Expression of Class II transplantation antigens by epithelial cells in oral candidosis, oral lichen planus and gingivitis.

Biopsies from normal oral mucosa and oral mucosa affected by candidosis, lichen planus or gingivitis were compared with respect to the expression of two Class II transplantation antigens, HLA-DR and HLA-DQ, by epithelial cells and the relationship of these antigens to the distribution and frequency of T-lymphocytes. Indirect immunohistochemistry with different mouse monoclonal antibodies was used on frozen and acetone-fixed sections. To evaluate the results, a score system based upon the expression of the Class II transplantation antigens by epithelial cells and the frequency of T-lymphocytes was used. In oral candidosis there was a marked expression of HLA-DR antigens throughout the epithelium. In addition, this type of epithelium was the only one that expressed HLA-DQ antigens. An intense intraepithelial infiltration of T-lymphocytes was observed. Oral lichen planus and gingivitis did, to a much lesser extent, cause the expression HLA-DR antigens by the epithelial cells. In both lesions, the number of T-lymphocytes within the epithelium did not exceed the number found in epithelium of normal mucosa. In these types of lesions, the subepithelial infiltrate varied in intensity but was mainly composed of T-lymphocytes reactive with anti-Leu 3a antibodies. The results of the present study imply that epithelial expression of the two different Class II antigens are related to the frequency of the T-lymphocytes and to the proximity of these cells to the epithelial cells.