About Complement Proteins.....

Question

Could someone please just briefly clarify for me the process of Complement Protein Action in the immune response? Do Chemotoxins have anything to do with it? Thanks.

Answer 1

Complement is a group of serum proteins which work with (complement) antibody activity to eliminate pathogens. Complement is NOT antigen-specific and it is activated immediately in the presence of pathogen, so it is considered part of innate immunity. However, antibody activates some complement proteins, so complement activation is also part of humoral immunity. Complement stimulates inflammation, facilitates antigen phagocytosis, and lyses some cells directly. Because it is such a powerful inflammatory agent, its activity is tightly regulated.

Complement proteins are produced constitutively by macrophages and hepatocytes, and are present in the circulation as inactive molecules. Several complement proteins are pro-enzymes. When activated, they become proteases that cut peptide bonds in other complement proteins to activate them in turn. Since each activated protease can activate many substrate molecules, the initial activation is rapidly amplified to produce millions of effector molecules (a cascade).