CD4 and rheumatoid arthritis: The prevalence of circulating CD4+CD28−FoxP3+ T-cells was higher in RA patients compared to healthy individuals [0.7% of total CD4+ (range 0–19.2) vs. 0.2% (0–17); p = 0.029; Figures 1A,B], whereas the frequency of CD4+CD28+FoxP3+CD25+ Tregs was equal in both groups [5% of total CD4+ (3.2–7.3) vs. 4.9% (3.2–9.5); p = 0.988; Figure 1C].