Control of the pathogenic effect of IgG aPL⁺ by MBB2ΔCH2. (A) Thrombus formation and (B) vessel occlusion observed in rats that received IgG (10 mg/mL) purified from 3 APS patients (P1, ▪ and □; P2, ▲ and △; P3, ● and ○) and either MBB2ΔCH2 (dashed lines, empty symbols) or control MB (2 mg/mL, continuous lines, filled symbols). The difference in thrombus formation and vessel occlusion between the rats treated with both IgG aPL⁺ and MBB2ΔCH2 reached statistical significance 15 minutes after infusion of the IgG from patient 2 and 30 minutes after the injection of the IgG from the other 2 patients. (C) Percentage of fetal loss in pregnant mice receiving patient IgG and MBB2ΔCH2. (D) Displacement of patient IgG bound to β2GPI by MBB2ΔCH2 evaluated as described in Methods. The procoagulant and proabortive effects of MBB2 and MBB2ΔCH2 were evaluated and analyzed as reported in Figure 2. The results of vascular occlusion are expressed as mean ± SD; percentages of fetal loss are expressed as median ± interquartile range presented as box plots. *P < .05.