FIGURE 6.

Formation and dissociation of the C3 convertase. A, C3b-coated SPR chip was exposed to IgG from healthy donors or LN patients. Subsequently, C3 convertase was formed by injection of FB and FD in Mg²⁺-containing buffer. Left, raw data with the step of the interaction of IgG with the immobilized C3b, followed by the introduction of FB and FD. Right, phase of interaction of FB + FD, where the curves are aligned at the moment of injection. B, formation of the C3 convertase and dissociation by FH in the presence of IgG from a healthy donor, measured by SPR. The spontaneous dissociation is shown in black, and the FH-mediated dissociation is shown in green. C, formation and FH-mediated dissociation of the C3 convertase in the presence of IgG from healthy donor (green) and IgG from two patients (JTH (red) and MMJ (blue)), measured by SPR. D, formation and FH-mediated dissociation of the C3 convertase in the presence of IgG from healthy donor and a IgG from patient. C3, FB, FD, and IgG were incubated in the absence or in the presence of FH for the indicated time. The reaction was stopped by the addition of a reducing sample buffer, and the cleavage pattern of C3 (the appearance of the α′ band, indicating the activity of the convertase and the generation of C3b) was evaluated by Western blot. The results for patient MMJ are shown.