PRF1 and toxic epidermal necrolysis: While the cytotoxic molecules Fas, FasL, perforin, and granzyme B did not differ between the two conditions, the number of intraepidermal cells expressing granulysin, which is known to be a major mediator of epidermal necrosis in SJS/TEN, was shown to be significantly greater in SJS/TEN than GBFDE [32].