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The first correct description of the antigen-antibody reaction was given by Richard J. Goldberg at the University of Wisconsin in 1952. [1] [2] It came to be known as "Goldberg's theory" (of antigen-antibody reaction). [3] There are several types of antibodies and antigens, and each antibody is capable of binding only to a specific antigen.
An immune complex, sometimes called an antigen-antibody complex or antigen-bound antibody, is a molecule formed from the binding of multiple antigens to antibodies. [1] The bound antigen and antibody act as a unitary object, effectively an antigen of its own with a specific epitope. After an antigen-antibody reaction, the immune complexes can ...
Activation of the C1 complex initiates the classical complement pathway. This occurs when C1q binds to antigen-antibody complexes. The antibodies IgM or certain subclasses of IgG complexed with antigens are able to initiate the complement system: a single pentameric IgM can initiate the pathway, while several monomeric IgG molecules are needed. [3]
Antibodies also form complexes by binding to antigen: this is called an antigen-antibody complex or immune complex. Small antigens can cross-link two antibodies, also leading to the formation of antibody dimers, trimers, tetramers, etc. Multivalent antigens (e.g., cells with multiple epitopes) can form larger complexes with antibodies.
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]
The classical pathway is triggered by activation of the C1-complex. The C1-complex is composed of 1 molecule of C1q, 2 molecules of C1r and 2 molecules of C1s, or C1qr 2 s 2. This occurs when C1q binds to IgM or IgG complexed with antigens. A single pentameric IgM can initiate the pathway, while several, ideally six, IgGs are needed.
An antibody is made up of two heavy chains and two light chains. The unique variable region allows an antibody to recognize its matching antigen. [73] A B cell identifies pathogens when antibodies on its surface bind to a specific foreign antigen. [74] This antigen/antibody complex is taken up by the B cell and processed by proteolysis into ...
An illustration that shows how antigens induce the immune system response by interacting with an antibody that matches the molecular structure of an antigen. In immunology, an antigen (Ag) is a molecule, moiety, foreign particulate matter, or an allergen, such as pollen, that can bind to a specific antibody or T-cell receptor. [1]