IMMUNOHISTOCHEMICAL ANALYSIS OF CHRONIC DISCOID AND SUBACUTE CUTANEOUS LUPUS-ERYTHEMATOSUS - RELATION TO IMMUNOPATHOLOGICAL MECHANISMS

An immunohistochemical analysis of skin biopsies was performed in 18 p atients with cutaneous lupus erythematosus (LE), using the alkaline ph osphatase and monoclonal anti-alkaline phosphatase method (APAAP). The study group was subdivided on the basis of clinical criteria into 10 patients with chronic discoid LE (CDLE) and eight patients with subacu te cutaneous LE (SCLE). Using a panel of monoclonal antibodies the fol lowing results were obtained: (i) ICAM-1 was expressed on epidermal ke ratinocytes, dermal inflammatory cells, and endothelial cells in most biopsies, whereas LFA-1 was confined to the dermis. Attachments betwee n keratinocytes or endothelial cells and activated T lymphocytes via I CAM-1/LFA-1 may be a possible mechanism of target/effector recognition in cutaneous LE. (ii) HLA-DR was expressed on epidermal keratinocytes and cells of the dermal infiltrate, but not on endothelial cells. HLA -DR(+) cells probably function as antigen-presenting cells, leading to major histocompatibility complex-restricted cellular cytotoxicity in cutaneous LE. (iii) Interleukin 2 receptor expression on dermal inflam matory cells was weak, indicating non-specific activation of T lymphoc ytes. (iv) The dermal inflammatory cells were T lymphocytes, mainly of the helper/inducer subtype. B lymphocytes were rarely found in the de rmis. In general, no significant immunohistochemical differences were found between CDLE and SCLE, suggesting that these variants represent clinical subtypes rather than different pathogenetic entities.