Kirchhofer D, Riederer M A, Baumgartner H R
F. Hoffmann-La Roche Ltd, Pharma Division, Preclinical Research, Basel, Switzerland.
Blood. 1997 Feb 15;89(4):1270-8.
The adhesion of leukocytes to platelets deposited at the site of vascular injury may represent an important mechanism by which leukocytes contribute to hemostasis and thrombosis. In this study, we examined whether, in comparison with their distribution in circulating blood, certain leukocyte types are enriched at sites of platelet deposition. We used an experimental vascular injury model, in which human fibrillar collagen was exposed to anticoagulated human whole blood flowing through parallel-plate chambers (venous shear rate, 65/s). The platelet-adherent leukocytes were detached by EDTA treatment and analyzed by flow cytometry using cell-type-specific antibodies. The predominant leukocytes found in platelet thrombi were polymorphonuclear leukocytes, accounting for 76% of bound leukocytes (62% in circulating blood), whereas T and B lymphocytes did not significantly accumulate on thrombi, comprising a fraction of less than 5% (32% in circulating blood). Monocytes constituted 16% of platelet thrombus-bound leukocytes, which represents an almost fourfold enrichment as compared with their proportion in circulating blood. Almost identical results were obtained when we analyzed leukocytes adhering to platelet monolayers, which were formed by blocking glycoprotein IIb-IIIa, thus preventing platelet aggregation on top of the collagen-adherent platelets. Furthermore, leukocyte adhesion to platelet monolayers was completely inhibited by an anti-P-selectin antibody (50% inhibitory concentration, 0.3 microg/mL), whereas it reached a plateau at about 70% inhibition on platelet thrombi. This difference could be explained by a possible function of glycoprotein IIb-IIIa in leukocyte immobilization to thrombi or by the high local concentration of P-selectin in the growing thrombi. The results suggest that, because of their known abilities to promote coagulation and thrombolysis, the monocytes and polymorphonuclear leukocytes accumulating on forming platelet thrombi could play an important role in modulating thrombotic and hemostatic processes.
白细胞与沉积在血管损伤部位的血小板的黏附可能代表白细胞参与止血和血栓形成的一种重要机制。在本研究中，我们检测了与循环血液中的分布相比，某些白细胞类型是否在血小板沉积部位富集。我们使用了一种实验性血管损伤模型，将人纤维状胶原暴露于流经平行板腔室的抗凝人全血中（静脉剪切速率为65/s）。通过EDTA处理使黏附于血小板的白细胞脱离，并用细胞类型特异性抗体通过流式细胞术进行分析。在血小板血栓中发现的主要白细胞是多形核白细胞，占结合白细胞的76%（循环血液中为62%），而T和B淋巴细胞在血栓上没有明显积聚，占比不到5%（循环血液中为32%）。单核细胞占血小板血栓结合白细胞的16%，与它们在循环血液中的比例相比，这代表了近四倍的富集。当我们分析黏附于血小板单层上的白细胞时，得到了几乎相同的结果，血小板单层是通过阻断糖蛋白IIb-IIIa形成的，从而防止血小板在胶原黏附的血小板上聚集。此外，抗P-选择素抗体可完全抑制白细胞与血小板单层的黏附（50%抑制浓度为0.3μg/mL），而对血小板血栓的抑制作用在约70%时达到平台期。这种差异可以通过糖蛋白IIb-IIIa在白细胞固定于血栓中的可能作用或生长血栓中P-选择素的高局部浓度来解释。结果表明，由于单核细胞和多形核白细胞已知具有促进凝血和溶栓的能力，因此在形成的血小板血栓上积聚的这些细胞可能在调节血栓形成和止血过程中发挥重要作用。
