Differential lysis of targets loaded with tumor or normal breast tissue–derived peptides by anti–BA46-induced CTL. CTL assays using anti–BA46-6, BA46-7, and BA46-9 or antitumor extract peptide-activated lymphocytes were performed as described in Methods, using RMA-S-HHD cells loaded with equal amounts (1 OD 230/5 × 105 cells/100 μl at the loading step) of tumor- and normal tissue–extracted peptides as targets. Specific lysis on tumor extract by CTLs induced by vaccination with different peptides was significantly higher than lysis of normal extract (P < 0.01). Results of a CTL assay using anti-Her2/Neu and tyrosinase-activated lymphocytes are presented as negative and positive controls, respectively. The E/T ratio of 50:1 is shown. Results represent the average of three similar experiments.