Animal models of toxic epidermal necrolysis.

Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are severe acute exfoliative skin diseases developing extensive epidermal detachment and mucosal damage. Although SJS and TEN are mostly caused by drugs, an animal model of TEN using drugs has not been established yet. We have established an autoimmune skin disease model mouse reproducing the devastating skin damage of TEN by a combination of transgenic mice expressing an epidermal model antigen and its specific CD8(+) T-cell receptor. In this model mouse, we found that the thymus-derived CD4(+) CD25(+) regulatory T cell (Treg) is a critical regulator of cytotoxic T lymphocytes (CTL) causing TEN. Indeed, loss of Treg function was recently demonstrated by human studies of TEN patients. Although how drug-reactive CTL is activated in vivo is still unknown, this model elucidated the immunological pathomechanism of TEN after CTL obtained cytotoxicity against epidermal keratinocyte. In this review, roles of CTL, Treg, cytotoxic granules and antigen-presenting cells were discussed on pathogenesis of TEN.