CD79b expression and shRNA knockdown confirm CD79b specificity of isolated T-cell clones. (A) CD79b-negative K562 cells expressing either HLA-A2 (K562-A2) or HLA-B7 (K562-B7) were retrovirally transduced with codon-optimized CD79b (K562-A2 + CD79b or K562-B7 + CD79b) and sorted to high purity. CD79b-reactive T-cell clones K308 (CD79b₁₇₃:A2), S100 (CD79b₂₀:A2), and A23 (CD79b_9-17:B7) were coincubated with transductants. Control T-cell clone HSS12 recognizes a peptide of the ubiquitously expressed gene USP11 in the context of HLA-A2. (B) CD40L-activated CD19⁺ B cells of 2 HLA-A2–positive healthy individuals (SRA CD19⁺ and UHK CD19⁺) were transduced with CD79b-specific shRNA (shRNA) and selected by puromycin treatment or were left untreated (nt) and coincubated with T-cell clones K308 or S100 or control clone HSS12. Clones K308 and S100 were cocultured at a S:R ratio of 2:1. Control clone HSS was cocultured at an S:R ration of 10:1. IFN-γ production was determined using standard ELISA. Antigen-presenting capacity of transduced and nontransduced target cells was controlled by clone HSS12.