All of the following are Opsonins, Except
Leukotriene B4 (LTB4) is not an Opsonin. The major opsonins are IgG antibodies, the C3b breakdown product of complement , and ceain plasma lectin , notably mannose-binding lectin, all of which are recognized by specific receptors on leukocytes. Three major Opsonins IgG Opsonin (The Fc Fragment of immunoglobulin G) C3b Opsonin is the fragment generated by activation of complement pathway Lectins are carbohydrate-binding proteins in the plasma which bind to bacterial cell wall. Opsonisation with Opsonins: Opsonins are specific proteins in the serum that enhance the process of phagocytosis by coating the surface of target bacteria or microorganisms. This process is called opsonisation (meaning preparing for eating). Opsonins establish a bond between bacteria and the cell membrane of phagocytic cell. If the surface of the target is prepared (opsonized) by plasma proteins, phagocytosis is made easier, though some targets can be taken up without this coating. The efficiency of phagocytosis is greatly enhanced when microbes are opsonized by these proteins Phagocytes such as Neutrophils express high affinity receptors for opsonin protein. Neutrophils have membrane receptors for IgG and C3b. These are three major types of Opsonins: IgG antibody C3b fragment of Complement Non-specific opsonins This is the most impoant opsonin IgG antibody works like a ligand. The Fab pa of the globulin binds to the surface of the microorganism while the Fc poion sticks out and fits into the membrane receptors of the phagocyte Benign Fragment of C3, C3b is set free when complement is activated Like IgG, C3b has a tail end that fits into a receptor on the surfaces of phagocytic cells Several proteins have opsonic propeies Lectins (Mannose-Binding Lectins) are carbohydrates binding proteins in the plasma which bind to bacterial cell wall C-reactive protein Hageman Factor Serum amyloid A Ref: Robbins 9th edition Pgno: 78
IgG
C3b
LTB4
Mannose binding Lectin
General pathology