FIGURE 2.

Stat3 phosphorylation in response to IL-21, but not IL-27, also inhibits Treg function. CD4⁺CD25^– and CD4⁺CD25^high Tregs were isolated from peripheral blood of healthy donors. A, CD4⁺CD25^– T cells were stimulated for 30 min with 10 ng/ml of indicated cytokines. Protein lysates were prepared and probed with Abs specific for phosphorylated (p)-Y705 (activated) Stat3, p-Y701 (activated) Stat1, p-T202/p-Y204 (activated) Erk1/2, and total Stat3. The blot shown is representative of three separate experiments. B–D, Cells were cocultured for 7 d in MLRs with allogeneic APCs, and 50 ng/ml of indicated cytokines was added on day 0. Proliferation was assessed by [³H] incorporation for the final 16 h of culture. D, Where indicated, EGCG was added at 10 ng/ml on day 0 of coculture. Results shown are the mean ± SEM of two (D) or three (B, C) separate experiments, and p values were adjusted using the Bonferroni method.