Lappegård Knut Tore, Christiansen Dorte, Pharo Anne, Thorgersen Ebbe Billmann, Hellerud Bernt Christian, Lindstad Julie, Nielsen Erik Waage, Bergseth Grethe, Fadnes Dag, Abrahamsen Tore G, Høiby E Arne, Schejbel Lone, Garred Peter, Lambris John D, Harboe Morten, Mollnes Tom Eirik
Department of Medicine, Nordland Hospital, Bodø, and University of Tromsø, Norway.
Proc Natl Acad Sci U S A. 2009 Sep 15;106(37):15861-6. doi: 10.1073/pnas.0903613106. Epub 2009 Aug 26.
Complement component C5 is crucial for experimental animal inflammatory tissue damage; however, its involvement in human inflammation is incompletely understood. The responses to gram-negative bacteria were here studied taking advantage of human genetic complement-deficiencies--nature's own knockouts--including a previously undescribed C5 defect. Such deficiencies provide a unique tool for investigating the biological role of proteins. The experimental conditions allowed cross-talk between the different inflammatory pathways using a whole blood model based on the anticoagulant lepirudin, which does not interfere with the complement system. Expression of tissue factor, cell adhesion molecules, and oxidative burst depended highly on C5, mediated through the activation product C5a, whereas granulocyte enzyme release relied mainly on C3 and was C5a-independent. Release of cytokines and chemokines was mediated to varying degrees by complement and CD14; for example, interleukin (IL)-1beta and IL-8 were more dependent on complement than IFN-gamma and IL-6, which were highly dependent on CD14. IL-1 receptor antagonist (IL-1ra) and IFN-gamma inducible protein 10 (IP-10) were fully dependent on CD14 and inversely regulated by complement, that is, complement deficiency and complement inhibition enhanced their release. Granulocyte responses were mainly complement-dependent, whereas monocyte responses were more dependent on CD14. Notably, all responses were abolished by combined neutralization of complement and CD14. The present study provides important insight into the comprehensive role of complement in human inflammatory responses to gram-negative bacteria.
补体成分C5对实验动物的炎症组织损伤至关重要；然而，其在人类炎症中的作用尚未完全明确。本研究利用人类遗传性补体缺陷——即天然的基因敲除个体，包括一种此前未被描述的C5缺陷，来研究对革兰氏阴性菌的反应。这些缺陷为研究蛋白质的生物学作用提供了独特的工具。实验条件允许使用基于抗凝剂水蛭素的全血模型，在不同炎症途径之间进行相互作用，该抗凝剂不会干扰补体系统。组织因子、细胞黏附分子的表达以及氧化爆发高度依赖于C5，通过激活产物C5a介导，而粒细胞酶的释放主要依赖于C3且不依赖于C5a。细胞因子和趋化因子的释放不同程度地由补体和CD14介导；例如，白细胞介素（IL）-1β和IL-8比IFN-γ和IL-6更依赖于补体，而IFN-γ和IL-6高度依赖于CD14。IL-1受体拮抗剂（IL-1ra）和IFN-γ诱导蛋白10（IP-10）完全依赖于CD14且受补体反向调节，即补体缺陷和补体抑制会增强它们的释放。粒细胞反应主要依赖于补体，而单核细胞反应更依赖于CD14。值得注意的是，补体和CD14的联合中和可消除所有反应。本研究为补体在人类对革兰氏阴性菌炎症反应中的综合作用提供了重要见解。
