WT1-specific T cells induced by DNA vaccination are peptide specific and kill target cells presenting WT1. Splenocyte cultures from individual mice previously immunized with (A) p.DOM-WT1.37, (B) p.DOM-WT1.126, or (C) p.DOM-WT1.235 were established by stimulation in vitro for 2 weeks before assessing cytotoxicity by ⁵¹Cr-release assay. Cytotoxicity was assessed at the effector:target ratios shown, against human tumor cells endogenously expressing WT1 and stably transduced with the chimeric humanized MHC class I molecule, HHD, denoted as HHD⁺WT1⁺ (specifically, KYO-HHD (A and C) or 697-HHD (B) cells). Cell lines expressing either WT1 (HHD⁻WT1⁺) or HHD (HHD⁺WT1⁻) were included as negative controls (KYO-1 and C1RA2-HHD, respectively), HHD-transduced cells pulsed with the relevant peptide were used as positive controls.