Question

What do complement proteins do?

Answer 1

The complement system is a part of the immune system that enhances (complements) the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism, promotes inflammation, and attacks the pathogen's cell membrane.

Answer 2

Complement is a system of plasma proteins
than can be activated directly by pathogen or indirectly by pathogen-bound antibody,leading to a cascade of reactions that occurs on the surface of pathogens and generate active components with various effecter form.
complement system is a part of immune system.