In the severe types of drug eruption, cytotoxic immune cells, such as CD8+ T cells, NK cells, and NKT cells identify the specific epitopes HLA-drug interaction and produce cytotoxic proteins such as Fas ligand, perforin, granzyme B, and granulysin and provoke epidermal keratinocyte cell death, which is associated with the severe clinical manifestation of SJS/TEN. The gene discussed is GNLY; the disease is toxic epidermal necrolysis.