Effect of IL-10 on IFNγ-induced assembly of STAT1 dimers. (A) Monocytes were preincubated with 10 ng/mL of IL-10 for 90 minutes and then incubated with IFNγ for 20 minutes. Whole-cell extracts were prepared, and an EMSA was performed using the GRR probe, which is recognized by phosphorylated STAT1. The upper band of the shifted complex was presumed to be multimers of STAT1 binding to the probe. The autoradiograph represents that part of the total gel analyzed. (B) EMSA with GRR probe was performed as in (A), except that the indicated doses of IFNγ were used. The response was measured as a percentage of the maximum response of cells treated with IFNγ at 10 ng/mL. Three experiments were performed using individual donors, and the data are presented as the mean ± standard error. (○) Treated with IFNγ alone; (•) treated with IL-10 and IFNγ.