Prolonged Suppressive Effects of Periodontitis on Salivary TFF3 Production

Objective As a follow-up to our previous study that demonstrated decreased salivary trefoil factor family 3 (TFF3) peptide levels in chronic periodontitis patients, this current study aimed to observe the effects of nonsurgical periodontal treatment on salivary TFF3 peptides in patients with periodontal diseases.

Materials and Methods Eighty-seven volunteers that comprised of 30 individuals with healthy periodontium, 31 with gingivitis, and 26 with chronic periodontitis were considered for the study. Prior to periodontal treatment, a general periodontal examination was performed along with collection of saliva samples from each volunteer. Nonsurgical periodontal treatments were provided to patients with gingivitis and periodontitis. Two weeks post-treatment, saliva samples were recollected, and the periodontal status was re-evaluated. Salivary TFF3 concentrations were measured by enzyme-linked immunosorbent assay.

Statistical Analysis Mann–Whitney U test was used when the investigated data were not normally distributed. Chi-squared test was used when dealing with categorical data. Kruskal–Wallis test with post-hoc corrections was used to compare data among the three investigated groups. Two-tailed p < 0.05 was considered as statistically significant.

Results Prior to the periodontal treatment, salivary TFF3 concentrations in patients with gingivitis and periodontitis were significantly lower than those with healthy periodontium. Two weeks post-treatment, increased levels of salivary TFF3 were observed in patients with gingivitis, whereas the concentrations decreased in patients with chronic periodontitis.

Conclusion This study demonstrated the effects of periodontal disease on the production of salivary TFF3 peptides. Interestingly, nonsurgical periodontal treatment also affected the recovery of salivary TFF3 peptides but varied in their outcomes between gingivitis and periodontitis patients.

Serum cell-free DNA methylation of OPCML and HOXD9 as a biomarker that may aid in differential diagnosis between cholangiocarcinoma and other biliary diseases

BACKGROUND

Cholangiocarcinoma (CCA) is a fatal cancer of the bile duct epithelial cell lining. The misdiagnosis of CCA and other biliary diseases may occur due to the similarity of clinical manifestations and blood tests resulting in inappropriate or delayed treatment. Thus, an accurate and less-invasive method for differentiating CCA from other biliary diseases is inevitable.

METHODS

We quantified methylation of OPCML, HOXA9, and HOXD9 in serum cell-free DNA (cfDNA) of CCA patients and other biliary diseases using methylation-sensitive high-resolution melting (MS-HRM). Their potency as differential biomarkers between CCA and other biliary diseases was also evaluated by using receiver operating characteristic (ROC) curves.

RESULTS

The significant difference of methylation levels of OPCML and HOXD9 was observed in serum cfDNA of CCA compared to other biliary diseases. Assessment of serum cfDNA methylation of OPCML and HOXD9 as differential biomarkers of CCA and other biliary diseases showed the area under curve (AUC) of 0.850 (0.759-0.941) for OPCML which sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy were 80.00%, 90.00%, 88.88%, 81.81%, and 85.00%, respectively. The AUC of HOXD9 was 0.789 (0.686-0.892) with sensitivity, specificity, PPV, NPV, and accuracy of 67.50%, 90.00%, 87.09%, 73.46%, and 78.75%, respectively. The combined marker between OPCML and HOXD9 showed sensitivity, specificity, PPV, and NPV of 62.50%, 100%, 100%, and 72.72%, respectively, which may be helpful to prevent a misdiagnosis between CCA and other biliary diseases.

CONCLUSIONS

Our findings suggest the application of serum cfDNA methylation of OPCML and HOXD9 for differential diagnosis of CCA and other biliary diseases due to its less invasiveness and clinically practical method which may benefit the patients by preventing the misdiagnosis of CCA and avoiding unnecessary surgical intervention.

