Houle J J, Leddy J P, Rosenfeld S I
University of Rochester Medical Center, Department of Medicine, New York 14642.
Clin Immunol Immunopathol. 1989 Mar;50(3):385-93. doi: 10.1016/0090-1229(89)90145-1.
The terminal complement components, C8 and C9, and to a lesser extent C5, C6, and C7, but minimal amounts of C3, were shown to be associated with washed human platelets. In unactivated platelets, the complement components were detected in the platelet pellet by hemolytic assays after centrifugation and disruption of the platelets by freeze-thawing. However, after platelets had been activated by collagen, thrombin, or aggregated IgG to induce aggregation, the complement components were released into the supernatant. The rank order of hemolytic activity of C9, C8, C7, C6, and C5 detected in the supernatants of activated platelets was quite different from that found in serum from the same donors, in the same assays. In particular, the serum C7 hemolytic titer was more than twice the serum C9 hemolytic titer, whereas the activity of C9 detected from platelets was more than twice that of C7. This argues against a purely nonspecific uptake of these proteins by platelets from plasma. The functional role of terminal complement components released from platelets during activation is unknown, but it is tempting to speculate that these proteins may have a role in platelet-dependent immunological tissue injury. Because the C5b-9 membrane attack complex activates platelets, it is possible that release of terminal complement proteins serves to amplify platelet activation and may also play a role in diseases in which complement membrane attack complexes have been implicated.
终末补体成分C8和C9，以及程度较轻的C5、C6和C7，但仅有少量的C3，被证明与洗涤过的人血小板相关。在未激活的血小板中，通过溶血试验在离心以及冻融破坏血小板后，在血小板沉淀中检测到补体成分。然而，在血小板被胶原蛋白、凝血酶或聚集的免疫球蛋白激活以诱导聚集后，补体成分释放到上清液中。在激活血小板的上清液中检测到的C9、C8、C7、C6和C5的溶血活性顺序与在相同供体血清中在相同试验中发现的顺序有很大不同。特别是，血清C7溶血效价是血清C9溶血效价的两倍多，而从血小板中检测到的C9活性是C7的两倍多。这表明血小板并非单纯从血浆中非特异性摄取这些蛋白质。激活过程中从血小板释放的终末补体成分的功能作用尚不清楚，但很容易推测这些蛋白质可能在血小板依赖性免疫组织损伤中起作用。由于C5b - 9膜攻击复合物可激活血小板，终末补体蛋白的释放可能有助于放大血小板激活，并且可能在涉及补体膜攻击复合物的疾病中也起作用。
