FIGURE 1.

Inhibition of the classical complement pathway activation by hemin. The capacity of native and hemin-exposed C1q, bound to IgG-containing immune complexes or ligand-bound CRP to activate the classical complement pathway, was evaluated by ELISA. C1q (0.1 μm) was exposed to increasing concentrations of hemin (0–15 μm) and was allowed to interact with immune complexes (tetanus toxoid, anti-tetanus toxoid antibodies from an IVIg preparation) and PnC-bound CRP. C1q-depleted serum was added as a source of complement proteins. A, C1q binding; B, C3 deposition; C, MAC formation; D, sC5b-9 release in the fluid phase, measured by Quidel ELISA kit. The results for the native C1q were taken as 100%. Each point represents mean ± S.D. of three repetitions.