Biological Function:

Complement helps the immune system get rid of foreign invaders via several mechanisms.

1. phagocytosis: macrophages in the liver have receptors for C3b.

2. cytolysis:if C9 is bound cells will lyse.

3. chemotaxis: Some complement fragments (C3a, C5a, C567) are chemotactic and can cause the migration of wbc to the site of an infection.

4. anaphylaxis: C3a and C5a fragments can cause the release of vasoactive substances such as histamine from mast cells.

Biological Function