Figure 4
(a) IL-10-mediated phosphorylation of signal transducer and activator of transcription (STAT) 1 and STAT3 in CD4+ T cells from patients with rheumatoid arthritis (RA) and from healthy controls (HC). CD4+ T cells (5 × 105 cells in 0.5 ml culture medium with 10% FCS) were incubated with or without IL-10 (1 and 10 ng/ml) and cells were harvested 20 min later. Whole cell extracts were prepared by placing cells in SDS buffer, and tyrosine phosophorylation (p-Tyr) of STAT1 and STAT3 was detected by western blot analysis. IFN-γ-stimulated Hela cells were used as a positive control for STAT1 phosphorylation. (b) Percentage of IL-10-activated STAT3 phosphorylation in CD4+ T cells from RA patients and from HC. Protein bands were quantified by densitometry using NIH-Image analysis, and STAT3 phosphorylation was expressed as % total STAT3 protein. (c) STAT3 phosphorylation in ST CD4+ T cells from RA patients. Representative results of STAT3 phosphorylation in CD4+ T cells from three synovial tissue samples of RA patients and three peripheral blood samples of HC are shown. Values are the mean ± standard error of the mean. n, number of samples tested.