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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. Some studies estimate that less than 10% are identified. [5]
Complement tests C4 ... Complement 4 deficiency is a genetic condition affecting complement component 4. [1] It can present with lupus-like symptoms. [2 ...
Terminal complement pathway deficiency is a genetic condition affecting the complement membrane attack complex (MAC). It involves deficiencies of C5, C6, C7, and C8. (While C9 is part of the MAC, and deficiencies have been identified, [1] it is not required for cell lysis. [2]) People with this condition are prone to meningococcal infection. [3]
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.
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.
Humoral immune deficiency (including B cell deficiency or dysfunction), with signs or symptoms depending on the cause, but generally include signs of hypogammaglobulinemia (decrease of one or more types of antibodies) with presentations including repeated mild respiratory infections, and/or agammaglobulinemia (lack of all or most antibody production) which results in frequent severe infections ...
Excessive complement activity contributes to severe Covid-19 symptoms and disease. [53] Although complement is intended to protect the body systems, under stress there can be more damage than protection. Research has suggested that the complement system is manipulated during HIV/AIDS, in a way that further damages the body. [54]