Reduction of epithelial dendritic cells in keratotic lesion of oral lichen planus.

The number and distribution of epithelial dendritic cells (EDC) in oral mucosal lesions are variable depending on the degree of epithelial maturation/differentiation and disease activity. Localized absence of EDC might impair mucosal immunologic protection, allow microbial colonization and enhance carcinogenesis. Increased number of EDC during the early stage of oral lichen planus (OLP) suggests their increased antigen-presenting capability and immunologic activity with inflammatory reaction, but their role in the process of keratinization remains unclear. Therefore, the purpose of this study was to determine the number and distribution of EDC in 33 biopsy specimens from lesions of OLP and from 18 control specimens of leukoplakia (LPL) at sites undergoing increased keratinization. Cells were identified immunocytochemically by the presence of antigen CD68 and labeled with acid phosphatase (AP) and alpha-naphthyl acetate esterase (ANAE) techniques. Numbers of EDC were expressed per mm epithelial surface length. Significantly more EDC with prominent histoenzymatic activity of AP and ANAE were present in OLP than in LPL. Intense enzymatic activity of ANAE was expressed in EDC of OLP with hyperparakeratosis. In the lesions with increased keratinization the number of EDC was markedly reduced in OLP while in LPL remained unchanged. Reduced number and subbasal redistribution of EDC in OLP suggest diminution of immunologic reaction and disease activity but also increased tissue vulnerability to various antigen challenges.