Definition of core peptide residues required for a response. (A) 5 × 10⁴ NG-1 cells were cultured with 1.0 × 10⁵ mitomycin C– treated autologous PBMC and indicated peptides at 5 μg/mL. Mean ± SEM of triplicate wells are shown. (K represents the amino acid generated by the fusion event). (B) 5 × 10⁴ NG-1 cells were incubated with 1 × 10⁵ autologous EBV-transformed B-lymphoblastoid cells (mitomycin C–treated) as APC and varying amounts of the truncated peptides as shown, or solvent as a negative control. Results are the mean ± SEM of triplicate wells.