Complement system

Complement System

The Complement System (pronunciation: /ˈkɒmplɪmənt/ system) is a part of the immune system that enhances (complements) the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism, promotes inflammation, and attacks the pathogen's cell membrane.

Etymology

The term "complement" comes from the Latin word 'complementum', meaning 'something that completes'. It was coined in the late 19th century by the German bacteriologist Paul Ehrlich to denote the activity in serum that completes the action of antibodies.

Components

The complement system consists of a number of small proteins found in the blood, generally synthesized by the liver, and normally circulating as inactive precursors (pro-proteins). When stimulated by one of several triggers, proteases in the system cleave specific proteins to release cytokines and initiate an amplifying cascade of further cleavages.

Functions

The major functions of the complement system include:

Lysis of infectious organisms
Phagocytosis
Inflammation
Immune clearance

Related Terms

Antibody: A protein produced by the body's immune system when it detects harmful substances.
Phagocytic cells: Cells that protect the body by ingesting harmful foreign particles, bacteria, and dead or dying cells.
Microbes: Microscopic organisms, which may be single-celled or multicellular.
Inflammation: A localized physical condition in which part of the body becomes reddened, swollen, hot, and often painful, especially as a reaction to injury or infection.
Cell membrane: The semipermeable membrane surrounding the cytoplasm of a cell.
Immune system: The bodily system that protects the body from foreign substances, cells, and tissues.
Liver: A large lobed glandular organ in the abdomen of vertebrates, involved in many metabolic processes.
Cytokines: Any of a number of substances, such as interferon, interleukin, and growth factors, which are secreted by certain cells of the immune system and have an effect on other cells.