Platelets, Endothelial Cells and von Willebrand Factor

In plasma and platelets (PI) from 10 patients (pts) with “severe” recessive von Willebrand’s disease (vWD) factor VIII-related antigen (VIIIR:AG) was unmeasurable in 7 and extremely low in 3 using a very sensitive immunoradiometric assay (IRMA); ristocetin cofactor (VIIIR:RCo) was always unmeasurable and VIM:AG was not detectable on immunofluorescence on endothelial cells (EC) of the vessel wall. In 12 pts with “classical”, dominant vWD characterized by reduced plasma level of VIIIR:AG and VI I IR:RCo, normal values were found in PI and the mobility of PI VIIIR:AG on crossed Immunoelectrophoresis was not different from that of normal controls; VIIIRr AG was normal on EC. In 7 pts showing a faster electrophoretic mobility of plasma VIIIR:AG (variant: vWD), the same abnormality was found in PI. VIIIR:AG concentration was normal both in plasma and in PI when measured by electroimmunodiffusion, whereas IRMA gave lower values and VI I IR:RCo was decreased; VIIIR:AG was normal on EC. These findings show that “severe” vWD is the expression of a marked reduction of factor VIII synthesis fully expressed in EC, PI and plasma. In “classical” vWD the plasma defects are not reflected in the cellular compartments, suggesting a defective transfer from EC and PI to plasma. Patients with “variant” vWD are the expression of a qualitative alteration of the factor VIII molecule, functionally defective both in PI and in plasma.

 

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