Effects of arecoline on proliferation of oral squamous cell carcinoma cells by dysregulating c-Myc and miR-22, directly targeting oncostatin M

Arecoline, the major alkaloid of areca nut, is known to induce oral carcinogenesis, however, its mechanism is still needed to elucidate. This study investigated the effects of arecoline on cell viability and cell-cycle progression of oral squamous cell carcinoma (OSCC) cells as well as a relevant cellular gene expression. The results showed that a low concentration of arecoline (0.025 μg/ml) increased OSCC cell viability, proportion of cells in G2/M phase and cell proliferation. Simultaneously, it induced IL-6, STAT3 and c-Myc expression. Interestingly, c-myc promoter activity was also induced by arecoline. MiR-22 expression in arecoline-treated OSCC cells was suppressed and comparable to an upregulated c-Myc expression. In arecoline-treated OSCC cells, oncostatin M (OSM) expression was significantly upregulated and inversely correlated with miR-22 expression. Likewise, OSM expression and its post-transcriptional activity were significantly decreased in miR-22-transfected OSCC and 293FT cells. This result demonstrated that miR-22 directly targeted OSM. Interestingly, miR-22 played an important role as a tumor suppresser on suppressing cell proliferation, migration and cell-cycle progression of OSCC cells. This result suggested the effect of arecoline to promote cell proliferation and cell-cycle progression of OSCC cells might be involved in induction of c-Myc expression and reduction of miR-22 resulting in OSM upregulation.

New evidence of connections between increased O-GlcNAcylation and inflammasome in the oral mucosa of patients with oral lichen planus

Oral lichen planus (OLP) is considered a chronic inflammatory immune-mediated disease of the oral mucosa. Immunopathogenesis of OLP is thought to be associated with cell-mediated immune dysregulation. O-GlcNAcylation is a form of reversible glycosylation. It has been demonstrated that O-GlcNAcylation promoted nuclear factor kappa B (NF-κB) signalling. Activation of NF-кB can induce expression of nucleotide-binding domain-like receptor family pyrin domain containing 3 (NLRP3) inflammasome, which is a large intracellular multi-protein complex involving an immune response. Dysregulated expression of the NLRP3 inflammasome was reported to be associated with autoinflammatory diseases. No integrative studies between O-GlcNAcylation and NLRP3 inflammasome in OLP patients have been reported. The present study aimed to determine the immunohistochemical expression of O-GlcNAcylation, NF-κB signalling molecules and NLRP3 inflammasome in oral mucosae of OLP patients. Oral tissue samples were collected from 30 OLP patients and 30 healthy individuals. Immunohistochemical staining and analyses of immunostaining scores were performed to evaluate expression of O-GlcNAcylation, NF-κB signalling molecules and NLRP3 inflammasome. According to observations in this study, significantly higher levels of O-GlcNAcylation, NF-κB signalling molecules and NLRP3 inflammasome were demonstrated in OLP patients compared with control subjects (P < 0·001). Positive correlations among O-GlcNAcylation, NF-κB signalling molecules and NLRP3 inflammasome were also observed in OLP samples (P < 0·01). In conclusion, the present study provides supportive evidence that increased O-GlcNAcylation is associated with increased expression of NLRP3 inflammasome via the NF-κB signalling pathway. These findings provide a new perspective on immunopathogenesis of OLP in relation to autoinflammation.

Production of Monoclonal Antibodies against Human Trefoil Factor 3 and Development of a Modified-Sandwich ELISA for Detection of Trefoil Factor 3 Homodimer in Saliva

Background

Human trefoil factor (TFF) peptides consist of three members: TFF1, TFF2 and TFF3. TFF3 is the most abundant TFF peptide in saliva. TFF3 homodimer was suggested to be involved in apoptosis inhibition and malignancy. Determination of TFF3 homodimer expression profiles in saliva may lead to new information about oral biology and diseases. The objective of this study was to generate monoclonal antibodies (mAbs) against TFF3 and apply the produced mAbs for the establishment of ELISA for quantification of dimeric TFF3 in saliva.

Results

With our modified hybridoma technique, three hybridoma clones producing anti-TFF3 mAbs having IgG isotype were generated. The mAbs were specific for TFF3 with no cross-reactivity to other TFFs. Using the generated mAbs, a modified-sandwich ELISA with high sensitivity for the quantification of dimeric TFF3 in saliva was developed. Using this ELISA, the amount of dimeric TFF3 in saliva could be measured.

Conclusions

A modified-sandwich ELISA for the quantification of TFF3 dimeric form was established. The established ELISA will be a valuable tool for facilitating the investigation of the physiological roles and the diagnostic values of TFF3 in oral diseases. The concept of this modified-sandwich ELISA may be applied for the determination of other homodimeric peptides of interest.

Proteolytic effects of gingipains on trefoil factor family peptides

OBJECTIVES

The present study was aimed to determine whether trefoil factor family (TFF) peptides which were generally considered to be resistant to proteolysis could be digested by gingipains, a major proteinases produced by Porphyromonas gingivalis.

