Immunization with Ba-P210–ICSBP cells activates CD8⁺ CTLs, which exhibit specific cytolytic activity against BCR/ABL-associated cell surface antigens.

(A) Cytolytic activity of Ba-P210–ICSBP immunized spleen cells against different cell targets. Five thousand ⁵¹Cr-labeled target cells were used: ⋄, Ba-P210; ■, Ba-P210–ICSBP; ♦, 3T3-MSV; ▪, LL2. (B) Cytotoxicity competition assay; 5000 ⁵¹Cr labeled Ba-P210 cells were used as target cells, and 125 000 Ba-P210–ICSBP immunized spleen cells were used as effector-cells (effector-target ratio of 25:1). An excess of unlabeled BaF3 or Ba-P210 cells were added to the target-effector mixture (40-fold or 90-fold as indicated). CTL activity was measured as described in “Materials and methods.” Graph represents the percentage of inhibition of cytolytic activity in the presence of unlabeled cells normalized against total cytolytic activity in the absence of unlabeled cells. (C) Cytolytic activities of CD8⁺/CD4⁺ cells or the corresponding CD8/CD4-depleted Ba-P210–ICSBP immunized spleen cells. Five thousand Ba-P210 cells were used as target and the effector-target cell ratio was 25:1.