PRAME CTLs can target PRAME⁺ CML tumor cells. (A) Expression of PRAME mRNA in PBMCs isolated from 8 patients with CML and from a pool of 4 representative healthy donors. In 1 of the HLA-A*02⁺ CML patients, PRAME mRNA was undetectable (< 10⁻¹ normalized copies) as in healthy donors. (B) shows IFNγ production by PRAME CTLs (■) or by ELA-specific CTLs () generated from healthy donors against blasts obtained from CML patients. Significant numbers of IFNγ + SFC were detected in response to PRAME⁺/HLA-A*02⁺ CML cells (patients 3 and 4) but not in response to HLA-A*02⁺ CML cells with undetectable PRAME expression (patient 7) or PRAME⁺/HLA-A*02⁻ CML cells (patient 8). Negligible numbers of IFNγ⁺SFC were released by ELA-specific CTLs. (C) IFNγ production by PRAME CTLs in response to PRAME⁺/HLA-A*02⁺ CML cells is reduced by MHC class I antibody.