MATERIALS AND METHODS

Recombinant human TFF1, TFF2, and TFF3 peptides were used as substrates. Gingipains including arginine gingipain (RgpB) and lysine gingipain (Kgp) were used as enzymes. Trypsin was used as a control protease. Matrix-assisted laser desorption/ionization with time-of-flight / time-of-flight (MALDI-TOF/TOF) and liquid chromatography mass spectrometry (LC-MS) were used for analyzing peptide mass signals and amino acid sequences of digested TFF peptides.

RESULTS

MALDI-TOF/TOF analyses demonstrated that Kgp, RgpB, and trypsin were able to cleave TFF1 and TFF2 peptides, resulting in different patterns of digested fragments. However, impurity in recombinant TFF3 peptide substrates affected the interpretations of enzymatic reaction by MALDI-TOF/TOF. LC-MS analyses demonstrated that identified fragments of TFF1, TFF2, and TFF3 from digestion by gingipains were similar to those by trypsin.

CONCLUSIONS

Using MALDI-TOF/TOF and LC-MS, the present study provides new information that gingipains containing trypsin-like activities are able to digest TFF peptides.

CLINICAL RELEVANCE

The proteolytic effects of gingipains on TFF peptides may be responsible for reduction of salivary TFF peptides in chronic periodontitis patients. Further investigations to determine the pathological effects of gingipains on TFF peptides in saliva and periodontal tissues of patients with chronic periodontitis would be of interest.

The anti-oxidant effects of melatonin derivatives on human gingival fibroblasts

OBJECTIVES

Aim of this in vitro study was to evaluate the anti-oxidant activity of indole ring modified melatonin derivatives as compared with melatonin in primary human gingival fibroblast (HGF) cells.

METHODS

Anti-oxidant activity of melatonin (MLT), acetyl-melatonin (AMLT) and benzoyl-melatonin (BMLT) was evaluated by5 standard methods as follows: 2, 2-diphenyl-1-picrylhydrazyl (DPPH); ferric ion reducing antioxidant power (FRAP); superoxide anion scavenging; nitric oxide (NO) scavenging; and thiobarbituric acid reactive substances (TBARs).Evaluation of cellular antioxidant activity (CAA) and protectivity against H₂O₂ induced cellular damage was performed via MTT assay in HGF cells.

RESULTS

According to the standard anti-oxidant assays, the antioxidant power of AMLT and BMLT were slightly less than MLT in FRAP and superoxide scavenging assays. In the NO scavenging and TBARs assays, BMLT and AMLT were more potent than MLT, whereas DPPH assays demonstrated that MLT was more potent than others. BMLT and AMLT had more potent anti-oxidant and protective activities against H₂O₂in HGF cells as compared with MLT.

CONCLUSIONS

MLT derivatives demonstrated different anti-oxidant activities as compared with MLT, depending upon assays. These findings imply that N-indole substitution of MLT may help to improve hydrogen atom transfer to free radicals but electron transfer property is slightly decreased. Anti-oxidant and protective effects of melatonin derivatives (AMLT and BMLT) on human gingival fibroblasts imply the potential use of these molecules as alternative therapeutics for chronic inflammatory oral diseases.

Increased melatonin in oral mucosal tissue of oral lichen planus (OLP) patients: A possible link between melatonin and its role in oral mucosal inflammation

OBJECTIVE

The existence of extra-pineal melatonin has been observed in various tissues. No prior studies of melatonin in human oral mucosal tissue under the condition of chronic inflammation have been reported. The aim of this study was to investigate the presence of melatonin in oral mucosal tissue of patients with oral lichen planus (OLP) which was considered as a chronic inflammatory immune-mediated disease causing oral mucosal damage and ulcerations.

MATERIALS AND METHODS

Sections from formalin-fixed and paraffin-embedded oral mucosal tissue of OLP patients (n=30), and control subjects (n=30) were used in this study. Immunohistochemical staining was performed and the semiquantitative scoring system was used to assess the levels of arylalkylamine-N-acetyltransferase (AANAT: a rate-limiting enzyme in the biosynthesis pathway of melatonin), melatonin, and melatonin receptor 1 (MT1) in oral mucosa of OLP patients and normal oral mucosa of control subjects.

