Cytolytic capacity of Bcl-2–specific CTLs. bcl₂₀₈-reactive CTLs were isolated from PBLs from a breast cancer patient using HLA-A2/bcl₂₀₈-coated magnetic beads. (A) A small fraction of these cells was cloned by limiting dilution and expanded. Response of 2 such clones (top and bottom rows) as measured in a GrB ELISPOT against no peptide or the bcl₂₀₈ peptide. Each experiment was performed in duplicate with 10³ effector cells/well. (B) The isolated bulk culture was analyzed for specific lysis of T2 cells with (▪) or without (□) bcl₂₀₈ peptide. (C) Lysis by bcl₂₀₈-isolated T cells of the HLA-A2–positive breast cancer cell line MDA-MB-231 (•) and the HLA-A2–negative breast cancer cell line ZR75-1 (○). E/T indicates effector-target ratio.