C3b: A Crucial Player in the Complement System for Immune Defense and Pathogen Clearance

C3b

binds to the surfaces of microorganisms and phagocyte receptors.

C3b is a fragment of the third component of the complement system, C3. It is formed by the cleavage of C3 by the enzymatic activity of either C3bBb convertase or C4b2b3b convertase. C3b plays a critical role in activating the complement cascade, one of the body’s defense systems against pathogens.

Once C3b is formed, it can bind covalently to the surface of microbes, enhancing the opsonization of the pathogen. Opsonization refers to the process where antibodies or complement proteins bind to pathogens, marking them for recognition and removal by immune cells. In addition to opsonization, C3b can also participate in the formation of the membrane attack complex (MAC), which can lyse and kill certain pathogens.

C3b also acts as a mediator of inflammation. It can attract immune cells to the site of infection or injury by binding to complement receptors on leukocytes. The recruitment of immune cells to the site of inflammation is essential for the destruction of pathogens and for the initiation of tissue repair.

Overall, C3b plays a crucial role in the complement system by activating and coordinating the immune response against pathogens and participating in the clearance and removal of these pathogens from the body.

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