RESULTS

AANAT, melatonin, and MT1were detected in oral mucosal tissue of OLP patients and control subjects. Immunostaining scores of AANAT, melatonin, and MT1 in oral mucosal tissue of OLP patients were significantly higher than those in control subjects (p=0.002, p<0.001, and p=0.031, respectively).

CONCLUSIONS

Increased levels of AANAT, melatonin, and MT1 in the inflamed oral mucosal tissue of OLP patients imply that chronic inflammation may induce the local biosynthesis of melatonin via AANAT, and may enhance the action of melatonin via MT1.

Monitoring the biochemical alterations in hypertension affected salivary gland tissues using Fourier transform infrared hyperspectral imaging

FTIR imaging shows biochemical differences between salivary glands from control and hypertensive rats.

Effect of human papillomavirus 16 oncoproteins on oncostatin M upregulation in oral squamous cell carcinoma

Human papillomavirus (HPV) infection modulates several host cytokines contributing to cancer development. Oncostatin M (OSM), an IL-6 family cytokine, acts to promote cell senescence and inhibit growth. Its dysregulation promotes cell survival, cell proliferation and metastasis in various malignancies. The effect of HPV on OSM dysregulation has not been investigated. To elucidate this, immunohistochemistry was used on formalin-fixed, paraffin-embedded oral squamous cell carcinoma (OSCC) tissues: HPV-positive (50) and HPV-negative (50) cases. Immortalized human cervical keratinocytes expressing HPV16E6 (HCK1T, Tet-On system) were used to demonstrate the role of HPV16E6 in OSM expression. In addition, a vector containing HPV16E6/E7 was transiently transfected into oral cancer cell lines. Cell viability, cell-cycle progression and cell migration were evaluated using flow cytometry and a wound healing assay, respectively. The results showed various intensities of OSM expression in OSCC. Interestingly, the median percentages of strongly stained cells were significantly higher in HPV-positive OSCCs than in HPV-negative OSCCs. To explore the role of HPV oncoproteins on OSM expression, the expression of HPV16E6 in the HCK1T Tet-On condition was induced by doxycycline and HPV16E6 was found to significantly upregulate levels of OSM mRNA and protein, with concomitant upregulation of c-Myc. In addition, the levels of OSM mRNA and protein in E6/E7 transiently transfected oral cancer cells also gradually increased in a time-dependent manner and these transfected cells showed greater viability and higher migration rates and cell-cycle progression than controls. This result demonstrates that HPV16 oncoproteins upregulate OSM and play an important role to promote OSCC development.

Brief communication (Original). Trefoil factor expression by immunohistochemistry in patients with oral lichen planus

Background: Oral lichen planus (OLP) is a chronic immune-mediated inflammatory disease that usually causes oral mucosal damage. OLP has been considered to be a potentially malignant disorder associated with an increased risk for oral cancer. Trefoil factors (TFFs) are mainly synthesized by mucin-producing epithelial cells. Expression of TFFs in oral epithelia is thought to be an essential factor in protection against oral mucosal damage. However, very little is known about the connection between tissue damage of oral mucosa in OLP patients and expression of TFFs.

Objectives: To determine levels of TFF expression in oral mucosa from patients with OLP.

Methods: Tissue samples were collected from 35 patients with normal oral mucosa (controls) and 35 patients with OLP. An immunohistochemical method was used to determine the expression of the 3 TFFs (TFF1, 2, and 3) in mucosal tissues of the oral cavity.

Results:TFF2 and TFF3 expression in oral epithelia were significantly decreased in OLP patients (Mann- Whitney U test; P = 0.006, and P = 0.002, respectively). There were no significant differences in TFF1 expression between OLP patients and control subjects.

Conclusion: The present study demonstrated reduced expression of TFF2 and TFF3 in oral epithelia of OLP patients. These outcomes support our previous observations that chronic inflammation may play a major role in downregulation of TFF expression, which may be associated with oral mucosal damage in OLP patients.

Trefoil factor family peptides in human saliva and cyclical cervical mucus. Method evaluation and results on healthy individuals

BACKGROUND

Trefoil peptides are 7-12 kDa molecules, se-creted by a variety of mucin-producing epithelial cells from different tissues and believed to be essential for protection and maintenance of gastrointestinal mucosa. Data on concentrations of trefoil peptides in secretions are limited.

METHODS

We validated in-house ELISA assays, developed for measurement of trefoil peptide concentrations (TFF1, TFF2 and TFF3) in serum, for use with saliva and cervical mucus. Saliva from healthy individuals (n=30), and cervical mucus as well as blood collected three times during the menstrual cycle from healthy women (n=18) were analyzed.

