Assessment of Langerhans' cells in oral lichen planus using monoclonal antibodies.

In order to demonstrate Langerhans' cells in epithelium of oral lichen planus, monoclonal antibodies were used as immunological markers in combination with immunohistochemistry. By the use of anti-Ia antibodies the Langerhans' cells were shown to express an increased number of Ia-like antigens in comparison to the amounts found in healthy oral mucosa. The subepithelial infiltrate of mononuclear cells expressed identical Ia-like antigens on their surfaces. With anti-T6 antibodies as immunological markers, the number of Langerhans' cells was found to be virtually identical in diseased and healthy epithelium. Treatment of oral lichen planus with tretinoin resulted in a decrease of epithelial Ia-like antigens compared with the number found in untreated lesions. However, treatment with tretinoin did not alter the frequency of Langerhans' cell marked with anti-T6 antibodies. The present data demonstrate an increased amount of Ia-like antigens per number of T6-positive Langerhans' cells in diseased oral mucosa compared to healthy conditions. The increased expression of Ia-like antigens on Langerhans' cells and the contemporary finding of Ia-like antigens on the subepithelial T-cells support the opinion that the pathogenesis of oral lichen planus is mainly a cell-mediated type of immunological reaction.