(A) Tregs from both AA patients and HDs were sensitive to IL-2 (at 0.5 and 1 U/mL concentrations) as evident by STAT5 phosphorylation after 15 and 30 minutes. Flow cytometry results are representative of 8 experiments (2 HDs and 6 AA patients). (B) Expanded Tregs were >90% FOXP3⁺ following expansion. (C) There was no significant difference between AA and HD Tregs in terms of fold-change increase after 4 weeks’ expansion (represents median-fold increase of 3 HDs and 3 AA). Error bars are standard error of mean. (D) Expanded Tregs were able to suppress T_con proliferation in both autologous and allogeneic settings (crisscross assay) (1:1 Treg/T_con ratio after 96 hours’ culture). It is noticeable that in this experiments, Tcon_AA were proliferating slightly more than T_conHD in the presence of expanded Tregs (6.43% vs 3.86%); however, this difference was not statistically significant when all replicates were compared. T_con was stained by violet proliferation dye (VPD). T_conAA, conventional T cells from AA patients; T_conHD, conventional T cells from healthy donors; Tr_eAA, expanded Tregs from AA patients; Tr_eHD, expanded Tregs from healthy donors.