FIGURE 3.

Strong activation of pStat1 counteracts pStat3-mediated inhibition of Treg function. CD4⁺CD25^– and CD4⁺CD25^high T cell populations 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 as in Fig. 2, and the blot shown is representative of two separate experiments. B and C, T cells were cocultured for 7 d in MLRs with allogeneic APCs. Indicated cytokines were added on day 0 (all at 50 ng/ml), and proliferation was assessed by [³H] incorporation. Data shown are the mean ± SEM of two separate experiments, and p values were adjusted using the Bonferroni method. D, Levels of pStat3, total Stat3, pStat1, and total Stat1 were calculated from immunoblots using densitometry (see Materials and Methods). The mean ratio of normalized pStat3/pStat1 following 30 min of cytokine stimulation is expressed ± SEM, and each bar represents the mean of at least three healthy human donors.