Other complement proteins promote inflammation . This response of tissues to damage is protective, but it can also amplify the initial damage and cause much suffering. These are all caused not by pathogens but by chemical signals produced in animal bodies. They provide a fast response to tissue damage or invasion by bacteria. Damage provokes leaks in capillaries.
Complement proteins invade the site.
They both attack bacterial invaders directly and attract phagocytic white blood cells. Mast cells resident in the tissues are then stimulated to release vasodilators, which increases blood flow to the region. The result is a mess which typically moves a human in an industrialized nation to go to the doctor. Before the evolution of M.D.s, however, it is likely that inflammation served to notify the owner of the infected body part to take it easy. This complex set of interactions, however, is still quite nonspecific.