The proportions of CD4+CD25−Foxp3+ T cells [1.00 (0.58–1.62) % vs. 0.67 (0.55–1.07) %; P < 0.05] and CD4+CD25+Foxp3+ Treg cells [7.07 (5.92–8.18) % vs. 6.31 (5.47–7.34) %; P < 0.05] were both significantly higher in the total RA patients than in the HCs. Here, CD4 is linked to rheumatoid arthritis.