Write down the functions of complement in inflammation.

Complement:

The complement system is a collection of soluble proteins and membrane receptors that function mainly in host defense against microbes and in pathologic inflammatory reactions.

Functions:

• Increase vascular permeability: C3a C5a and to a lesser extent C3a stimulate histamine release from mast cells and thereby increase vascular permeability and cause vasodilation. They are also called anaphylatoxins because they have effects similar to those of mast cell mediators that involved in the reaction called anaphylaxis.
• Chemotaxis: C5a is a chemotactic agent for neutrophil, monocyte, eosinophils and basophils. C5a also activate lipoxygenase pathway of Arachadonic acid metabolism in neutrophils and monocytes causing further release of inflammatory mediators.
• Opsonization and phagocytosis: C3b and its cleavage product iC3b when fixed to microbial cell wall, acts as opsonins and promote phagocytosis by neutrophils and macrophages.
• Cell lysis: The deposition of the MAC on cells makes these cells permeable to water and ions and results in death of the cell.