CD8⁺ T-cell response to PRAME in patients and donors. (A) Cumulative CD8⁺ T-cell response to stimulation with all 4 PRAME peptides, PRA100, PRA142, PRA300, and PRA425, in patients with myeloid leukemia (AML and CML), patients with ALL, and healthy donors. CD8⁺ T-cell responses to stimulation with the HLA-A*0201–restricted peptides: (B) PRA100, (C) PRA142, (D) PRA300, and (E) PRA425 in patients with leukemia (AML, ALL, and CML) compared with healthy donors. Values represent frequencies of PRAME-specific CD8⁺ T cells. (F) High- and low-avidity CD8⁺ T-cell responses determined by sensitivity to peptide concentration. Stimulation of PBMCs with 0.1 and 10 μM of PRA100, PRA142, PRA300, and PRA425 determined high- and low-avidity responses, respectively. Results shown are the ratios of high- to low-avidity CD8⁺ T-cell responses, calculated for patients with PRAME greater than 0.001 (○) and for patients with PRAME less than 0.001 (●). Ratios were obtained by the following calculation: IFN-γ plus CD8⁺ T cell (%) with 0.1 μM peptide/IFN-γ plus CD8⁺ T cell (%) with 10 μM peptide. Bars represent the median high/low-avidity ratio for each peptide.