Intracellular detection of IFN-γ and IL-4 by FACS analysis. (a) A representative of seven rheumatoid arthritis (RA) patients of which mean values are shown in (b). Cytokine production of the CD3/CD28 costimulated CD4+ T cells was assessed after 10 days of culture in the absence or presence of IL-7, of IL-4 or of their combination. Cytokine production of differentiated cells was analyzed upon ionomycin/phorbol myristate acetate stimulation for 6 hours in the presence of Brefeldin A. Means ± standard errors of the mean of percentages from cells of RA patients that produce IFN-γ but no IL-4 (Th1) and that produce IL-4 but no IFN-γ (Th2) upon differentiation are shown. *P < 0.05, **P < 0.01, statistically significant differences between control (con) culture and cultures with IL-7, with IL-4 or with IL-7 and IL-4. Significant differences between the cytokine treatments are indicated separately. PE, phycoerythrin; FITC, fluorescein isothiocyanate.