The plasma contact system is the initiator of the intrinsic pathway of coagulation and the main producer of the inflammatory peptide bradykinin. When plasma is exposed to a negatively charged surface the two enzymes factor XII (FXII) and plasma prekallikrein (PK) bind to the surface alongside the co-factor high molecular weight kininogen (HK), where PK is non-covalently bound to. Here, FXII and PK undergo a reciprocal activation feedback loop that leads to full contact system activity in a matter of seconds. Although naturally occurring negatively charged surfaces have shown to be involved in the role of the contact system in thrombosis, such surfaces are elusive in the pathogenesis of bradykinin-driven hereditary angioedema (HAE). In this review, we will explore the molecular mechanisms behind contact system activation, their assembly on the endothelial surface, and their role in the HAE pathophysiology.

血浆接触系统是凝血内在途径的发起者和炎症肽缓激肽的主要生产者。当血浆暴露于带负电荷的表面时，两种酶因子 XII (FXII) 和血浆前激肽释放酶 (PK) 与辅因子高分子量激肽原 (HK) 一起结合到表面，其中 PK 非共价结合。在这里，FXII 和 PK 经历一个相互的激活反馈循环，导致在几秒钟内完全接触系统活动。尽管天然存在的带负电表面已显示与接触系统在血栓形成中的作用有关，但此类表面在缓激肽驱动的遗传性血管性水肿 (HAE) 的发病机制中是难以捉摸的。在这篇综述中，我们将探索接触系统激活背后的分子机制，