Effect of aPL Abs on thrombus formation in A2^−/− mice. A2^−/− or A2^+/+ mice were treated with either IgG-APS, IgG-NHS (A), 4C5, anti-A2 MoAb, or MuMoAbC as control (B), as indicated in “Analysis of thrombus dynamics.” Thrombi were induced in the animals, and thrombus size was measured in square microns (μm²). The data are expressed as means ± SD (5-10 animals were used per group). ¶Statistically different from A2^+/+ mice treated with IgG-NHS (A; P = .001) or MuMoAbC (B; P = .002). *Statistically different from A2^+/+ mice treated with IgG-APS (A; P = .002) or 4C5 (B; P = .005). **Statistically different from A2^−/− mice treated with IgG-APS (A; P = .001) or 4C5 (B; P = .009).