Process of coating of pathogen for efficient phagocytosis is known as: September 2011
Correct Answer: Opsonization
Description: Ans. D: Opsonization Phagocytosis is largely responsible for depletion of cells coated with antibodies Cells opsonized by the IgG antibodies are recognized by phagocyte Fc receptors, which are specific for the Fc poions of some IgG subclasses Agglutination When a paiculate antigen is mixed with its antibody in the presence of electrolytes at a suitable temperature and pH, the paicles are clumped or agglutinated Transduction Transfer of a poion of the DNA from one bacterium to another by a bacteriophage Conjugation It is .a process by whereby a 'male' or 'donor' bacterium 'mates' or makes a physical contact with a 'female' or 'recipient' bacterium and transfers genetic element into it Opsonization It is the process by which a pathogen is marked for ingestion and destruction by a phagocyte. Opsonization involves the binding of an opsonin, e.g., antibody, to a receptor on the pathogen's cell membrane. After opsonin binds to the membrane, phagocytes are attracted to the pathogen. The Fab poion of the antibody binds to the antigen, whereas the Fc poion of the antibody binds to an Fc receptor on the phagocyte, facilitating phagocytosis. The receptor-opsin complex can also create byproducts like C3b and C4b which are impoant components of the complement system. These components are deposited on the cell surface of the pathogen and aid in its destruction. The cell can also be destroyed by a process called antibody-dependent cellular cytotoxicity, in which the pathogen does not need to be phagocytosed to be destroyed. During this process, the pathogen is opsonized and bound with the antibody IgG its Fab domain. Then the antibody binds an immune effector cell its Fc domain and this binding triggers a release of lysis products from the bound immune effector cell (monocytes, neutrophils, eosinophils and natural killer cells). This process can cause inflammation of surrounding tissues and damage to healthy cells. Opsonin It is any molecule that targets an antigen for an immune response. However, the term is usually used in reference to molecules that act as a binding enhancer for the process of phagocytosis, especially antibodies, which coat the negatively-charged molecules on the membrane. Molecules that activate the complement system are also considered opsonins. Phagocytic cells do not have an FC receptor for IgM, making IgM ineffective in assisting phagocytosis. However, IgM is extremely efficient at activating complement and is, therefore, considered an opsonin. Opsonins can also refer to molecules that target a cell for destruction through the action of Natural Killer cells. Examples of opsonin molecules include: Antibodies: IgG Components of the complement system: C3b, C4b, and iC3b Mannose-binding lectin (initiates the formation of C3b) The most impoant are IgG and C3b.
Category:
Microbiology
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