Table 1.

Correlation between pMHC Potency and TCR-pMHC Binding Parameters

TCR/pMHC Bond Parametera	IFN-γ Release (EC50)b		Cytotoxicity (1/log(EC50))b
	R2	p Value	R2	p Value
KD	0.719	1.70E-05	0.882	1.70E-04
koff	0.776	3.04E-06	0.960	3.73E-06
t1/2	0.358	0.0111	0.652	0.0085
kon	0.320	0.0179	0.633	0.0103
1/kon	0.012	0.6735	0.709	0.0044
ΔG	0.624	0.0002	0.746	0.0027
ΔH	0.077	0.2812	0.006	0.8424
-TΔS	0.001	0.9064	0.044	0.5901
ΔC	0.221	0.0569	0.110	0.3826
ΔG‡diss	0.462	0.0027	0.603	0.0138
ΔH‡diss	0.060	0.3443	0.108	0.3884
-TΔS‡diss	0.036	0.4666	0.070	0.4921
ΔC‡diss	0.047	0.4055	0.058	0.5327
ΔG‡ass	0.202	0.0700	0.127	0.3469
ΔH‡ass	0.098	0.2219	0.030	0.6539
-TΔS‡ass	0.012	0.6793	0.082	0.4544
ΔC‡ass	0.075	0.2891	0.034	0.6360

^aMeasured EC₅₀ values are correlated to various TCR-pMHC bond parameters via data fitting in Matlab. Standard methods are used to calculate the R² statistic, which is the square of the correlation coefficient for these simple models, and p values are obtained with an F-test. Details can be found in the Supplemental Information. The quality of the fit for several bond parameters is shown in Figure 3.

^bWe use the reciprocal of EC₅₀ for the cytotoxicity assay because it is obtained from a dilution curve. We take the log to account for effects of nonlinear loading of peptide to APCs. The use of EC₅₀ in both assays is discussed in the Supplemental Information.