C3b is the larger of two elements formed by the cleavage of complement component 3, and is considered an important part of the innate immune system. C3b is potent in opsonization: tagging pathogens, immune complexes (antigen - antibody), and apoptotic cells for phagocytosis.

Aug 10, 2006 · Central to the complement system is the activated form of C3, called C3b, which attaches covalently to target surfaces to amplify complement response, label cells for phagocytosis and stimulate the adaptive immune response.

C3b is central to the function of all three pathways of complement (Law, S.K.A. and Reid, K.B.M. (1995)). Initiation of each pathway generates proteolytic enzyme complexes (C3 convertases) which are bound to the target surface.

Jan 14, 2025 · C3b opsonization enhances the immune system’s ability to identify and eliminate pathogens. This process begins when C3b, a fragment of the complement protein C3, binds to the surface of a pathogen. This binding is a specific interaction that occurs when C3b recognizes molecular patterns on the pathogen’s surface.

3 days ago · Deposition of C3b/C4b on healthy cells is limited by proteolytic inactivation through Factor I (FI) and its co-factors, including factor H (FH), C4b binding protein (C4BP), CD46, and CR1. Regulators with decay-accelerating activity, notably FH, C4BP, CD46, CR1, and CD55, further degrade C3 and C5 convertases if they form inappropriately.

C3b is a highly unstable molecule that has a unique thioester that allows covalent binding to a microbial cell. Some C3b fragments bind to the target cell, where they act as opsonins. In the classic pathway, most C3b is found in an AbC4bC2aC3b complex on the cell surface, which is called the C5 convertase .

Oct 15, 2006 · Complement component 3 (C3) occupies a central position because of the manifold biological activities of its activation fragments, including the major fragment, C3b, which anchors the...

Complement component 3, often simply called C3, is a protein of the immune system that is found primarily in the blood. It plays a central role in the complement system of vertebrate animals and contributes to innate immunity. In humans it is encoded …

Dec 12, 2006 · C3 plays a central role in the activation of the complement system. Its processing by C3 convertase is the central reaction in both classical and alternative complement pathways. After activation C3b can bind covalently, via its reactive thioester, to cell surface carbohydrates or immune aggregates.

Complement Component C3b is a serum protein that plays a crucial role in innate and adaptive immunity by binding covalently to pathogens, acting as an opsonin to target them for destruction by phagocytes.