Antibodies, also referred to as immunoglobulins, are glycoproteins naturally produced in response to invading foreign particles antigens such as microorganisms and viruses. Antigens recognized and bound by antibodies can be proteins such as receptors expressed on cancer cells, sugars on bacterial and viral cell surfaces, hormones, chemical compounds, or nucleic acid structures. The region of an antigen that interacts with an antibody is called the epitope.
Each antibody is secreted by a different antibody-producing plasma cell and may be specific for a different epitope. Since the antibodies found in serum are collectively produced by many plasma cells clones , they are described as polyclonal. While this is an advantage for fighting infections in nature, the heterogeneity of polyclonal antibodies limits their use as research tools.
The technique involves removing B cells plasma cell precursors from the spleen of an animal that has been challenged with an antigen, and subsequently fusing with an immortal myeloma tumor cell line. This results in a single-cell hybrid known as a hybridoma. The B cells confer antibody production capability, while the myeloma cells enable hybridomas to divide indefinitely and grow well in culture.
Hybridomas secrete only one antibody type, effectively ensuring a long-term supply of antibodies selective for a single epitope, which are also known as monoclonals. Many of the key structural features of antibodies can be highlighted using immunoglobulin G IgG as a model since IgG is the most abundant antibody in serum.
Figure 1. Schematic Structure of an IgG Molecule. Figure 2. Light and Heavy Chain Structure. Light chains are approximately amino acids in length and can be divided into two equal 'variable' and 'constant' regions. Heavy chains are about amino acids in length and are subdivided into four amino acid segments - one variable region and three constant regions. Advances in the understanding of antibody structure and function, bacteriophage replication, and DNA manipulation and mutagenesis led to the development of a method for the generation of recombinant monoclonal antibodies using phage display antibody libraries.
This technology addresses the limitations of the traditional hybridoma method, which is known to be time consuming and expensive, requiring extensive expertise, as well as specialized cell culture and animal facilities. In addition, antigens used to generate antibodies using hybridoma technology can be toxic in animals, or poorly immunogenic, and thus may not elicit an immune response.
Antibody library and phage display technology can be used to generate highly specific, high affinity antibodies in vitro without reliance on the immunogenicity of the antigen or the use of animals. Such recombinant antibodies are suitable in research applications where traditional monoclonal antibodies are used.
Antibody-producing B cells are produced in the bone marrow and mature in the periphery. During B-cell maturation, the antibody genes immunoglobulin genes undergo recombination, generating an enormous repertoire of antigen-binding sites the variable region.
The gene locus encoding the H chain variable region: The locus contains an array of about V gene segments, about 25 D gene segments, and 6 J gene segments. One each of the V , D , and J gene segments are selected and joined together.
One each of the V and J gene segments are selected and joined together. Immunoglobulins antibodies to countless antigens are produced from a limited number of genes by recombination of gene segments. Gene rearrangements also occur during T cell maturation in the thymus.
Even if some autoreactive B cells evade the elimination process and reach the periphery, those B cells that produce antibodies to self-antigens autoantibodies are inactivated by another mechanism including regulation by Tregs.. Possible causes of autoimmune disease include viral infection, high fever, pregnancy, and the recently proposed abnormalities in the intestinal microbiome.
However, the details of the mechanism remain unknown. Principle and method of the experiment.
The three functions of antibodies. Nest page: Types of antibodies.
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