The genes encoding perforin (PRF1), CD11a (ITGAL), CD70 (TNFSF7), CD40L (CD40LG), and the killer cell immunoglobulin-like receptor (KIR) genes are normally suppressed by DNA methylation in CD4+ T cells, but are demethylated and over-expressed by CD4+ T cells from patients with active lupus [5,6]. Here, PRF1 is linked to systemic lupus erythematosus.