MTS mice have normal percentages of peripheral CD4⁺ T_regs, which are able to efficiently suppress WT effector T-cell proliferation. (A) Spleen and LNs from WT and MTS mice were stained for the presence of intracellular FoxP3. Populations are gated on CD4⁺ T cells. Data are representative of 3 independent experiments of 2 or 3 mice per group. (B) Sorted CD4⁺CD25⁺ WT (black line) or MTS (gray lines) T cells were cultured in the presence of stimulated CD4⁺CD25⁻ WT effector cells, and proliferation was measured by tritiated thymidine incorporation. Data are mean ± SEM and are representative of 3 independent experiments.