CD79b-specific T-cell clones recognize malignant B-cell lines and primary B-cell malignancies. (A) T-cell clones K308 and S100 recognizing CD79b₁₇₃ and CD79b₂₀ peptides in the context of HLA-A2, respectively, were stimulated with 3 HLA-A2–positive ALL cell lines ALL-BV, ALL-CM, and ALL-RL at an S:R ratio of 10:1. Controls included CD79b-negative K562-A2 cells and CD79b-positive LCL-JY. (B) T-cell clone S100 was stimulated with 4 primary HLA-A2–positive primary CLL samples at an S:R ratio 10:1. (C-D) Clone K308 was tested against primary CLL (C) and primary ALL (D) samples at the indicated S:R ratios. The HLA-A2 genotype of primary samples is indicated in parentheses. Controls included samples that were exogenously loaded with 100 nM CD79b₁₇₃ peptide (3:1 + peptide). IFN-γ production was assessed using standard ELISA. (E-F) Cytotoxicity of K308 was determined for ALL cell lines and primary CLL and ALL samples. PKH26GL-labeled ALL cell lines (E) or primary CLL and ALL samples (F) were coincubated with K308 (K308) at different effector-to-target ratios for 17 hours. Living PKH26GL-labeled target cells were counted and analyzed by FACS, and the percent surviving cells was calculated (see Material and methods). Controls included a CMV-specific T-cell clone (CMV clone) recognizing irrelevant pp65-derived peptide NLVPMVATV presented in HLA-A2, and CD79b-negative K562-A2 cells. The experiment was carried out in triplicate showing mean ± standard deviation.