The complement cascade consists of cell bound and serum proteins acting together to protect the host from pathogens, remove cancerous cells and effectively links innate and adaptive immune responses. Despite its usefulness in microbial neutralization and clearance of cancerous cells, excessive complement activation causes an immune imbalance and tissue damage in the host. Hence, a series of complement regulatory proteins present at a higher concentration in blood plasma and on cell surfaces tightly regulate the cascade. The complement cascade can be initiated by B-1 B cell production of natural antibodies. Natural antibodies arise spontaneously without any known exogenous antigenic or microbial stimulus and protect against invading pathogens, clear apoptotic cells, provide tissue homeostasis, and modulate adaptive immune functions. Natural IgM antibodies recognize microbial and cancer antigens and serve as an activator of complement mediated lysis. This review will discuss advances in complement activation and regulation in bacterial and viral infections, and cancer. We will also explore the crosstalk of natural antibodies with bacterial populations and cancer.

中文翻译：

---

对感染和癌症的体液先天免疫反应的驱动者和调节者。


补体级联由细胞结合蛋白和血清蛋白组成，共同作用以保护宿主免受病原体侵害、清除癌细胞并有效连接先天性免疫反应和适应性免疫反应。尽管补体在中和微生物和清除癌细胞方面很有用，但过度的补体激活会导致宿主免疫失衡和组织损伤。因此，血浆中和细胞表面上以较高浓度存在的一系列补体调节蛋白严格调节级联。补体级联可由 B-1 B 细胞产生天然抗体来启动。天然抗体在没有任何已知的外源抗原或微生物刺激的情况下自发产生，可防止病原体入侵、清除凋亡细胞、提供组织稳态并调节适应性免疫功能。天然 IgM 抗体可识别微生物和癌症抗原，并作为补体介导的裂解的激活剂。这篇综述将讨论细菌和病毒感染以及癌症中补体激活和调节的进展。我们还将探索天然抗体与细菌群体和癌症的相互作用。