The 1E6 TCR exhibits a strict preference for 10mer peptides. C1R-HLA A*0201 cells (6 × 10⁴) were pulsed with the indicated 9mer (A-B) or 10mer (C-D) peptides at the concentrations depicted for 2 hours at 37°C. Subsequently, 3 × 10⁴ 1E6 CD8⁺ T cells were added and incubated overnight. The supernatant was then harvested and assayed for MIP1β by ELISA. Error bars represent SDs.