At day 5 or 7, cells were restimulated with immobilized anti-CD3 (2 μg/ml) and anti-CD28 (2 μg/ml) (4 hr with BrefeldinA [10 μg/ml] in the last 2 hr) or with PdBU and Ionomycin (5 hr with BrefeldinA [1 μg/ml]).