Figure 2.

High-affinity CD8 variants enhance the sensitivity of antigen recognition via low-affinity TCRs.A–C, representative titration curves showing the activation of MEL5 TCR⁺ CD8αβ⁺ JRT3-T3.5 cells in response to C1R HLA-A2 cells pulsed with serial dilutions of the 3T (A), ELA (B), or FAT peptides (C) assessed by measuring the upregulation of CD69. MEL5 TCR⁺ CD8αβ⁺ JRT3-T3.5 cells were transduced with CD8αβ containing either wild-type (WT) CD8α (red) or mutated forms of CD8α, namely S53G (teal) or S53N (purple). D–F, functional sensitivity of MEL5 TCR⁺ CD8αβ⁺ JRT3-T3.5 cells expressed as the decimal cologarithm of the half-maximal efficacy concentration (pEC₅₀) for each of the conditions shown in A–C. Significance was determined using a one-way ANOVA with Dunnett’s post hoc test to compare each variant versus wild-type CD8 (n = 5). Data are derived from five separate experiments. G, data summary shown as baseline-corrected pEC₅₀ values relative to wild-type CD8. MFI, geometric mean fluorescence intensity.