Y27 treatment effect on the percentage of CD4+CD25+FoxP3+ regulatory T (Treg) cells in peripheral blood, and the suppressive capacity of CD4+CD25+ Treg cells in BDF1 mice. Chronic graft-versus-host disease (GVHD) was induced in recipient BDF1 mice by two intravenous injections of donor parental DBA/2 mice lymphocytes. Y27 (10, 20 and 40 mg/kg) was given from 3 days after the last cell injection. The control and model mice received the same dose of vehicle (n = 7 per group). (A) and (B) Y27 treatment affect the percentage of peripheral blood CD4+CD25+FoxP3+ Treg cells. (C) Effect of Y27 treatment on the suppressive capacity of CD4+CD25+ Treg cells. Percent suppression = 100 × (cpm (CD4+CD25- Tconv) - cpm (CD4+CD25- Tconv + CD4+CD25+ Treg))/cpm (CD4+CD25- Tconv). Results represent mean ± standard error of the mean (SEM). **P < 0.01 versus control. Tconv, conventional CD4+CD25- effector T cells.