Immunopathological aspects of etretinate therapy in lichen planus

Biopsy specimens of involved and uninvolved skin were studied in 8 patients suffering from generalized lichen planus (LP) before and after successful etretinate treatment using murine monoclonal antibodies against several cell surface markers of effector and/or accessory cells of the immune system. In contrast to untreated LP-lesions, in biopsies obtained after etretinate therapy from healed involved skin a markedly disintegrated HLA-DR expression on keratinocytes and intraepidermal Langerhans cells and a nearly total loss of suppressor/cytotoxic T lymphocytes at the dermo-epidermal interface were found. Our data emphasize the key position of the class II antigen expression on various immunocompetent cells, as a marker for a cell-mediated immune reaction, on the other hand, stress the involvement of keratinocytes, Langerhans cells and suppressor/cytotoxic T lymphocytes in the pathogenesis of LP.