RESULTS

Recovery of all trefoil peptides in the initial supernatants of saliva and (cervical mucus) were 86 and (92)% or more. Recovery of exogenously added trefoil peptides was 93 and (95)% or more. Western blotting showed that antibodies used in the TFF3-ELISA assay recognised one molecule of the same size as TFF3 in both saliva and cervical mucus. Median concentrations of TFF1, TFF2 and TFF3 in saliva and (cervical mucus) were 2.7 (2.7), 0.08 (0.58) and 14 (430) nmol/g protein, with a significant decrease in concentrations in cervical mucus after ovulation. Serum concentrations resembled previously measured values in blood donors and showed no cyclic change.

CONCLUSIONS

Previously established ELISA assays can be employed for measurement of trefoil peptides in saliva and cervical mucus. TFF3 was the predominant trefoil peptide in both saliva and cervical mucus, and TFF3 in cervical mucus represents the highest concentration measured in a biological fluid to date.

Alteration of the expression of CD44 [corrected] isoforms in oral epithelia and saliva from patients with oral lichen planus

Oral lichen planus (OLP) is a chronic inflammatory mucosal disease that cell-mediated immunological mechanisms are involved in pathogenesis. The objective of this study was to investigate the expression of CD44 isoforms including CD44s, CD44v5, and CD44v6 in biopsy specimens and saliva from OLP patients. Thirty-one OLP patients and 30 healthy subjects were enrolled in this study. Immunohistochemical methods were used to detect the expression of CD44 isoforms in oral epithelia, and enzyme-linked immunosorbent assay (ELISA) was performed to measure levels of salivary CD44 isoforms. Our results demonstrated that expression of CD44v6 in oral epithelia from OLP patients was significantly decreased in comparison to controls (p = 0.021). Levels of salivary CD44s and CD44v5 from OLP patients were significantly higher than those from controls (p = 0.007 and p = 0.002, respectively). In summary, our findings provided additional evidence that the pathological stress, such as chronic inflammation, altered the expression of CD44 isoforms in oral epithelia and saliva of OLP patients.

Expression of TNF-alpha in oral lichen planus treated with fluocinolone acetonide 0.1%

BACKGROUND

Oral lichen planus (OLP) is a common chronic inflammatory disease involving T cells-mediated immunity. Tumor necrosis factor (TNF)-alpha has been reported to be involved in the disease process. The purpose of this study was to investigate the effect of fluocinolone acetonide in orabase (FAO) 0.1% on the expression of TNF-alpha in patients with OLP.

METHODS

Eighteen Thai patients with atrophic or erosive OLP were recruited. Biopsy specimens were taken before and 1 month after treatment with FAO 0.1% and sent for histopathologic examination where they were immunohistochemically stained with antibody to TNF-alpha. Twenty normal mucosa specimens were identically processed. Oral squamous cell carcinoma tissue was used as a positive control for TNF-alpha expression, whereas OLP sections without primary antibody were served as negative control.

RESULTS

Sixteen of 18 cases (88.89%) of OLP exhibited positive staining for TNF-alpha. Most of the TNF-alpha was observed in the mononuclear cells. Ten cases (55.56%) of OLP demonstrated TNF-alpha expression in keratinocytes. The number of mononuclear cells positive for TNF-alpha before the treatment with FAO 0.1% in orabase was statistically higher than that after the treatment (P=0.000) and in the normal mucosa (P=0.000). Moreover, the number of mononuclear cells after treatment with FAO 0.1% in orabase was statistically lower than before the treatment (P=0.000).

CONCLUSION

Our study exhibited that TNF-alpha may be associated with the immunopathogenesis of OLP in Thai patients and FAO 0.1% had an effect on the reduction of TNF-alpha expression.

