In addition, the frequencies of Treg cells within CD3+CD4+CD45RO− T cells (naive Treg cells) were also similar between RA patients and healthy controls (see Supplementary Figure 2B, available on the Arthritis & Rheumatology web site at http://onlinelibrary.wiley.com/doi/10.1002/art.39408/abstract). Here, CD4 is linked to rheumatoid arthritis.