FIGURE 1.
Generation of a phage antibody that selectively binds to C3b, but not native C3. Binding of S77 IgG (A) or a polyclonal anti-C3 antibody (C3 pAb, B) to C3b or C3 protein. Binding is expressed as the ratio of optical densities of the reaction mixtures measured at 450 and 630 nm. C, Biacore analysis of binding affinity of S77 to C3b, iC3, iC3b, and C3c. S77 was captured on a CM5 sensor chip. Increasing concentrations of S77 (3.1, 6.25, 12.5, 25, 50, and 100 nm) were injected for 180 s. The KD is calculated from binding curves showing response at equilibrium plotted against the concentration. D, the plasma concentration of C3 protein recognized by S77 IgG is significantly lower than the plasma concentration of total C3 proteins. Data in A and B represent average ± S.D. of triplicate measurements.