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Complement deficiency is an immunodeficiency of absent or suboptimal functioning of one of the complement system proteins. [4] Because of redundancies in the immune system , many complement disorders are never diagnosed.
Complement component 4 (C4), in humans, is a protein involved in the intricate complement system, originating from the human leukocyte antigen (HLA) system. It serves a number of critical functions in immunity, tolerance, and autoimmunity with the other numerous components.
Complement 4 deficiency is a genetic condition affecting complement component 4. [1] It can present with lupus-like symptoms. [2]
For example, if and individual has normal C3/C4 values but a decreased CH50, that can indicate a terminal complement pathway deficiency while if one has low C3 and CH50 values that can indicate an autoimmune condition such as systemic lupus erythematosus.
The trimer provides a surface for interaction between the antigen-antibody complex and other complement components. The alpha chain may be cleaved to release C4 anaphylatoxin, a mediator of local inflammation. Deficiency of this protein is associated with systemic lupus erythematosus and type I diabetes mellitus.
Diagnosis usually consists of medical evaluation in addition to laboratory testing. Laboratory evaluation includes complement studies, in which typical cases demonstrate low C4 levels, low C1q levels, and normal C3 levels. [3] Determining the etiology, or cause, of acquired angioedema is often helpful in providing appropriate management of AAE.
Lack of regulation of the classical complement pathway through the deficiency in C1-inhibitor results in episodic angioedema. [1] C1-inhibitor defiency can be hereditary or acquired, resulting in hereditary or acquired angioedema. [12] C1-inhibitor plays the role of inactivating C1r and C1s to prevent further downstream classical complement ...
Scheme of the complement system. The complement system, also known as complement cascade, is a part of the humoral, innate immune system and enhances (complements) the ability of antibodies and phagocytic cells to clear microbes and damaged cells from an organism, promote inflammation, and attack the pathogen's cell membrane. [1]