Indications for a protective function of beta2-glycoprotein I in thrombotic thrombocytopenic purpura.

It has been shown that β(2) -glycoprotein I (β(2) GPI) interacts with von Willebrand factor (VWF) in a glycoprotein (GP)Ib binding state. Given the presence of active VWF multimers in thrombotic thrombocytopenic purpura (TTP), we speculated that β(2) GPI might play a role in TTP. We found that β(2) GPI plasma levels were significantly lower in acute and remission TTP patients than in normal controls, showing a direct correlation with ADAMTS 13 levels and an inverse correlation with the extent of VWF activation.

Proteomic screen identifies IGFBP7 as a novel component of endothelial cell-specific Weibel-Palade bodies.

Vascular endothelial cells contain unique storage organelles, designated Weibel-Palade bodies (WPBs), that deliver inflammatory and hemostatic mediators to the vascular lumen in response to agonists like thrombin and vasopressin. The main component of WPBs is von Willebrand factor (VWF), a multimeric glycoprotein crucial for platelet plug formation. In addition to VWF, several other components are known to be stored in WPBs, like osteoprotegerin, monocyte chemoattractant protein-1 and angiopoetin-2 (Ang-2).

Platelet-mediated proteolytic down regulation of the anticoagulant activity of protein S in individuals with haematological malignancies.

The natural anticoagulant protein S contains a so-called thrombin- sensitive region (TSR), which is susceptible to proteolytic cleavage. We have previously shown that a platelet-associated protease is able to cleave protein S under physiological plasma conditions in vitro . The aim of the present study was to investigate the relation between platelet-associated protein S cleaving activity and in vivo protein S cleavage, and to evaluate the impact of in vivo protein S cleavage on its anticoagulant activity.