Localization of the Th epitopes recognized by the CD4⁺ T-cell clones generated from the HB-1–specific bulk cultures. Production of IFN-γ by the CD4⁺ clones was tested on stimulation with autologous EBV-LCLs pulsed with the HB-1 protein or HB-1–derived peptides. Error bars represent 1 SD of triplicates.