Normal human skin was cultured with blister fluid (BF) from 2 patients with epidermolysis bullosa letalis (EB Ietalis). After 12-24 h incubation, initial separation was observed at the dermal-epidermal junction. Complete separation was seen after 48-72 h incubation . Epidermal and dermal structures themselves were well preserved up to 72 h. Electron microscopy revealed that the separation took place through the lamina lu cida. These findings corresponded to in vivo histologic pictures of the

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... n lesions. The activity in BF was lost by lowering (pH 4) or elevating (pH 9) pH of the media or by prolonged autoclaving (5 h).