Steroid treatment selectively increased CD8⁺ Tregs in both the passive and active models of ITP. (A) In the passive model of ITP, mice were injected with anti-β3 mAb (9D2, 1 μg, intraperitoneally) at day 0. In some mice, 10 mg/kg DEX was administered via intraperitoneal injection 4 hours after antibody injection. On indicated days, mice were bled, and different CD8⁺ subsets were detected via flow cytometry. N = 8 to 10. (B) In the active model, mice were transfused with immunized β3^−/− splenocytes on day 0. DEX treatment (oral, 10 mg/kg) or control water was initiated on day 6. Mice were bled on the indicated days, and CD8⁺ subsets were detected as above. N = 6, *P < .05, **P < .01, ***P < .001. Mean ± SD.