Department of Medical Biology, Faculty of Health Sciences, University of Tromsø, Tromsø, Norway.
Thromb Res. 2010 Apr;125 Suppl 1:S31-4. doi: 10.1016/j.thromres.2010.01.032. Epub 2010 Feb 10.
The popular concept of TF serving predominantly as a hemostatic envelope encapsulating the vascular bed, has recently been challenged by the observation that blood of healthy individuals may form TF-induced thrombus under conditions entailing shear stress and activated platelets, corroborating the notion of blood borne TF. Accordingly, small amounts of TF activity is detected in calcium ionophore-stimulated monocytes, whereas it is questionable whether neutrophils and eosinophils express TF. Still there are contradicting reports on TF synthesis and expression in activated platelets, but when using a very sensitive and specific assay for TF activity measurements, we fail to detect TF activity associated with platelets activated with various agonists. However, activated platelets may play a role in decrypting monocyte TF activity in a process entailing transfer of TF to activated platelets in a P-selectin-PSGL-1 reaction whereby inactive TF (encrypted) becomes active through the availability of clusters of phosphatidylserine. Microparticles from plasma of healthy subjects possess weak TF-like activity which is not inactivated by anti-TF antibody. Endothelial cells are well documented to synthesize TF by several agonists in vitro. In contrast, there is little evidence that these cells are capable of synthesizing TF in vivo, and a recent report fails to show that TF on the endothelium may play any role in thrombin generation in a murine endotoxemia model. It may be concluded that monocytes are the only blood cells that synthesize and express TF and which may be the only source for TF-induced thrombosis when the endothelium is intact.
TF 主要作为一种止血包膜来包裹血管床的流行概念，最近受到了挑战，因为观察到健康个体的血液在涉及切应力和活化血小板的情况下可能会形成 TF 诱导的血栓，这印证了血液来源的 TF 的概念。因此，在钙离子载体刺激的单核细胞中可以检测到少量的 TF 活性，而中性粒细胞和嗜酸性粒细胞是否表达 TF 则存在疑问。关于活化血小板中 TF 的合成和表达仍存在相互矛盾的报道，但当使用非常敏感和特异的 TF 活性测定法时，我们未能检测到与各种激动剂激活的血小板相关的 TF 活性。然而，活化的血小板可能在解密单核细胞 TF 活性的过程中发挥作用，这一过程涉及 TF 通过 P-选择素-PSGL-1 反应转移至活化的血小板，在此过程中无活性的 TF（被加密）通过磷酯酰丝氨酸簇的可用性而变得具有活性。来自健康受试者血浆的微粒具有微弱的 TF 样活性，不能被抗 TF 抗体失活。体外实验已充分证明内皮细胞可被几种激动剂合成 TF。相比之下，几乎没有证据表明这些细胞在体内有能力合成 TF，最近的一份报告未能表明内皮细胞上的 TF 在小鼠内毒素血症模型中的凝血酶生成中可能发挥任何作用。可以得出结论，单核细胞是唯一合成和表达 TF 的血液细胞，并且在血管内皮完整的情况下，可能是 TF 诱导血栓形成的唯一来源。
