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The water-accessible surface area of an IgG antibody. Immunoglobulin G (IgG) is a type of antibody. Representing approximately 75% of serum antibodies in humans, IgG is the most common type of antibody found in blood circulation. [1] IgG molecules are created and released by plasma B cells. Each IgG antibody has two paratopes.
Antibody (or immunoglobulin) structure is made up of two heavy-chains and two light-chains.These chains are held together by disulfide bonds.The arrangement or processes that put together different parts of this antibody molecule play important role in antibody diversity and production of different subclasses or classes of antibodies.
Free immunoglobulin light chains secreted by neoplastic plasma cells, such as in multiple myeloma, can be called Bence Jones protein when detected in the urine, although there is a trend to refer to these as urinary free light chains. Increased levels of free Ig light chains have also been detected in various inflammatory diseases.
Mechanism of class-switch recombination that allows isotype switching in activated B cells. Immunoglobulin class switching, also known as isotype switching, isotypic commutation or class-switch recombination (CSR), is a biological mechanism that changes a B cell's production of immunoglobulin from one type to another, such as from the isotype IgM to the isotype IgG. [1]
Each antibody binds to a specific antigen in a highly specific interaction analogous to a lock and key.. An antibody (Ab) or immunoglobulin (Ig) is a large, Y-shaped protein belonging to the immunoglobulin superfamily which is used by the immune system to identify and neutralize antigens such as bacteria and viruses, including those that cause disease.
The classical complement pathway can be initiated by the binding of antigen-antibody complexes to the C1q protein. The globular regions of C1q recognize and bind to the Fc region of antibody isotypes IgG or IgM. [2] These globular regions of C1q can also bind to bacterial and viral surface proteins, apoptotic cells, and acute phase proteins. [5]
In IgG, IgA and IgD antibody isotypes, the Fc region is composed of two identical protein fragments, derived from the second and third constant domains of the antibody's two heavy chains; IgM and IgE Fc regions contain three heavy chain constant domains (C H domains 2–4) in each polypeptide chain.
The levels of surface expression of IgD isotype has been associated with differences in B cell activation status but their role in serum is poorly understood. [6] The IgG, IgE and IgA antibody isotypes are generated following class-switching during germinal centre reaction and provide different effector functions in response to specific antigens.