Distribution of Merkel cells in acute UVB erythema.

Merkel cells (MC) were identified immunohistochemically using antibodies specific for cytokeratin (CK) 20 within human epidermis 12 to 72 h after exposure to UVB (4 MED). 12 h after exposure all MC were normally localized within the epidermal basal layer. However, 24 h after exposure 4% of the MC were detected suprabasally, the remaining 96% still being situated in the basal layer. Surprisingly, at 48 h and 72 h more than 50% had lost contact with the basal membrane. The MC of hair follicles did not show any obvious changes. These results argue, in the context of acute epidermal UV damage, for an abnormal turnover in dermatitis.