PRAME-CTLs generated using PRAME-PepMix are polyclonal. We evaluated the polyclonality of the expanded lines by assessing their reactivity against an array consisting of 13 subpools of overlapping 15-mers spanning the entire PRAME protein. (A) Percentage of CTL lines (generated from 14 donors) responding to each of the 13 subpools. The majority of the CTL lines reacted against subpools 7 and 11. (B) Frequency of these CTLs responding to the PRAME-PepMix and each subpool as assessed by IFNγ ELISpot assay. Shown are the means ± SD of the responding lines. The highest reactivity of PRAME-PepMix CTLs was observed for subpool 11.