CD4⁺ CD25⁺ regulatory cells restore oral tolerance in Ii^°/° mice. (A) Ii^°/° mice were left untreated (▴) or transferred intravenously with 1.10⁶ naive CD4⁺CD25⁺ T cells one day before gavage (ie, day –8) with either DNFB (•) or vehicle alone (○). (B) Ii^°/° mice were left untreated (▵) or transferred intravenously with either naive total CD4⁺ T cells (10 × 10⁶; □), CD4⁺CD25^– T cells (9 × 10⁶; ⋄), or CD4⁺CD25⁺ T cells (1 × 10⁶; ○) one day before gavage with DNFB. All mice were sensitized epicutaneously on day 0, and the CHS response was measured as described in Figure 1 legend. The data are expressed as mean values ± SD and are representative of at least 3 independent experiments.