[Increased expression of adhesion molecules in oral lichen planus]

Adhesion of cells to other cells and to the matrix is the prerequisite for a multitude of cell interactions such as the emigration of circulating leukocytes to sites of inflammation, antigen-presentation, cell-mediated cytotoxicity, cell anchorage and differentiation. In the past few years, a large family of adhesion molecules has been defined which are receptors for these adhesion events. Using immunohistochemical techniques we analyzed the distribution pattern of adhesion molecules in the buccal mucosa of 12 patients with oral lichen planus reticularis and compared it with 12 specimens of normal oral mucosa. In lichen planus, a neo-expression of the antigens VLA-1, 3, 5 and 6, which are receptors for collagen, fibronectin and laminin, could be detected on T cells and macrophages infiltrating the basement membrane zone. ICAM-1, the specific ligand of LFA-1, normally only expressed by endothelial cells, showed a focal expression on basal keratinocytes at sites of intramucosal T cells. The abundance of adhesion molecules on leukocytes and keratinocytes in oral lichen planus is indicative of a special state of activation. It enables the leukocytes to penetrate the tissue, especially the basement membrane zone, to persist in this environment and to exercise their effector functions.