CD8⁺ T-cell response to stimulation with the HLAA*0201–restricted peptides CMV pp65, PR1, WT1, and BCR-ABL in 18 healthy donors and 14 patients with CML. (A) CMV pp65. (B) PR1. (C) WT1. (D) BCR-ABL. CD8⁺-selected T cells were incubated for 3 hours either with unpulsed APC or with APC pulsed with 3 doses of peptide (0.1, 1, and 10 μM). Values represent copies of IFN-γ mRNA per 10⁴ copies of CD8 mRNA. Because of limitation in the amount of PBMCs available, the intermediate dose testing was omitted in certain cases, and the data on intermediate and low avidity are presented together. The CD8⁺ T-cell response to stimulation with each particular peptide was calculated by subtraction of IFN-γ mRNA copies/10⁴ CD8 copies induced by unpulsed APC (background) from that induced by peptide-pulsed APC. Values more than 100 IFN-γ mRNA copies per 10⁴ copies of CD8 and at least 2 times that of background were defined as positive responses. Bars represent the median number of IFN-γ mRNA copies/10⁴ CD8 copies for each condition. Responses to stimulation with PR1 and WT1 were signifi-cantly higher in the CML group. Responses to stimulation with BCR-ABL were detectable only in the CML group.