This could be explained by the fact that CD8 cytotoxic T cells are the main cells resulting in keratinocyte apoptosis.13,53 Yang et al. noted that HIV infection depleted the CD4+ regulatory cells (CD4+CD25+), and this resulted in the unregulated activity of the CD8 cytotoxic T cells which resulted in TEN.54 This evidence concerns the gene CD4 and HIV infectious disease.