Amount of H Antigen Expressed on Circulating von Willebrand Factor Is Modified by ABO Blood Group Genotype and Is a Major Determinant of Plasma von Willebrand Factor Antigen Levels

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Abstract
To investigate whether the effect of ABO blood group on plasma von Willebrand factor (vWF) levels is mediated by the ABH antigenic determinants carried on N -linked glycans of vWF, we studied 158 group A and group O healthy volunteers. vWF antigen (vWF:Ag) and factor VIII antigen (FVIII:Ag) levels were highest in A 1 A 1 individuals and higher in A 1 O 1 than in A 2 O 1 or O 1 O 1 individuals. Plasma A transferase activity and the amount of A antigen expressed per unit vWF ( AvWF ) were significantly higher in A 1 A 1 than in A 1 O 1 individuals and higher in A 1 O 1 than in A 2 O 1 individuals. AvWF was correlated strongly with plasma levels of A transferase activity. Thus, we have clearly demonstrated a direct relationship between ABO genotype, A transferase expression, and the amount of A antigen expressed on circulating vWF. H antigen expression per unit vWF ( HvWF ) was highest in group O individuals. Among group A individuals, the pattern of HvWF expression was A 2 O 1 > A 1 O 1 > A 1 A 1 . In group O and group A 2 O 1 individuals, HvWF was inversely correlated with plasma vWF levels. In contrast, among group A 1 A 1 and A 1 O 1 individuals, there was no relationship between AvWF and plasma vWF levels. These findings suggest that it is H antigen expression that mediates the ABO effect on plasma vWF concentration.