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Figure S2. CD8 impact on TCR/pMHC monomer binding. (A–D) CD8 contribution to T1 TCR/pMHC monomer binding at 37°C using H-2K^d and H-2K^d_Δ223/227 (CD8 binding–deficient) monomers. 4L-K^d (■) and 4L-K^d_Δ223/227 (□; A), 4P-K^d (▲) and 4P-K^d_Δ223/227 (△; B), 4V-K^d (▼) and 4V-K^d_Δ223/227 (▽; C), 4S-K^d (●) and 4S-K^d_Δ223/227 (○) monomers (D). CD8-mediated changes in TCR/pMHC affinities are indicated (ΔK_d). (E and F) Temperature dependence of pMHC binding. (E) 4P-K^d_Δ223/227 binding (△) and 4P-K^d binding (▲) measurements performed at 0°C (dashed lines) or 37°C (solid lines). In the absence of CD8 binding, the T1 TCR has a similar affinity for 4P-K^d_Δ223/227 (△) at 0 and 37°C. However, in the presence of CD8 binding, the apparent affinity of the T1 TCR for 4P-K^d (▲) is 27.8-fold lower at 37°C compared with 0°C. (F) Apparent affinities (1/K_d) of 4P-K^d (▴), 4A-K^d (), and 4N-K^d (▽) at 0, 24, and 37°C.