Y27 treatment influence on the percentage of CD4+CD25+FoxP3+ regulatory T (Treg) cells in peripheral blood, and the suppressive capacity of CD4+CD25+ Treg cells in MRL/ lpr mice. MRL/lpr mice (10 weeks old) were treated with vehicle control (saline), cyclophosphamide (CYC; 15 mg/kg), or Y27 (10, 20 and 40 mg/kg) for 10 weeks (n = 7 to 10 per group). (A) and (B) The percentage of peripheral blood CD4+CD25+FoxP3+ Treg cells is unaltered in Y27-treated MRL/lpr mice. (C) Suppressive capacity of CD4+CD25+ Treg cells is significantly increased after Y27 treatment 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 MRL/lpr. Tconv, conventional CD4+CD25- effector T cells.