the expression of different leukocyte surface antigens, of the adhesion molecules ELAM-1 and GMP-140 and binding of various lectins and neoglycoproteins in inflamed gingival tissue. Cell suspensions from collagenase-digested gingiva were analyzed by flow cytometry in a FACScan. The expression of ELAM-1, GMP-140, carbohydrate structures and lectins in gingival specimens was also studied by immunohistochemistry. Gingival tissue of patients with active periodontal disease contained between 5% and 50% CD45⁺ mononuclear cells, consisting mainly of CD19⁺ cells (B lymphocytes). CD62, resembling GMP-140, and ELAM-1 were strongly expressed on endothelial cells of these patients. Control subjects usually contained almost no CD45⁺ cells in their gingiva and no CD62⁺ or ELAM-1-positive endothelial cells could be found in 5 of 6 control persons. Analysis of the glycosylation pattern revealed staining of infiltrating cells by peanut agglutinin (PNA; specificity for galactose), whereas soy bean agglutinin (SBA; specificity for N-acetyl-galactosamine) bound to epithelial cells. An endogenous lactosyl-specific lectin could be detected on endothelial cells by binding of lactosyl-BSA. Ulex europeus I agglutinin (UEA-1, specific for fucose) showed selective staining of endothelial and epithelial cells. Expression of a fucose-binding lectin, demonstrated by binding of fucosylated BSA, could be found on infiltrating cells. The adhesion molecules ELAM-1 and GMP-140 seem to be involved in cell adhesion during chronic inflammation of the gingiva. Interaction of other carbohydrate residues with endogenous lectins might resemble additional adhesion mechanisms inflamed gingiva.     

Toll-like receptors 2 and 5 in human gingival epithelial cells co-operate with T-cell cytokine interleukin-17

Background/aim:  Periodontitis begins as the result of perturbation of the gingival epithelial cells caused by subgingival bacteria interacting with the epithelial cells via pattern recognition receptors. Toll-like receptors (TLRs) have been shown to play an important role in the recognition of periodontal pathogens so we have studied the interaction of TLR ligands with TLR2 and TLR5 for cytokine production in the cultures of gingival epithelial cells.
Methods:  Immunohistochemistry was used for the localization of TLR2 and TLR5 in tissue specimens. Enzyme-linked immunosorbent assays were performed to detect the levels of interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α), released from gingival epithelial cell cultures following stimulation with TLR ligand alone or in combination with IL-17.
Results:  Both TLR2 and TLR5 were increased in periodontitis (2128 ± 159 vs. 449 ± 59 and 2456 ± 297 vs. 679 ± 103, respectively, P  < 0.001) including gingival epithelial cells that stained strongly. Cultured gingival epithelial cells stimulated with their respective ligands (HKLM, a TLR2 ligand that is also found in Porphyromonas gingivalis , and flagellin, a TLR5 ligand that is also found in Treponema denticola ) produced both IL-1β and TNF-α. To mimic T-cell help, IL-17 was added. This further greatly enhanced TLR ligand-induced IL-1β ( P  < 0.001) and TNF-α ( P  < 0.01) production.
Conclusions:  These findings show how pathogen-associated molecular patterns, shared by many different periodontopathogenic bacteria, stimulate the resident gingival epithelial cells to inflammatory responses in a TLR-dependent manner. This stimulation may be particularly strong in periodontitis and when T helper type 17 cells provide T-cell help in intercellular cooperation.     

Response of human gingival fibroblasts to prostaglandins

The effects of various prostaglandins (PGs) on the functions of human gingival fibroblasts (Gin-1 cells; ATCC CRL 1292) were examined by phase-contrast microscopy, cell-counting and radioautographic experiments. Tested PGs were PGA₁, PGA₂, PGB₁, PGB₂, PGD₂, PGE₁, PGE₂, PGF₁α, PGF₂α, PGI₂, 6-keto-PGF₁α, 9α-11α-methanoepoxy-PGF₂α, and thromboxane (TX) B₂. PGA₁, and PGD₂ at 30 μM caused morphological deformation of Gin-1 cells. All the PGs tested at 30 μM suppressed the proliferation of Gin-1 cells in the logarithmic growth phase. Furthermore, all the PGs tested at 10 μM suppressed DNA synthesis, collagen synthesis, and noncollagenous protein synthesis in confluent Gin-1 cells, while exerting no effect on GAG synthesis. The concentrations of PGs used are beyond those found in healthy gingiva. However, in periodontitis the local concentrations of some PGs within the gingiva are expected to be extremely elevated beyond the physiological level. These results suggest that PGs may play an important role as a negative regulator in metabolism and some pathologic gingival conditions by suppressing the functions of gingival fibroblasts.     

Interaction of Porphyromonas gingivalis with gingival epithelial cells maintained in culture.

Interactions between Porphyromonas gingivalis and gingival epithelial cells were investigated. Gingival epithelial cells were cultured from surgically removed gingival tissue. Electron microscopy demonstrated adherence of P. gingivalis to the cell membranes and microvilli followed by internalization of the bacteria into the epithelial cell cytoplasm. Saliva from healthy and periodontally diseased patients inhibited P. gingivalis association with the epithelial cells. Attachment to and penetration of gingival epithelial cells by P. gingivalis may be important virulence factors in periodontal disease. Salivary molecules may play a role in modulating these interactions.     

