TF and serum lipopolysaccharide activity: Another source of tissue factor in vivo might be polymorphonuclear cells, whose inappropriate activation and positioning within the microvasculature strongly contributes to the pathological manifestations of multiple organ failure.77 Indeed, TF-positive neutrophils have been observed in the circulation of septic or endotoxemic animals.76,78 However, de Vaard et al.79 showed that TF-positive granulocytes infiltrating organs do not express TF mRNA in a mouse model of endotoxemia suggesting that they can acquire TF by binding monocyte-derived MPs.