ABO blood group modulates VWF proteolysis by ADAMTS13. ABO blood group regulates the susceptibility of VWF to proteolysis by ADAMTS13, with group O VWF being cleaved significantly more rapidly compared with non-O VWF. Although the mechanism underlying the effect of ABO group on ADAMTS13 susceptibility has not been defined, 2 N-linked glycan sites are located in the A2 domain adjacent to the ADAMTS13 cleavage site (inset).