Immunization of mice with 12B1-derived CRCL-loaded DCs induces BCR-ABL–specific CTL activity. Mice were immunized as described in “Materials and methods.” On day 0, splenocytes were harvested and cultured in the presence of 10 μg/mL 12B1 CRCL and 20 U/mL IL-2 for 6 days. Viable cells were then harvested by Ficol density centrifugation and used as effector cells. Day-5 bone marrow–derived DCs were incubated with 5 μg/mL HYLSTQSALSK or GFKQSSKAL peptide for 3 hours; alternatively, DCs were cocultured with 50 μg/mL 12B1 tumor-derived CRCL overnight. Cells were then collected and used as target cells. Effector cells were tested for cytolytic activity against indicated target cells by nonradioactive cytotoxicity assay kit (representative data from 2 experiments are shown). ▴ indicates PBS; □, DC; •, DC/12B1 CRCL; and ⋄, DC/BCR-ABL peptide.