CTL clone RDR173 recognizes the minimal epitope RPHAIRRPLAL. (A) Overlapping 9-, 10-, and 11-mer peptides (1 μg/mL) were pulsed on donor-derived EBV-LCL cells for 2 hours at 37°C. Peptide-pulsed EBV-LCLs were cocultured with CTL clone RDR173 for 24 hours. Release of IFN-γ in the supernatant was measured by ELISA (shown as mean value ± SD). (B) Increasing concentrations of the patient-derived peptide RPHAIRRPLAL (•) and the donor-derived peptide RPRAIRRPLAL (○) were pulsed on donor-derived EBV-LCL cells for 2 hours at 37°C. Peptide-pulsed EBV-LCLs were cocultured with CTL clone RDR173 for 24 hours. Release of IFN-γ in the supernatant was measured by ELISA.