Complement System - Role in Disease

Role in Disease

It is thought that the complement system might play a role in many diseases with an immune component, such as Barraquer-Simons Syndrome, asthma, lupus erythematosus, glomerulonephritis, various forms of arthritis, autoimmune heart disease, multiple sclerosis, inflammatory bowel disease, and ischemia-reperfusion injuries. and rejection of transplanted organs.

The complement system is also becoming increasingly implicated in diseases of the central nervous system such as Alzheimer's disease and other neurodegenerative conditions such as spinal cord injuries.

Deficiencies of the terminal pathway predispose to both autoimmune disease and infections (particularly Neisseria meningitidis, due to the role that the membrane attack complex plays in attacking Gram-negative bacteria).

Mutations in the complement regulators factor H and membrane cofactor protein have been associated with atypical haemolytic uraemic syndrome. Moreover, a common single nucleotide polymorphism in factor H (Y402H) has been associated with the common eye disease age-related macular degeneration. Polymorphisms of complement component 3, complement factor B, and complement factor I, as well as deletion of complement factor H-related 3 and complement factor H-related 1 also affect a person's risk of developing age-related macular degeneration. Both of these disorders are currently thought to be due to aberrant complement activation on the surface of host cells.

Mutations in the C1 inhibitor gene can cause hereditary angioedema, an autoimmune condition resulting from reduced regulation of the complement pathway.

Mutations in the MAC components of complement, especially C8, are often implicated in recurrent Neisserial infection.

Diagnostic tools to measure complement activity include the total complement activity test.