Figure 5
(a) Activation of signal transducer and activator of transcription (STAT) 3 in normal CD4+ T cells by serum IL-6 from patients with rheumatoid arthritis (RA). CD4+ T cells from healthy controls (5 × 105 cells in 0.5 ml culture medium) were stimulated by 30% RA serum in the presence of neutralizing anti-IL-6 antibody (Ab) (40 μg/ml) or of control antibody (40 μg/ml) for 20 min. Phosophorylation of STAT1 and STAT3 was detected by western blot analysis.(b) Effect of IL-6 pretreatment on IL-10 inhibition of IFN-γ production by CD4+ T cells. CD4+ T cells (5 × 105 cells in 0.5 ml culture medium with 10% FCS) were incubated with or without IL-6 (10 ng/ml) for 36 hours, and were then stimulated by anti-CD3 antibody and anti-CD28 antibody in the presence or absence of IL-10 (1 ng/ml) for 36 hours. Concentrations of IFN-γ in culture supernatants were measured in duplicate by ELISA. IFN-γ production with IL-10 was expressed as % IFN-γ production without IL-10. Values are the mean ± standard error of the mean. n, number of samples tested. P-Tyr, tyrosine phosophorylation.