TABLE 3.

Thermodynamic properties of hPD-1 binding to hPD-L1 and hPD-L2

Interactions of PD-1 with PD-L1 or PD-L2 were characterized at a range of temperatures from 10 to 25 °C by quantitative ITC analysis.

	Binding parameters
	na	K	Kda	ΔHa	−T·ΔSb	ΔG
		105m−1	μm	kcal mol−1	kcal mol−1	kcal mol−1
hPD-1 binding to hPD-L1
pH 6.0	0.904 ± 0.0098	6.28 ± 0.47	1.6	−2.23 ± 0.033	−5.66	−7.9
pH 7.4	0.865 ± 0.015	4.58 ± 0.49	2.2	−2.88 ± 0.068	−4.83	−7.7
pH 8.0	0.906 ± 0.018	3.29 ± 0.34	3.04	−2.69 ± 0.077	−4.83	−7.5
10 °C	1.23 ± 0.032	2.96 ± 0.65	3.38	0.87 ± 0.037	−7.95	−7.5
15 °C	0.602 ± 0.014	5.76 ± 1.80	1.74	−0.81 ± 0.078	−6.8	−7.8
20 °C	0.882 ± 0.014	5.11 ±0.48	1.96	−1.56 ± 0.035	−6.09	−7.8
25 °C	0.878 ± 0.057	5.41 ± 0.21	1.85	−2.77 ± 0.026	−5.07	−7.8
50 mm NaCl	0.842 ± 0.0073	6.15- ± 0.34	1.63	−3.24 ± 0.038	−4.65	−7.9
500 mm NaCl	0.902 ± 0.017	5.15 ± 0.61	1.94	−2.21 ± 0.058	−5.57	−7.8
hPD-1 binding to hPD-L2
pH 6.0	1.08 ± 0.0055	20.2 ± 0.97	0.5	−6.18 ± 0.043	−2.42	−8.6
pH 7.4	1.11 ± 0.0075	22.2 ± 1.50	0.45	−6.50 ± 0.059	−2.15	−8.66
pH 8.0	1.04 ± 0.006	17.8 ± 0.90	0.56	−7.24 ± 0.057	−1.29	−8.53
10 °C	0.982 ± 0.012	23.7 ± 2.60	0.42	−4.57 ± 0.081	−3.71	−8.5
15 °C	0.988 ± 0.015	37.7 ± 6.80	0.27	−4.96 ± 0.10	−3.72	−8.8
20 °C	1.09 ± 0.018	29.5 ± 5.50	0.34	−5.84 ± 0.14	−2.84	−8.7
25 °C	0.979 ± 0.0063	26.3 ± 1.70	0.38	−7.70 ± 0.067	−1.06	−8.8
50 mm NaCl	1.01 ± 0.0056	20.8 ± 1.10	0.48	−7.57 ± 0.057	−1.05	−8.6
500 mm NaCl	0.985 ± 0.0068	21.7 ± 1.40	0.46	−7.35 ± 0.068	−1.29	−8.6

^a The values for K_d, stoichiometry, and ΔH, obtained by fitting a single binding site model to the ITC data, are shown with S.E. values.

^b The ΔS value was calculated using the equation, ΔG = −RT × ln(K_a) = ΔH_obs − TΔS.