Nitrative and oxidative DNA damage in oral lichen planus in relation to human oral carcinogenesis

Oral lichen planus (OLP) is a chronic inflammatory disease, which has been clinically associated with development to oral cancer. A double immunofluorescence labeling study found that 8-nitroguanine and 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) accumulated in oral epithelium in OLP and oral squamous cell carcinoma (OSCC) biopsy specimens, whereas little or no immunoreactivity was observed in normal oral mucosa. Colocalization of 8-nitroguanine and inducible nitric oxide synthase (iNOS) was found in oral epithelium of OLP and OSCC. Immunoreactivity of 3-nitrotyrosine, which is formed by protein tyrosine nitration and is considered to be a biochemical marker for inflammation, was also observed in oral epithelial cells and colocalized with 8-nitroguanine. Accumulation of p53 was more strongly observed in oral epithelium in OSCC than OLP, whereas there was no p53 accumulation in normal oral mucosa. Our findings demonstrate that iNOS-dependent DNA damage in OLP may lead to p53 accumulation in not only OLP but also OSCC. We conclude that the formation of potentially mutagenic DNA lesions including 8-nitroguanine and 8-oxodG may contribute to the development of oral cancer from OLP.

Measurements of HIV viral loads from different levels of the respiratory tract

BACKGROUND

The lung is a common site of disease in HIV infection. Virus has been detected in BAL fluid (BALF) and saliva. However, the relationship between viral loads detected at different levels of the respiratory tract is unknown.

METHOD

We measured simultaneous HIV viral loads in parotid saliva (PS), bronchial fluid (BF), BALF, and plasma by reverse transcription polymerase chain reaction in 20 HIV-infected individuals.

RESULTS

HIV was detected in 53% of BALF samples, 15% of BF samples, 5% of PS samples, and 88% of plasma samples. Viral loads in plasma and BALF samples were positively correlated. There were significantly higher levels of HIV viral load in both plasma and BALF in subjects with CD4 counts of < 200 cells/ microL compared to those with higher counts. Antiretroviral therapy (ART) was associated with lower BALF and plasma viral loads, and the effect in BALF was independent of the plasma viral load. Interestingly, smoking also was associated with lower levels of both BAL and BF viral loads, independent of the plasma viral load.

CONCLUSION

These data demonstrate that while HIV can be detected in the respiratory tract, the viral load is influenced by both local factors (ie, level of the respiratory tree and cigarette smoking) and systemic factors (ie, ART and peripheral CD4 count).

Salivary immunoglobulin A antibodies to gp41 in human immunodeficiency virus-seropositive patients: lack of correlation with disease progression

Mucous membranes are the main route of transmission of human immunodeficiency virus (HIV). Interestingly, some viral inhibitory activities have been found in saliva. The purpose of this study was to determine the level of salivary immunoglobulin A (IgA) antibodies to gp41 in HIV+ patients at various disease stages to identify whether gp41 was able to induce vigorous humoral responses. Unstimulated saliva samples were obtained from three groups of subjects (n=37): group A (HIV-), group B (HIV+, CD4+ <200/mm3), and group C (HIV+, CD4+ >200/mm3). IgA antibody levels to purified gp41 were determined by enzyme-linked immunosorbent assay (ELISA). Western blot analyses were performed using HIV+ saliva to confirm IgA reactivity to gp41. ELISA demonstrated that HIV+ subjects had higher IgA antibody to gp41 than HIV- individuals. No significant differences were noted between HIV+, CD4+ <200/mm3 and CD4+ >200/mm3 subjects. High (81.25%) IgA reactivity to gp41 was demonstrated by Western blotting of saliva from all HIV+ individuals. In conclusion, gp41 responses are important in the HIV disease process, as indicated by the high IgA levels and gp41 reactivity in saliva of HIV+ patients.

Oral lichen planus: an immunohistochemical study of heat shock proteins (HSPs) and cytokeratins (CKs) and a unifying hypothesis of pathogenesis

The expression of heat shock proteins HSP60 and HSP70 and cytokeratins CK1/10 and CK7/18 were compared in epithelium of oral lichen planus (OLP) lesions and oral fibromas using an avidin-biotin-peroxidase complex (ABC) immunohistochemical method. An immunostaining intensity distribution (IID) index was developed to assess staining intensity and the proportion of positively stained cells in different layers of the epithelium. The expression of HSP60 in the basal layer was significantly higher in OLP than in fibromas. No difference in HSP70 expression was evident between OLP and fibromas. The expression of CK1/10 in the epithelial basal and suprabasal layers was significantly higher in OLP than in fibromas. There was no demonstrable staining for CK7/18 in either OLP or fibromas. A significant correlation was evident between the expression of HSP60 and CK1/10 in the basal epithelial cells in OLP. The findings support a role for HSP60 in the pathogenesis of OLP. A unifying hypothesis of the pathogenesis of OLP, involving two sequential immune reactions, is proposed.