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. 1997 Mar 4;94(5):1657–1662. doi: 10.1073/pnas.94.5.1657

Table 2.

Equilibrium binding of IL-4 variants to IL4-BP and to the receptor on T cells is similar but differs from their T cell proliferative activity

IL-4 variant Kd (IL4-BP), nM
Equilib. Kd (T cells), nM EC50 for T cell proliferation, nM
koff/kon Equilib.
IL4 0.16 0.11 0.12
I5A 1.2 1.1 0.83 0.08
T6A 0.14 0.06 0.11
Q8A 0.16 0.1
E9Q 31 24 16* 3.1
E9A ND
I11A 0.18
K12S 0.15
T13A 0.84 0.83 0.5 0.12
N15A 0.15 0.11
S16A 0.12 0.11
E19A 0.094 0.13
R53Q 0.66 0.72 0.68* 0.13
K77A 0.21
Q78A 0.2
R81A 0.36 0.08
F82A 0.14 0.1
K84A 0.29 0.1
R85A 0.33 0.09
R88Q 19 19 20* 2.5
R88A 92 110 140 8.1
N89A 2.3 1.5 2.3 0.09
W91A 0.55 0.56 0.25 0.09

The Kd values of IL-4 variants were calculated from the kinetic constants of Table 1 (Kd = koff/kon) and from equilibrium binding to biosensor-immobilized IL4-BP. The Kd values for IL-4 variants and the receptor on T cells were determined by competitive radioligand binding. The EC50 values are the concentrations effecting half-maximal proliferation of T cells. ND, not determined. 

*Data from ref. 11

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