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How does complement make bacteria easier for phagocytes to destroy?

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Pathways of complement activation — inflammation The main function of complement proteins is to aid in the destruction of pathogens by piercing their outer membranes (cell lysis) or by making them more attractive to phagocytic cells such as macrophages (a process known as opsonization). Some complement components also promote inflammation by stimulating cells to release histamine and by attracting phagocytic cells to the site of infection.

The complement system facilitates the destruction of bacteria by phagocytes primarily through a process known as opsonization.1

When the complement system is activated, the protein C3 is cleaved, producing a fragment called C3b. Large numbers of C3b molecules deposit onto the surface of the invading microorganism. This coating acts as a signal that makes the bacteria significantly more attractive to phagocytic cells, such as macrophages and neutrophils.21

Phagocytes possess specific receptors on their surfaces that recognize and bind to the C3b molecules attached to the pathogen. This binding interaction stimulates the phagocyte to ingest the microorganism, which is subsequently destroyed by the phagocyte's digestive enzymes. By effectively "tagging" the bacteria, the complement system ensures that phagocytes can more efficiently locate, bind to, and eliminate the infectious agents.12