Keratin expression in discoid lupus erythematosus

21 lesions from 16 patients with discoid lupus erythematosus (DLE) were examined immunohistologically using monoclonal antibodies to keratins (K). Markers of basal epithelial cells (the keratin conformation specific basal markers LH6 and LH8), differentiating keratinocytes (K1 and K10), hyperproliferating keratinocytes (K16) and panepidermal keratin (K14), were used. A monoclonal antibody to type VII collagen was used as a guide to the state of the basement membrane zone (BMZ). Keratin distribution in DLE differed from controls. Suprabasal cells were labelled by LH6 in 95% of specimens (19/20) and LH8 in 79% (15/19) in contrast to the basal distribution in normal skin. Reduction of suprabasal LL017 (K1) expression was seen in 59% (10/17) of lesions. An increase of LL025 (K16) expression was seen in 33% (5/15) of specimens. Where LL025 (K16) expression was increased, LL017 (K1) expression was reduced in 80% (4/5). Dermal colloid bodies expressed both basal and suprabasal keratins and were present at sites of maximal basement membrane disruption. These findings are consistent with a model of DLE in which there is an increase in the proliferative basal compartment. This compartment and the associated BMZ suffer fragmentation and loss of colloid bodies to the dermis which express a range of keratins not uniformly associated with basal keratinocytes.