Quantification of PCNA+ cells within odontogenic jaw cyst epithelium

The aim of this study was to investigate the reactivity of the epithelial linings of the three major types of odontogenic cyst with a monoclonal antibody to proliferating cell nuclear antigen (PCNA; clone PC 10). PCNA expression was studied in odontogenic cysts (n=31) and normal oral epithelium (n= 10) using a biotin-streptavidin method on routinely processed paraffin sections. PCNA⁺ cells were counted manually and related to the length of basement membrane (mm) and the epithelial area (mm²) as determined by TV image analysis. The epithelial linings of odontogenic keratocysts (OKC; n= 11) contained the highest number of PCNA⁺ cells, most of which were located in the suprabasal layers. The mean value of PCNA⁺ cells in OKC linings (94.4 ±22.7 cells/mm) was similar to that of oral epithelia (80.8 ± 20.6 cells/mm), but both were significantly higher than that of dentigerous (n = 10. 5.1 ± 3.0 cells mm) and radicular (n = 10, 11.0 ± 4.1 cells /mm) cyst linings (P- 0.005). The epithelial distribution of PCNA⁺ cells differed between groups with the basal/suprabasal PCNA⁺ cell ratio in OKC linings (0.05 ± 0.02) being significantly lower than that of normal oral epithelium (0.5 ± 0.14), dentigerous (l.6 ± 1.23) and radicular (l.9 ± 1.09) cyst linings respectively (P < 0.005). These results demonstrate differences in PCNA⁺ expression between the epithelial linings of the major odontogenic cyst types, indicating differences in proliferative and differentiation processes within these lesions.     

Synergistic enhancement of collagenous protein synthesis by human gingival fibroblasts exposed to nifedipine and interleukin-1-beta in vitro

Abstract: Gingival overgrowth commonly occurs coincident to therapy with calcium channel blockers. The biologic mechanism for this condition is unknown; however, many clinicians suggest that poor oral hygiene may contribute to development of the overgrowth. This study tests the hypothesis that collagenous protein synthesis by gingival fibroblasts is synergistically enhanced when they are exposed to both nifedipine (N) and the pro-inflammatory cytokine, interleukin-1-beta, a cytokine expressed in inflamed gingiva. Human gingival fibroblasts were isolated from biopsies of normal gingiva and cells separated into two groups. Group 1 was exposed to media containing 0, 5, 50, or 500 pg/ml IL-1-beta, or 10⁻⁷ M N for 7 days; Group 2 was exposed to those concentrations of IL-1-beta +10⁻⁷ M N. [³H]-proline was added to the medium for the final 24 h. Cells and matrix were harvested and radioactivity determined by liquid scintillation analysis. Means (d.p.m./10³ cells) were compared by factorial ANOVA and Scheffè comparisons. Collagenous protein synthesis was significantly reduced by 5 pg/ml IL-1-beta +10⁻⁷ M N and enhanced by 500 pg/ml IL-1-beta +10⁻⁷ M N as compared to N or IL-1-beta alone. Thus, patients may be more susceptible to gingival overgrowth coincident to nifedipine therapy as a result of the synergistic enhancement of connective tissue synthesis by these agents.     

Interleukin-1β+3953 allele 2: association with disease status in adult periodontitis

Abstract. Adult periodontitis is a complex multifactorial disease whose etiology is not well defined. The pro-inflammatory and bone resorptive properties of interleukin-1 beta (IL-1β) strongly suggest a role for this cytokine in the pathogenesis of periodontal disease. In the study reported here, the frequency of IL-1β⁺³⁹⁵³ genotypes including allele 2 of the IL-1β⁺³⁹⁵³ restriction fragment length bi-allelic polymorphism was significantly increased in patients with advanced adult periodontitis compared to those with early and moderate disease. Furthermore, allele 2 was associated with increased production of IL-1β by activated peripheral blood polymorphonuclear cells of patients with advanced disease, although this increase failed to reach statistical significance. Finally, the data obtained revealed significant linkage disequilibrium between allele 2 of the IL-1β⁺³⁹⁵³ polymorphism and allele 2 of the bi-allelic IL-1α⁻⁸⁸⁹ polymorphism in both patients and orally healthy controls. These findings provide new insight into the possible role of IL-1α and β gene polymorphisms in the susceptibility to adult periodontitis.     

p53 protein and Ki-67 reactivity in epithelial odontogenic lesions. An immunohistochemical study

Forty-five examples of epithelial odontogenic lesions (9 ameloblastomas (AB): 13 odontogenic keratocysts (OKC): 15 dentigerous cysts (DC): 6 radicular cysts (RC): and 2 odontogenic carcinomas (OC)) were immunohistochemically analyzed for the presence of p53 protein (p53P) and proliferative activity as indicated by positivity for Ki-67 antigen. p53P⁺ cells, detected as dense and/or faint nuclear staining, were found in 42 of the 45 odontogenic lesions examined. Dense p53P reactivity was most commonly detected in OKC, AB and OC, with other lesions generally exhibiting only weak nuclear reactivity. Numbers of Ki-67 positive cells as well as p53P⁺ cells were scored semiquantitatively. Although the presence/absence of densely stained p53P⁺ cells was broadly related to Ki-67⁺ cell numbers, there were no differences in p53P⁺ cell numbers between lesions exhibiting differences in proliferative activity. These results suggest that overexpression of p53P, rather than increased numbers of p53P⁺ cells, is related to proliferation in odontogenic epithelial lesions.