Restoration of oral tolerance by CD4⁺ T cells is MHC class II–dependent but is not mediated by IL-10 secretion. (A) Naive CD4⁺ T cells (10 × 10⁶) were transferred intravenously into Ii^°/° or Aβ^°/° recipient mice on day –8. (B) CD4⁺ T cells (10 × 10⁶) purified from either naive wild-type C57BL/6 (▴) or IL-10–deficient (□) mice were adoptively transferred in Ii^°/° mice on day –8. Groups of mice without cell transfer (▵) were used as control. All mice were then fed DNFB on day –7, sensitized on day 0 with DNFB, and ear challenged on day +5. Ear swelling was determined at 48 hours (A) or at various times after challenge (B). Results are expressed as mean values ± SD and are representative of 3 independent experiments.