Numerous reports on the immunopathogenesis of an oral lichen planus (OLP) have shown some inconsistency in terms of the role and distribution of CD4+ and CD8+ T cells, and Langerhans cells (LC). This has led to the hypothesis that although the clinical and histopathological manifestations of OLPs appear similar, they can be grouped into CD4+ predominant lesions and CD8+ ones on the varied immunopathogenesis or clinical progress. This study investigated the distribution of CD4+ T cells, CD8+ T cells, LC and the ratio of CD4/CD8 and defined the important immunocompetent cells. In addition, the clinicopathological and histopathological correlation with those immunocompetent cells were investigated. Frozen sections of 16 OLPs and 5 normal buccal mucosae were immunostained. Quantification was done using KAPPA Imagebase software and statistical analysis using SPSS 10.0 statistical package. CD8+ T cells were consistently more abundant in the epithelium of the OLP than CD4+ T cells, but no difference between the two cells was detected in the lamina propria. The intra-epithelial CD4+ T cells revealed a positive linear correlation with the intra-epithelial CD8+ T cells. In the lamina propria, the number of LC had a positive linear correlation with CD4/CD8 ratio. The number of LCs was higher in the reticular type of OLP compared to the erosive type. The histopathological features such as hyperkeratosis, acanthosis, the band-like infiltration of mononuclear cells, and liquefaction degeneration did not show significant correlation with the CD4/CD8 ratio. The results suggest that CD8+ T cells play major role in immunopathogenesis of OLP. The immunopathogenesis of OLP appears to vary from lesion to lesion in relation to the clinical progress.

Ⅰ. Introduction
 II. Materials and Methods
  1. Tissue specimens
  2. Immunohistochemistry
  3. Quantification
  4. Histopathologic examination
  5. Statistical analysis
 III. Results
  1. The expressions of CD4, CD8, and CD1a inOLP
  2. Correlation between the ratio of CD4/CD8and the number of Langerhans cells in OLPs
  3. Comparison of the infiltration of immune cellsaccording to clinical features of OLPs
  4. Comparison of the CD4/CD8 ratio accordingto histopathological parameters of OLPs
 IV. Discussion
 V. References

• 김수진(Department of Oral Pathology, School of Dentistry, Seoul National University) | Soo Jin Kim
• 조영아(Department of Oral Pathology, School of Dentistry, Seoul National University) | Young Ah Cho
• 윤혜정(Department of Oral Pathology, School of Dentistry, Seoul National University) | Hye Jung Yoon
• 홍성두(Department of Oral Pathology, School of Dentistry, Seoul National University) | Seong Doo Hong
• 이재일(Department of Oral Pathology, School of Dentistry, Seoul National University) | Jae Il Lee
• 홍삼표(Department of Oral Pathology, School of Dentistry, Seoul National University) | 홍샴표 correspondence