Mice received irradiated B78-D14 cells with or without 10 μg of trAb Surek i.p. After 2 and 4 days, spleens were isolated and CD4+ T cells were phenotypically characterized. (A) Expression of CTLA-4 on CD4+ T cells. (B) Percentages of CD4+FoxP3+ cells. (C) Ki67 as a proliferation marker was stained in CD4+FoxP3+ T cells. (D) CTLA-4 upregulation is mainly restricted to the Treg population. Gating was done for CD4+ cells. At least 3 animals were included in each group. Columns indicate means and SEM. Statistics was done using the Mann-Whitney test.