Complement C3

Immunoturbidimetry assay

Product description:

The complement system is a part of the innate immune system that enhances (complements) the ability of antibodies and phagocytes to clear microbes and damaged cells from an organism, promote inflammation, and attack the pathogen's cell membrane. The complement system consists of more than 30 proteins that are either present as soluble proteins in the blood or are present as membrane-associated proteins. Most of the proteins and glycoproteins that constitute the complement system are synthesized by hepatocytes and also a substantial amounts by tissue macrophages, blood monocytes, and epithelial cells of the genitourinary system and gastrointestinal tract. Activation of complement leads to a sequential cascade of enzymatic reactions; the complement activation pathways, resulting in the formation of the potent anaphylatoxins C3a and C5a that elicit a plethora of physiological responses that range from chemo-attraction to apoptosis.

Complement activation is known to occur through three different pathways: alternate, classical and lectin involving proteins that mostly exist as inactive zymogens that are then sequentially cleaved and activated. All the pathways converge at C3; the most abundant complement protein found in the blood, resulting in the formation of the activation products, C3a, C3b, C5a and the membrane attack complex (C5b-9).

The classical pathway (CP) is initiated when immune complexes are formed after IgG or IgM binding to pathogens or to other foreign and non-self-antigens. C4 is the second component reacting in the classical pathway cascade. Most synthesis occurs in the hepatic parenchymal cells, although some C4 may be synthesized by monocytes or other tissues. C4 levels in plasma rise modestly after trauma or inflammation and tissue necrosis (acute phase process). Inherited primary deficiency of C4 is associated with a high prevalence of autoimmune or collagen vascular disease, particularly Systemic Lupus Erythematosus (SLE). Also, levels of C4 are more commonly depressed because of its consumption as a consequence of formed immune-complexes.