In this article, we will discuss Complement System. So, let’s get started.
Complement was first discovered as a heat-labile component of normal plasma that was found to add to or augment the opsonization of bacteria by antibodies and facilitate bacterial killing. The name derives from the fact that this system was found to complement the antibacterial activity of the antibody. Complement system is an important part of the innate and adaptive immune responses.
• It is constituted by a collection of 30 different proteins, which include serum and cell surface proteins as well as cell membrane receptors.
• The complement proteins, in their precursor zymogen forms, are widely distributed throughout body fluids and tissues without any adverse effect. They are activated at sites of infection or injury, however, to trigger a series of potent inflammatory events. Their action occurs via three pathways:
1. Classical pathway
2. Alternative pathway
3. Mannose-binding lectin pathway or MBL-MASP (MBL- associated serine proteases; homologous to the classical pathway.