CD4 and rheumatoid arthritis: AUC, sensitivity and specificity of IFI44L methylation (especially with all DMS found on the gene) for RA and SLE compared with matched controls in CD4+ T cells are particularly high, demonstrating that RA and SLE patients can be well discriminated from healthy controls through the methylation differences in IFI44L. Our finding for SLE is also in line with a previous biomarker study conducted in SLE peripheral blood (Zhao et al., 2016), which provides further proof for the diagnostic value of IFI44L.