The complement system is a complex cascade involving proteolytic cleavage of serum glycoproteins often activated by cell receptors. This cascade ultimately results in induction of the inflammatory response, phagocyte chemotaxis and opsonization, and cell lysis.A complex of complements C5b, C6, C7, and C8 mediates the polymerization of up to eighteen C9 molecules into a tube-like membrane attack complex that is inserted into the plasma membrane of unwanted organisms, such as of Gram-negative bacteria and viral infected cells. This channel through the lipid bilayer results in lysis of the cell.Human Complement C7 is a β-2-globulin, which is composed of a single polypeptide chain. The initial binding of C7 and C6 to C5b is thought to form a stable complex for subsequent binding of C8 and C9. The resulting activated complex is responsible for membrane attack and lysis.
