The pathophysiological study of Fas and FasL on the epidermal cells of TEN patients revealed that an augmentation of soluble FasL (sFasL) and epidermal FasL expression were observed in the sera and skin biopsy specimens from patients with TEN, respectively, suggesting that sFasL detected in the sera is derived from cleavage of a membrane-bound FasL (mFasL) on the epidermal cells of patients with TEN [58]. Here, FAS is linked to toxic epidermal necrolysis.