Identification of the MCEs of the p210b3a2 fusion region for newly identified HLA-restriction elements. A panel of short peptides corresponding to the p210b3a2 fusion region (A) were tested in CRAs with different effector target pairs. The bolded K corresponds to the new amino acid inserted at the BCR-ABL fusion point. KOSE or B cell lines, B1 or B9, were pulsed with varying concentrations of synthetic peptides, and used as targets for T1/B9 or T1/33 CTL at serial E/T ratios in CRAs. Data with 5-μM peptides are shown as mean values ± SE from at least three experiments (B). Striped bars indicate CTL clone T1/B9(DRB5*0101) vs target B9 (allogeneic HLA-DRB1*1101) pulsed with different peptides indicated on the Y-axis, open bars clone T1/33(HLA-B*3501) vs B1 (autologous HLA-B*3501) and gray bars T1/33(HLA-B*3501) vs KOSE (allogeneic HLA-B*3503) pulsed with indicated peptides. Peptide avidity profiles (C) of T1/B9(DRB5*0101) vs B9(HLA-DRB1*1101) + A17S (triangle), T1/33(HLA-B*3501) vs B1(HLA-B*3501) + R9P (diamond), and T1/33(HLA-B*3501) vs KOSE(HLA-B*3503) + R9P (square) were compared over a wide range of peptide concentrations