FVIII-IC binding to C1q and immobilized Fc-γ receptor is impaired by VWF. FVIII-IC were generated with rhFVIII (3 IU/mL or 2.1 × 10−9 mol/L) incubated first with VWF (0-20 IU/mL) and then with anti-FVIII antibodies (0.5 μg/mL or 3.3 × 10−9 mol/L). Binding to complement component C1q (left panels) and to CD32 (right panels) was assessed by ELISA. As a source of anti-FVIII Abs, either single anti-FVIII IgG Abs (Ab1 and Ab2), a combination (Ab1-7), or pooled serum from immunized F8−/− mice (Ab-poly) were used. Bar charts show the binding relative to FVIII-IC alone. The mean value ± standard deviation (SD) of 3 independent experiments done in duplicates is shown (individual data points are depicted). Statistical test was 1-way analysis of variance (ANOVA) followed by Tukey honestly significant difference (HSD) test with the Bonferroni correction. Statistical significance is displayed respectively for C1q and CD32 binding, showing the comparison with FVIII-IC alone; ∗P < .05.
