Department of Orthopaedic Trauma, Hand, Plastic and Reconstruction Surgery, University of Ulm, 89081 Ulm, Germany.
Semin Immunol. 2013 Feb;25(1):73-8. doi: 10.1016/j.smim.2013.05.006. Epub 2013 Jun 13.
The complement system, as part of innate immunity, is activated immediately after trauma in response to various pathogen- and danger-associated molecular patterns (PAMPs and DAMPs), and helps to eliminate microorganisms and damaged cells. However, recent data indicate an extended role of complement far beyond pure "killing", which includes regulation of the cytokine/chemokine network, influencing physiological barriers, interaction with the coagulation cascade, and even involvement with bone metabolism and repair. Complement-induced hyper-activation and dysfunction reveal the dark side of this system, leading to complications such as sepsis, multiple-organ dysfunction, delayed fracture healing, and unfavorable outcome. Thus, the present review focuses on less known regulatory roles of the complement system after trauma and during fracture healing, rather than on its bacterial and cellular "killing functions". In particular, various complement crosstalks after trauma, including the coagulation cascade and apoptosis system, appear to be crucially involved early after trauma. Long-term effects of complement on tissue regeneration after fracture and bone turnover are also considered, providing new insights into innate immunity in local and systemic complement-driven effects after trauma.
补体系统作为先天免疫系统的一部分，在创伤后立即被激活，以响应各种病原体和危险相关的分子模式（PAMPs 和 DAMPs），并有助于消除微生物和受损细胞。然而，最近的数据表明，补体的作用远远超出了纯粹的“杀伤”作用，包括调节细胞因子/趋化因子网络、影响生理屏障、与凝血级联相互作用，甚至参与骨代谢和修复。补体诱导的过度激活和功能障碍揭示了该系统的阴暗面，导致并发症，如败血症、多器官功能障碍、骨折愈合延迟和不良预后。因此，本综述重点介绍创伤后和骨折愈合期间补体系统鲜为人知的调节作用，而不是其对细菌和细胞的“杀伤作用”。特别是，创伤后各种补体相互作用，包括凝血级联和细胞凋亡系统，似乎在创伤后早期就起着至关重要的作用。补体对骨折后组织再生和骨转换的长期影响也被考虑在内，为创伤后局部和全身补体驱动效应中的先天免疫提供了新的见解。
