FIGURE 7.

Binding of ¹²⁵I-labeled natalizumab Fab to T lymphoblastoid cells. A, time course of binding. B, saturation binding. C, inhibition of binding by unlabeled natalizumab Fab and IgG. D and E, binding of ¹²⁵I-Fab at different concentrations of input Fab and VCAM D1D2 fragment fit to an allosteric ternary complex model (D) or the Gaddum-Schild equation (E). Bars show S.E. for each data point in two or three triplicate experiments. F, different plot of same data as in D and E. Lines in B-D show fit to equations. Fit values are shown together with S.E. unless 95% confidence intervals (CI) are otherwise shown. α₄β₁ integrins on Jurkat T lymphoblastoid cells were activated with Mn²⁺ for 30 min at 37 °C, and equilibrium ¹²⁵I-Fab binding was measured after 2 h on ice as described under ”Experimental Procedures.“