CD4 and rheumatoid arthritis: Further analysis showed that OX40 expression on CD4+CD28− T cells was significantly increased in PB samples from patients with RA compared with those from control subjects (10.14 ± 3.98% vs 7.83 ± 4.28%, 6.91 ± 3.13%, respectively; P = 0.006) (Fig. 2b).