aPL antibodies and a murine monoclonal anti-β₂GPI antibody (E7) increase thrombus size in a murine thrombosis model through an interaction with ApoER2. ApoER2^+/+ (filled bars) or ApoER2^−/− (open bars) mice were injected with either IgG-NHS, IgG-APS, MuMoAbC, or E7, as indicated in the section “Analysis of thrombus dynamics.” Thrombi were induced in the animals by the use of a standardized injury, and thrombus size was measured in square microns (μm²). The data are expressed as means ± SD (5-10 animals were used per group). The Mann-Whitney 2-tailed test was used to assess statistical significance. ¶Statistically different from apoER2^+/+ treated with control (P < .0001). *Statistically different from apoER2^+/+ treated with IgG-APS or E7(P < .0001). **Statistically different from apoER2^−/− treated with IgG-APS or E7(P < .0001).