Cytolysis of antigen-specific T cells by K^b-CD28-ζ and K^b-CD28[L→G]- ζ RMTCs. (A) RMTCs were pulsed with 50 μg/mL ovalbumin 257-264 peptide or saline diluent, washed, and cultured for 6 hours with OT-1 TCR transgenic T lymphocytes at the designated effector-target ratio. Target cell survival was determined using quantitative flow cytometry. Specific cytolysis was calculated from the number of residual viable target cells in wells containing target cells pulsed with peptide compared with that in otherwise identical control wells including unpulsed effectors. (B) Similar to panel A, except experimental RMTCs were pulsed with the designated concentration of ovalbumin peptide. All samples were cultured at an effector-target ratio of 1. Data points are means of quintuplicate samples. Error bars show ± 1 SD. Plots are representative of 3 independent experiments.