Design of conditioning with 5-FU and KL. Recipient mice were prepared by administration of KL (50 μg/kg/injection at −21, −9, and +3 hours relative to 5-FU (125 mg/kg)) in 2 consecutive weeks. Ten million donor BM cells were injected into the tail vein at 24, 48, and 72 hours after the last 5-FU injection. See Materials and Methods for more detailed explanation.