Analysis of clones derived from PRAME CTLs. (A) Specificity of representative single-cell clones targeting the ALY peptide, generated by limiting dilution assay. These representative CTL clones produced significant amounts of IFNγ in response to the ALY peptide but not to ELA-irrelevant peptide. (B) Functional specificity of 3 representative ALY-specific T-cell clones against PRAME⁺ tumor cell lines. These clones lysed HLA-A*02⁺/PRAME⁺ cell lines (BV173, ■ and U266-B1, ) but not the HLA-A*02⁻/PRAME⁺ cell line (L428, □). (C) Two representative ALY-specific T-cell clones produce significant amounts of IFNγ in response to blasts isolated from a HLA-A*02⁺/PRAME⁺ CML patient (patient 4) in a MHC class I–restricted fashion.