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Deletion of Crry and DAF on murine platelets stimulates thrombopoiesis and increases factor H-dependent resistance of peripheral platelets to complement attack
发布于：2013年5月19日 文字：【大】【中】【小】
J Immunol. 2013 Mar 15;190(6):2886-95. doi: 10.4049/jimmunol.1202536. Epub 2013 Feb 6.
Deletion of Crry and DAF on murine platelets stimulates thrombopoiesis and increases factor H-dependent resistance of peripheral platelets to complement attack.
Barata L, Miwa T, Sato S, Kim D, Mohammed I, Song WC.
Source
Department of Pharmacology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19401, USA.
Abstract
Complement receptor 1-related gene/protein y (Crry) and decay-accelerating factor (DAF) are two murine membrane C3 complement regulators with overlapping functions. Crry deletion is embryonically lethal whereas DAF-deficient mice are generally healthy. Crry(-/-)DAF(-/-) mice were viable on a C3(-/-) background, but platelets from such mice were rapidly destroyed when transfused into C3-sufficient mice.In this study, we used the cre-lox system to delete platelet Crry in DAF(-/-) mice and studied Crry/DAF-deficient platelet development in vivo. Rather than displaying thrombocytopenia, Pf4-Cre(+)-Crry(flox/flox) mice had normal platelet counts and their peripheral platelets were resistant to complement attack. However, chimera mice generated with Pf4-Cre(+)-Crry(flox/flox) bone marrows showed platelets from C3(-/-) but not C3(+/+) recipients to be sensitive to complement activation, suggesting that circulating platelets in Pf4-Cre(+)-Crry(flox/flox) mice were naturally selected in a complement-sufficient environment. Notably, Pf4-Cre(+)-Crry(flox/flox) mouse platelets became complement susceptible when factor H function was blocked. Examination of Pf4-Cre(+)-Crry(flox/flox) mouse bone marrows revealed exceedingly active thrombopoiesis. Thus, under in vivo conditions, Crry/DAF deficiency on platelets led to abnormal platelet turnover, but peripheral platelet count was compensated for by increased thrombopoiesis. Selective survival of Crry/DAF-deficient platelets aided by factor H protection and compensatory thrombopoiesis demonstrates the cooperation between membrane and fluid phase complement inhibitors and the body's ability to adaptively respond to complement regulator deficiencies.
补体受体1相关基因/蛋白Y(Crry)和衰变加速因子(DAF)是两种鼠类细胞膜上的补体C3调节因子，二者具有相似的功能。Crry敲除对于胚胎是致命的，但是DAF缺陷的小鼠一般都可健康存活。Crry(-/-)DAF(-/-)小鼠在C3(-/-)的遗传背景上可以存活，但是将从这种小鼠体内提取的血小板转移至无C3缺陷的小鼠体内时，血小板会被迅速破坏。本研究中，我们采用cre-lox系统去除DAF(-/-)小鼠血小板上的Crry，在体外研究Crry/DAF缺陷的血小板的发育。Pf4-Cre(+)-Crry(flox/flox)小鼠体内血小板数目正常，并没有出现血小板减少症。其外周血血小板对补体攻击具有一定的抵抗力。但是，使用Pf4-Cre(+)-Crry(flox/flox)小鼠骨髓建立的嵌合体小鼠模型显示，C3(-/-)受体小鼠的血小板对补体活化敏感，而C3(+/+)受体小鼠的血小板对补体活化不敏感。这提示Pf4-Cre(+)-Crry(flox/flox)小鼠循环中的血小板发育过程中的自然选择是受补体影响的。值得注意的是，当H因子的功能被抑制时，Pf4-Cre(+)-Crry(flox/flox)小鼠的血小板对补体敏感。对Pf4-Cre(+)-Crry(flox/flox)小鼠骨髓检测发现血小板生成异常活跃。因此，在体外环境中，血小板Crry/DAF缺陷可以导致血小板功能异常，但外周血小板计数由于血小板生成活跃而不受影响。Crry/DAF缺陷血小板的自然选择可以受到H因子的保护和血小板生成的补偿作用，这证实了膜表面和循环中补体抑制因子的协同作用，以及机体对补体调节因子缺陷的适应性。