Objectives To compare the numbers of Foxp3⁺ regulatory T cells (Treg) and the proportion of Foxp3⁺ Treg among CD3⁺ T cells and CD4⁺ T cells in oral lichen planus (OLP) in comparison with periodontitis and normal mucosa. Materials and Methods The expression of Foxp3, CD3 and CD4 was examined in 20 biopsied tissues of OLP compared with 20 periodontitis and 10 normal tissues by immunohistochemical method. One-Way ANOVA test was used to compare the numbers of cells expressing Foxp3, CD3 and CD4 and percentages of Foxp3⁺ Treg among CD3⁺ T cells and CD4⁺ T cells at significance level of p<0.05. Results The positive reactivity to CD3, CD4 and Foxp3 were detected in subepithelial mononuclear cells in all cases of OLP, periodontitis and normal healthy mucosa. All of the OLP patients exhibited Foxp3⁺ cells in the lymphocytes at intraepithelium whereas periodontitis and normal healthy subjects were 18 cases (90%) and 8 cases (80%), respectively. The numbers of Foxp3⁺ cells, CD3⁺ T cells and CD4⁺ T cells were statistically different among three groups, in which the highest numbers of the positive cells were found in OLP lesions, periodontitis and normal tissues, respectively. However, the proportions of Foxp3⁺ cells among CD3⁺ T cells or CD4⁺ T cells were not statistically different among three groups. Regarding type of OLP, there were no significant differences in the numbers of CD3⁺ T cells, CD4⁺ T cells and Foxp3⁺ cells and the proportions of Foxp3⁺ cells among CD3⁺ T cells or CD4⁺ T cells between reticular and atrophic/ulcerative OLP. Conclusion The number of Foxp3⁺ Treg significantly increased in OLP lesions, indicating that Foxp3⁺ Treg may play the pivotal role in the immunopathogenesis of OLP.
