Question

How is the complement cascade initiated and effector functions of C3b and membrane attack complex, and anaphylatoxin c3a and c5a. Please write in complete sentences and explain in detail. Thank you!

Answer 1

The complement pathways are activated by antigen antibody complexes also known as specific immune response with the antibody isotype IgG and IgM. The classical complement pathway is one if the three system that activates the conplement system that is the immune system. Once it is activated the protein series are also activated. Here the series of proteins are recruited to generate C3 convertase (C4bC2a), which cleaves the C3 protein. The C3b component of the cleaved C3 binds to C3 convertase (C4bC2a) to generate C5 convertase(C4bC2aC3b), which cleaves the C5 protein. The cleaved products attract phagocytes to the site of infection and tags target cells for elimination by phagocytosis. In addition, the C5 convertase initiates the terminal phase of the complement system, leading to the assembly of the membrane attack complex (MAC). The membrane attack complex creates a pore on the target cell's membrane, inducing cell lysis and death.

The classical complement pathway can also be activated by apoptotic cells, necrotic cells, and acute phase proteins.