T cells with increased appropriately matched TCR pairs at the cell surface recognize target cells more efficiently. (A) T cells mock transduced (×) or transduced with vα21_wt and vβ21_wt TCR chains (open symbols) or vα21_Cys and vβ21_Cys TCR chains (closed symbols) were selected by flow cytometry for lower (vβ21: MFI 7 ▴, ▵), intermediate (vβ21: MFI 12; •, ○), or higher (vβ21: MFI 50; ▪, □) levels of expression of the introduced vβ21 chain. The cell populations were analyzed with an IFNγ ELISPOT assay at the indicated peptide concentration at an effector-target (E/T) ratio of 0.3:1. (B-C) The proliferative responses of transduced T cells selected for expressing either vα21_wt vβ21_wt (vβ21_wt MFI 48; B, ▪; C, dotted line) or the vα21_Cys vβ21_Cys (vβ21_Cys MFI 45; B, □; C, dashed line) to stimulation with irrelevant (p53_264-272: p53) or relevant (WT1_126-134: WT1) peptide-pulsed irradiated PBMCs at a responder-stimulator (R/S) ratio of 1:1 assessed by (B) ³H-thymidine incorporation (C) or CFSE staining at 4 days. Statistical analysis in panel B was performed with a t test. Error bars indicate SEM. (D) Transduced T cells selected for expression of either vβ21_wt or the vβ21_Cys at an MFI of 7 were analyzed for recognition of 2 different AML samples (▴, ▵ and ▾, ▿) in a 5-hour ⁵¹chromium-release assay. The assays were performed in the presence of excess (20:1) cold target T2 cells pulsed with either the relevant (open symbols, thin lines) or irrelevant peptide (closed symbols, bold lines).