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Regulators and receptors of the complement system

M Kathryn Liszewski, PhD
John P Atkinson, MD
Section Editors
E Richard Stiehm, MD
Peter H Schur, MD
Deputy Editor
Anna M Feldweg, MD


Precise control of the complement system is necessary because of its potent proinflammatory and cellular destructive capabilities. The regulation of the complement system will be reviewed here. In order to fully comprehend the functions of the various regulatory proteins, it is helpful to be familiar with the complement pathways, which are reviewed elsewhere. (See "Complement pathways".)


Nearly one-half of all complement proteins serve a regulatory function [1-4]. The goal of regulation is to prevent complement damage to normal host tissue (inappropriate or wrong target) and fluid-phase activation (no target) [5]. Deficiencies of control proteins lead to excessive complement activation and significant morbidity and mortality. (See "Inherited disorders of the complement system".)

Regulatory proteins inhibit the system by destabilizing activation complexes and by mediating specific proteolysis of activation-derived fragments. The complement pathways are regulated at the following critical steps:

Activation or initiation

Amplification (convertase formation)

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Literature review current through: Oct 2017. | This topic last updated: Oct 31, 2016.
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