Increased numbers of Foxp3+CD25lowCD4+ Treg cells were detected in peripheral blood of patients with autoimmune diseases such as systemic lupus erythematosus, multiple sclerosis, type 1 diabetes and rheumatoid arthritis (59–63), and it was suggested that this may reflect an attempt to regulate an overt autoimmune response of pathogenic T cells and might contribute to the perpetuation of chronic inflammation (61, 64). Here, FOXP3 is linked to rheumatoid arthritis.