Human naïve CD4+ T cells were stimulated with aCD3, aCD28, aSF3, and/or IgG Isotype control (ISO) for 18 h, after which CD25 expression was assessed by flow cytometry. (A) Gating strategy and representative dot plot showing CD25 frequency (%, top number) and MFI (bottom number). (B) Cumulative data showing CD25 MFI expression. Data are mean ± SEM; n = 18.