CD4 and rheumatoid arthritis: In this study, we investigated DNA methylation using reduced representation bisulfite sequencing in two CD4+ T cell populations (CD4+ memory and naïve cells) in three groups: newly diagnosed, disease modifying antirheumatic drugs (DMARD) naïve RA patients (N = 11), methotrexate (MTX) treated RA patients (N = 18), and healthy controls (N = 9) matched for age, gender and smoking status.