The T-cell response toward Bcr-Abl⁺ leukemia cells is HLA dependent and detectable in a CML patient. CD8⁺ T cells from HD no. 3 were stimulated with autologous Bcr-Abl WT⁺ DCs, and the IFN-γ production by the activated T-cell populations (n = 96) was measured by ELISpot after the third stimulation. (A) Box plot of the IFN-γ spots in the presence of following DCs: Bcr-Abl WT⁺ DCs (▒) or mock-transfected DCs (░) treated either with mAb W6/32, IgG control antibody, or without antibody. (B) CD8⁺ T lymphocytes derived from the same HLA-A2⁺ healthy donor were stimulated 3 times with autologous Bcr-Abl WT⁺ DCs (▒) or Bcr-Abl KD⁺ DCs (░). IFN-γ release of the activated T-cell populations (n = 60) was measured in the presence of Bcr-Abl⁺ leukemia cell lines. The box plots show the number of IFN-γ–releasing T cells upon restimulation with the HLA-A2⁺, Bcr-Abl⁺ cell lines K562-A2 and BV-173, and the HLA-A2^−, Bcr-Abl⁺ cell line K562. (C) CD8⁺ T lymphocytes derived from an HLA-A2⁺ healthy donor (HD no. 3) were stimulated 3 times with the autologous Bcr-Abl WT⁺ DCs (▒) or Bcr-Abl KD⁺ DCs (░). The IFN-γ release by the activated T-cell populations (n = 96) was measured in the presence of HLA-A2–matched, allogeneic PBMCs derived from an HLA-A2⁺ CML patient in chronic phase (CML patient no. 1). (D) IFN-γ production by CD8⁺ T lymphocytes derived from a CML patient (CML patient no. 2) that had been stimulated 3 times with autologous DCs transfected with Bcr-Abl WT or Bcr-Abl KD. Incubation of these preactivated T-cell populations (n = 120) with Bcr-Abl WT–transfected DCs resulted in a higher amount of IFN-γ spots than the coculture with mock-transfected DCs (left). Incubation with Bcr-Abl KD⁺ DCs did not result in a specific IFN-γ production compared with the mock control (middle). The magnitudes of responses against Bcr-Abl WT⁺ DCs (▒) or Bcr-Abl KD⁺ DCs (░) were statistically evaluated in a box plot showing the median distribution of IFN-γ–producing T-cell populations (right, *P < .001; **P = ns; Mann-Whitney test, whiskers as in Figure 1). (E) Bar graph comparing IFN-γ spot indices between 3 healthy donors (HD no. 1, HD no. 2, HD no. 4) and CML patient no. 2. Error bars are SE.