Complement is a key component of the innate immune defence and in addition forms a bridge to the adaptive immune responses. As such complement is of vital importance for efficient protection against infections. However, the activity of the complement system can also aberrantly be directed against the tissues of the body itself and contribute to organ damage in a variety of diseases. In several rheumatic diseases complement activation is suggested to play a pronounced role. This review will highlight the role of both complement activation and complement regulation in rheumatic disease.

A contribution of complement to the disease process is often suggested based on the presence of complement activation fragments in the target tissues or the presence of complement activation fragments in the circulation. The role that complement plays in different rheumatic diseases is often unknown but is thought to contribute to tissue damage as a consequence of autoantibody mediated immune complex formation and deposition. In addition reduced complement inhibition mediated by endogenous complement regulators can also enhance complement activity and tissue damage. In observational studies, it is difficult to distinguish whether complement activation is a result of enhanced activation or decreased regulation. Until recently, strong conclusions on the relative importance of complement activation to the pathology were largely restricted to animal experiments. Usage of complement targeting therapeutics in humans will hopefully give us the opportunity to study the actual contribution of complement activation towards disease progression and tissue damage in rheumatic disease into more detail.

补体是先天免疫防御的关键组成部分，此外还构成了适应性免疫应答的桥梁。因此，补体对于有效预防感染至关重要。然而，补体系统的活性也可以异常地针对身体自身的组织，并在多种疾病中导致器官损伤。在几种风湿性疾病中，补体激活被认为起着明显的作用。这篇综述将强调补体激活和补体调节在风湿性疾病中的作用。

通常基于靶组织中补体激活片段的存在或循环中补体激活片段的存在来建议补体对疾病过程的贡献。补体在不同风湿性疾病中所起的作用通常是未知的，但由于自身抗体介导的免疫复合物的形成和沉积，据认为会导致组织损伤。此外，由内源性补体调节剂介导的补体抑制作用的降低也可以增强补体活性和组织损伤。在观察性研究中，很难区分补体激活是增强激活还是调节降低的结果。直到最近，关于补体激活对病理学的相对重要性的强有力的结论主要限于动物实验。有望在人类中使用补体靶向治疗剂，这将使我们有机会更详细地研究补体激活对风湿性疾病中疾病进展和组织损伤的实际贡献。