Ag sensitivity correlates with TCR avidity. Clones with different AgS levels were labeled with KK10/HLA-B*2705 tetramer across a range of concentrations. (A) Representative tetramer titrations for 1 clone with lower (H8B) and 1 clone with higher (C2A) levels of AgS. (B-C) Representative tetramer titration curves for several clones displayed as a percentage (B) or MFI (C) of tetramer⁺ cells. The symbol key shown in panel B applies to both panels. (D-E) Correlation between AgS (EC₅₀ for Cr⁵¹ release) and TCR avidity displayed as tetramer concentration EC₅₀ for percentage (D) or MFI (E) of tetramer⁺ cells. Data are shown for both standard (●) and CD8-null (○) tetramer titration assays. Correlations were determined using the Spearman rank test.