Complement component 6

Complement component 6 (C6) is a protein that plays a crucial role in the immune system, particularly in the complement system, which is a part of the innate immune response. C6 is involved in the formation of the membrane attack complex (MAC), a structure that creates pores in the membranes of target cells, leading to their lysis and death. This process is essential for the defense against pathogens, such as bacteria and viruses, but also plays a role in certain diseases when improperly regulated.

Structure and Function

C6 is a glycoprotein that is part of the terminal complement pathway. It interacts with other complement components, including C5, C7, C8, and C9, to form the MAC. The activation of C6 occurs after the cleavage of C5 into C5a and C5b; C5b then binds to C6, initiating the assembly of the MAC. This complex embeds itself into the membrane of target cells, leading to cell lysis.

Genetic and Molecular Basis

The gene encoding C6 is located on human chromosome 5. Mutations in this gene can lead to deficiencies in the C6 protein, which can result in increased susceptibility to certain infections, particularly those caused by Neisseria bacteria, due to the inability to form an effective MAC.

Clinical Significance

C6 deficiency is a rare condition but can have significant clinical implications. Individuals with this deficiency are at a higher risk of developing recurrent infections, especially meningitis, caused by Neisseria meningitidis. Diagnosis of C6 deficiency involves measuring the levels of complement proteins in the blood and assessing the functional activity of the complement system.

In addition to its role in defense against pathogens, the complement system, including C6, has been implicated in the pathogenesis of various autoimmune and inflammatory diseases. Dysregulation of complement activation can lead to tissue damage and disease. Therapeutic interventions targeting the complement system are being explored as potential treatments for these conditions.

Treatment and Management

Management of C6 deficiency primarily involves prevention and treatment of infections. Vaccination against Neisseria meningitidis is recommended for individuals with C6 deficiency to reduce the risk of meningitis. Antibiotic prophylaxis may also be considered in some cases. For diseases associated with complement dysregulation, treatments that target specific components of the complement system, including C6, are under investigation.

See Also

• Complement system
• Membrane attack complex
• Innate immune system
• Autoimmune diseases