In vitro cytotoxicity of CD8⁺ T cells, the frequency of peptide-specific CD8⁺ T cells in vivo, and B-cell receptor–ABL levels. In vitro cytotoxicity of infused CTLs was tested with peptide-loaded antigen-presenting cells (DCs or T2 cells) as targets. Panels A and D confirm antigen-specific cytotoxicity against a human leukocyte Ag-A3–restricted B-cell receptor–ABL-derived peptide (A) and an human leukocyte Ag-A2-binding WT1 peptide (D) in patients 11 and 14, respectively. (B,E) The corresponding frequency of human leukocyte Ag/peptide tetramer-positive CD8⁺ T cells after transplantation and CD8⁺ T-cell infusion in each case. (C,F) B-cell receptor–ABL mRNA became undetectable in both patients, and PCR negativity was maintained until the last follow-up.