GP37 expression in normal and diseased human epidermis: a marker for keratinocyte differentiation.

An antiserum prepared against a glycoprotein (GP37) extracted from the upper epidermal layers, was used to stain frozen sections of human oral mucosa, normal and abnormal skin by an indirect immunofluorescence technique. On normal human epidermis, this antiserum mainly reacted with the cytoplasm of granular cells, whereas on buccal mucosa the recognized antigen was observed as scattered dots limited to the upper epithelial layers. In epidermal diseases, alterations in the staining pattern were observed. In psoriasis, the labelling was markedly diminished; in contrast, in lichen planus it was intense and present on the 3-6 uppermost cellular layers. Basal cell epitheliomas were almost negative, except around horn cysts. In Bowen's disease dyskeratotic cells were strongly labelled. In squamous cell carcinomas a clear-cut staining was observed in squamous nests. On cultures, GP37 expression could be induced by growing epidermal cells in vitamin A-depleted medium. The biological significance of the observed staining patterns remains to be precised. Nevertheless, GP37 represents a sensitive marker of epidermal differentiation and may be useful in skin pathology and in in vitro studies.