FIGURE 2.

Both CD25⁺ and PI-T_Reg cells maintain their suppressive phenotype following expansion in IL-2 in vitro. CD25⁺ and PI-T_Reg cells were cultured with IL-2 and Ac1-9 (10 μg/ml) for 5 days and CD4⁺ cells were purified using magnetic beads. Purified CD25⁺ (A) or PI-T_Reg cells (B) were cultured with freshly isolated naive CD4⁺ Tg4 T cells at the indicated ratios. CD4⁺ T cells were cultured at 5 × 10⁴ cells per well with 1 × 10⁵ cells per well of irradiated CD4-depleted splenocytes in vitro with 100 μg/ml Ac1-9. Tritiated thymidine was added after 72 h. Results are depicted as mean thymidine incorporation for duplicate cultures ± SEM. The experiment has been repeated three times with similar results.