Generation and characterization of DKK1 peptide-specific CTL clones. Selection of T-cell clones specific for (A) P20 or (B) P66v, by measuring peptide-induced IFN-γ secretion by T-cell clones using ELISA assay. Cytotoxicity of a P20-specific T-cell clone (T16) and P66v-specific T-cell clone (T6) against (C) T2 cells pulsed with different concentrations of the immunizing peptides, or (D) T2 cells pulsed with the immunizing (Imm Pep; for P20-specific CTLs: P20; for P66v-specific CTLs: P66v), irrelevant (Irre Pep; for P20-specific CTLs: P66v; for P66v-specific CTLs: P20), or control peptides. Unpulsed T2 cells (T2) were used as negative control. An effector/target (E:T) ratio of 10:1 was used in panels C and D. Results of 4 independent experiments are shown. Error bars show SD. Similar results were obtained with other T-cell clones from blood donors and patients with myeloma.