Final answer:
The complement system consists of approximately 20 proteins that operate in a cascading manner to target and eliminate pathogens. It marks pathogens for phagocytosis (opsonization) and can directly kill them by forming membrane attack complexes that lyse the pathogen cells.
Step-by-step explanation:
The complement system is an essential part of the immune system that aids in protecting the body against microbial invaders. It consists of a group of proteins that work together in a cascading fashion to identify, mark, and destroy extracellular pathogens. These proteins, synthesised mainly by liver cells and macrophages, are present in the blood as inactive forms and are activated when there is an infection or by the activity of the adaptive immune system.
Opsonization is one of the primary functions of the complement system, where complement proteins act as markers to facilitate the phagocytosis of pathogens by cells like macrophages and B cells. Additionally, some complement proteins form membrane attack complexes that create pores in the cell membranes of pathogens, leading to their lysis and destruction.
Overall, the complement system enhances the body's antibody response and serves as part of both the innate and adaptive immune systems, effectively complementing other immune mechanisms.