Macrophage marker 27E10 on human keratinocytes helps to differentiate discoid lupus erythematosus and Jessner's lymphocytic infiltration of the skin

Chronic inflammatory discoid lupus erythematosus (DLE) and Jessner's lympho cytic infiltration of the skin (LIS) are both characterized by dermal infil trates of activated T lymphocytes, However, an inflammatory involvement of the epidermis is only found in DLE, We therefore compared the phenotypic pr operties of the keratinocytes using immunohistochemical stainings of biopsi es from typical DLE and LIS. Keratinocytes failed to express HLA-DR in LIS and surprisingly also in DLE. The adhesion molecule ICAM-1 wan only express ed in DLE, with focal staining of the basal keratinocytes in close associat ion with intraepidermal lymphocytes. The monoclonal antibody 27E10, a disti nct marker for macrophage activation and differentiation. revealed a strong band-like labelling of the suprabasal and upper keratinocytes in DLE. Ln c ontrast, no epidermal expression of this biologically active heterodimer of the calcium-binding proteins MRP-8 and MRP-14 was found in LIS, The staini ng patterns provide a new method to differentiate DLE and LIS by immunohist ochemistry and suggest a distinct type of keratinocyte activation and diffe rentiation in DLE which would in turn mediate epidermal T cell infiltration .