What role does the complement system play in immunity?

The complement system plays a crucial role in the immune response by enhancing the ability of antibodies and phagocytic cells to clear pathogens. This system consists of a series of proteins that circulate in the bloodstream and are activated in response to pathogens. When these proteins are activated, they can opsonize pathogens, which marks them for destruction by phagocytes, such as macrophages and neutrophils. Opsonization increases the efficiency of phagocytosis, helping the immune system to eliminate bacteria and other foreign invaders more effectively.

Additionally, the complement system can lead to the formation of membrane attack complexes that create pores in the pathogens' membranes, leading to cell lysis. The recruitment and activation of inflammatory cells also occur, amplifying the immune response. Overall, the complement system serves as an important bridge between innate and adaptive immunity by enhancing both antibody action and the activity of phagocytes, making it a vital component in the defense against infections.