These studies revealed that treating human CD4+ T cells with H2O2 or ONOO− decreased Dnmt1 levels, causing demethylation and overexpression of genes demethylated and overexpressed in CD4+ T cells from patients with active lupus, and that ONOO− was more potent than H2O2, likely reflecting a requirement for O2− to combine with NO to produce ONOO− [10]. Here, DNMT1 is linked to systemic lupus erythematosus.