Merkel cells do not express bullous pemphigoid antigen.

Merkel cells (MC) are epithelial cells expressing cytokeratin-type intermediate filaments. They often are localized within the basal cell layer of the epidermis. Since basal cell layer keratinocytes synthetize basal membrane components, it was of interest to investigate whether or not MC could also do so. We used both double-labeling immunofluorescence and immune electron microscopy techniques with a panel of antibodies allowing the identification of MC as well as the staining of basal membrane zone components (including bullous pemphigoid antigen, laminin, type IV collagen and epidermolysis bullosa antigen). A specific loss of BP antigen expression was observed below all MC directly in contact with BMZ. This suggests that, although being an epithelial cell and in contrast to basal keratinocytes, MC does not secrete BP antigens.