ICOS and rheumatoid arthritis: Moreover, several of the genes observed as differentially methylated in our study have previously been found differentially methylated in inflammatory disorders and autoimmune diseases characterized by an interferon DNA methylation signature including systemic lupus erythematosus (LTA, RUNX3, NFATC2, PRKCZ) [46–48], Behçet’s disease (STAT4, RUNX3, PRKCZ) [49], multiple sclerosis (RUNX3, HLA-DOA, PRKCZ) [50, 51], primary Sjøgren’s syndrome (LTA, RUNX3, NFATC2, HLA-DOA, NFKB1, PRKCZ) [52–54] and rheumatoid arthritis (NFATC2, ICOS, NFKB1, PRKCZ) [55–57].