The production of IFN-γ and IL-4 by CD3/CD28 costimulated naive CD4+ T cells from healthy controls (n = 9, white bars) and rheumatoid arthritis (RA) patients (n = 9, black bars) differentiated during 10 days of culture in the presence of IL-7, of IL-4 or of IL-7 and IL-4. Cytokine production of differentiated cells was analyzed upon ionomycin/phorbol myristate acetate restimulation for 24 hours. Values are expressed as percentages of cytokine levels produced in the absence of exogenously added cytokines (control values set at 100% for RA patients and controls, respectively, were 47.1 ± 12 ng/ml versus 37.1 ± 5.7 ng/ml for IFN-γ, and 0.89 ± 0.21 ng/ml versus 0.95 ± 0.15 ng/ml for IL-4; not significantly different). #P < 0.05, statistically significant differences between RA patients and healthy controls; *P < 0.05, **P < 0.01, statistically significant differences between control and cytokine-treated cultures.