This is part of the body's defence mechanism that comprises a series of 20 serum PEPTIDES. These are sequentially activated to produce three significant effects: firstly, the release of small peptides which provoke inflammation and attract PHAGOCYTES; secondly, the deposition of a substance (component C3b) on the membranes of invading bacteria or viruses, attracting phagocytes to destroy the microbes; thirdly, the activation of substances that damage cell membranes – called lytic components – which hasten the destruction of ‘foreign’ cells. (See IMMUNOLOGY.)