CD4⁺CD25^hi Tregs from active RA patients are defective suppressors. (A) CD4⁺CD25^- responders (5 × 10⁴/well) and CD4⁺CD25^hi Tregs (5 × 10⁴/well) were cultured with plate-bound anti-CD3 (1 μg/well) either alone or at a 1:1 ratio. After 72 hours, ³H-thymidine incorporation was determined. CD4⁺CD25^- effectors from active RA patients were also cocultured with CD4⁺CD25^hi Tregs from healthy individuals. Results are the mean ± SEM of 3 separate experiments. (B) Culture supernatants were diluted and analyzed to determine the amount of interferon γ. Data represent the mean ± SE of 5 different experiments.