We thus compared the levels of IFN-γ production by CD4+ T cells after CD3 and CD28 costimulation in the presence of 1 ng/ml IL-10 in RA patients with active disease (multiple inflammatory joints, CRP level ≥ 10 mg/l) and inactive disease (in remission, CRP level < 10 mg/l) [26] and in healthy controls. There were no statistically significant differences in IFN-γ production without IL-10 among these three groups (Fig. 2a), but the inhibitory effect of IL-10 on IFN-γ production was significantly limited in the active RA group as compared with the inactive RA group and healthy controls (percentage decrease: active RA, 2.9 ± 14.4%; inactive RA, 45.6 ± 14.4%; controls, 65.8 ± 7.9%) (Fig. 2b). As a consequence, CD4+ T cells from active RA patients produced higher levels of IFN-γ in the presence of 1 ng/ml IL-10 than did normal CD4+ T cells (Fig. 2a).