VWF and serum lipopolysaccharide activity: Ultra-large VWF multimers (UL-VWF) are stored in endothelial Weibel-Palade bodies or in alpha granules of platelets7 and can only be detected in the plasma after endothelial cell activation, i.e. in endotoxemia, thrombosis or thrombotic thrombocytopenic purpura (TTP)8.