Immunoelectron microscopic localization of factor VIII-related antigen in the vascular endothelial cells of a patient with type 1 von Willebrand disease.

The intracellular localization of a factor VIII-related antigen in human umbilical veins derived both from a patient with 'severe Type 1' von Willebrand disease and from a normal full-term baby was investigated by immunoelectron microscopy. In normal vascular endothelial cells, the factor VIII-related antigen was detected in Weibel-Palade bodies. The endothelial cells of von Willebrand disease did not include these structures, but were filled with distended vesicles, in which the factor VIII-related antigen was found immunohistochemically. These results suggest that Type 1 von Willebrand disease causes dysfunction of blood coagulation by suppressing secretion of factor VIII-related antigen into the blood.