CD4 and rheumatoid arthritis: Rheumatoid arthritis patients with reduced bone mass showed elevated frequencies of CD4+CD28− T-cells compared to patients with normal bone mass [2.2% (0–41.2) vs. 0.5% (0.1–8.6), p = 0.013, Figure 1A], whereas the prevalence of CD8+CD28− T-cells was not different between the groups [45.2% (3.4–89.3) vs. 37.4% (10–61), p = 0.197, Figure 1B].