MHCI-restricted CD8⁺ T-cell clones exhibit explicit peptide length recognition footprints. Target cells (6 × 10⁴) expressing either HLA A*0201 or HLA B*3508 were pulsed in duplicate with mixtures from 8mer, 9mer, 10mer, 11mer, 12mer, or 13mer CPL scans (100 μM) at 37°C. After 2 hours, 3 × 10⁴ ILA1 (A), 1E6 (B), MEL5 (C), or SB27 (D) CD8⁺ T cells were added and incubated overnight. The supernatant was then harvested and assayed for MIP1β by ELISA. For ILA1 and MEL5 CD8⁺ T cells, red, yellow, green, dark blue, mid blue, and light blue depict > 50%, 40%-50%, 30%-40%, 20%-30%, 10%-20%, and 0%-10% MIP1β production (pg/mL) in response to 10⁻⁵ M index peptide, respectively. For 1E6 and SB27 CD8⁺ T cells, red, orange, yellow, green, dark blue, and light blue depict > 100%, 80%-100%, 60%-80%, 40%-60%, 20%-40% and 0%-20% MIP1β production (pg/mL) in response to 10⁻⁵ M index peptide, respectively. Each heat map is representative of a minimum of 3 different replicate experiments, each performed in duplicate.