C2 and hemophilia A: Structural analysis of C2 bound to BO2C11, a classical antibody inhibitor from a severe hemophilia A patient, supports the model of fVIII platelet association through residues M2199-F2200 and L2251-L2252 as they are completely sequestered in the BO2C11 paratope, potently blocking membrane binding (Figure 1C) (Jacquemin et al., 1998; Spiegel et al., 2001).