P435/NLT–specific CTLs can be generated from HLA-A*02⁺ patients. (A) Frequency of IFNγ⁺ CTLs specific for irrelevant (white bars), PRAME PepMix (black bars), P435 (gray bars) and P4 (striped bars) against specific peptides in 11 HLA-A*02⁺ patients with AML, CML, HL, or follicular lymphoma. NT indicates not tested. (B) PRAME-CTLs produced IFNγ⁺ SFCs in response to autologous CML blasts but not against HLA-A*02⁻ CML blasts, and this effect was HLA restricted because IFNγ⁺ SFCs were reduced when samples were preincubated with an anti–HLA class I antibody, but not with an isotype control. (C) Staining with the P435/NLT–specific tetramer of CTL lines generated from 3 representative patients.