Splenic T cells (purified using nylon wool columns) isolated from naive or grafted C57BL/6 mice serving as responders (2610 6 / well) were incubated for 7 days in the presence of Mitomycin Ctreated (50 mg/ml, Sigma-Aldrich) DCs used as stimulators derived from naive BALB/c mice (4610 5 /well, DC: T ratio of 1:5) in 12-well flat bottom plates (Nunc, Roskilde, Denmark). Cultures were kept at 37uC in 5% CO 2 atmosphere. Supernatants were recovered after 7 days for determination of IL-10 production. Cytokine level was quantified using Mouse IL-10 ELISA MAX TM Deluxe. T-cell proliferation was assessed by serial dilution of the intracellular CFSE dye as described previously [53] .