Anti-C4 antibody [16D2]

Supplementary info

This supplementary information is collated from multiple sources and compiled automatically.

Activity summary

Complement component 4 (C4) is a significant protein in the complement system also known as C4 complement. C4 has a molecular mass of approximately 206 kDa and mainly expresses in the liver. It is present in the blood plasma. C4 plays an important role in the immunological response and activates classical and lectin complement pathways. It serves a mechanical function by binding to pathogen surfaces and facilitating the cleavage that leads to the downstream activation of the complement cascade. There's a C4 ELISA test that allows for quantifying C4 levels in serum which is important for clinical diagnostics.

Biological function summary

Complement C4 participates in the immune defense by marking pathogens for destruction and enhancing phagocytosis. C4 is a part of a complex with other complement proteins like C3 and C1 to initiate the formation of the C3 convertase enzyme. This action amplifies the immune response leading to the clearance of microorganisms and apoptotic cells. C4 also plays a role in regulating the inflammation process maintaining homeostasis in the immune system.

Pathways

C4 fits into the complement activation pathway specifically the classical and lectin pathways. These pathways are important for innate immunity and connect with components like complement C3 and complement C1. Through the classical pathway C4 gets activated after binding to antibodies that have recognized antigens leading to a chain reaction that strengthens the immune response. The lectin pathway also requires C4 activation through different stimuli solidifying C4's central role in immune system signaling networks.

Associated diseases and disorders

Abnormal C4 activity associates with autoimmune diseases like systemic lupus erythematosus (SLE) and rheumatoid arthritis. Low levels of complement C4 in serum can indicate these autoimmune conditions where the immune system mistakenly attacks its own tissues. C4 also connects to other proteins like complement component C1q in the context of SLE. C4 deficiencies or abnormalities may contribute to the development or exacerbation of these diseases highlighting its importance in disease pathogenesis and highlighting its value as a target for diagnostic tests such as C4 ELISA or serum complement tests.