An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of the pathogen, called an antigen. Each tip of the "Y" of an antibody contains a paratope that is specific for one particular epitope on an antigen, allowing these two structures to bind together with precision. Using this binding mechanism, an antibody can tag a microbe or an infected cell for attack by other parts of the immune system, or can neutralize it directly.
Immunoglobulin D (IgD) is an antibody isotype that makes up about 1% of proteins in the plasma membranes of immature B-lymphocytes where it is usually co-expressed with another cell surface antibody called IgM. IgD is also produced in a secreted form that is found in very small amounts in blood serum, representing 0.25% of immunoglobulins in serum. The relative molecular mass and half-life of secreted IgD is 185 kDa and 2.8 days, respectively. Secreted IgD is produced as a monomeric antibody with two heavy chains of the delta (δ) class, and two Ig light chains.
Immunoglobulin M (IgM) is one of several isotypes of antibody that are produced by vertebrates. IgM is the largest antibody, and it is the first antibody to appear in the response to initial exposure to an antigen. that's why it is also called acute phase antibody.In humans and other mammals that have been studied, plasmablasts residing in the spleen are the main source of specific IgM production.
The immunoglobulin heavy chain (IgH) is the large polypeptide subunit of an antibody (immunoglobulin). In human genome, the IgH gene loci are on chromosome 14.
V(D)J recombination is the mechanism of somatic recombination that occurs only in developing lymphocytes during the early stages of T and B cell maturation. It results in the highly diverse repertoire of antibodies/immunoglobulins and T cell receptors (TCRs) found in B cells and T cells, respectively. The process is a defining feature of the adaptive immune system.
Allelic exclusion is a process by which only one allele of a gene is expressed while the other allele is silenced. This phenomenon is most notable for playing a role in the development of B lymphocytes, where allelic exclusion allows for each mature B lymphocyte to express only one type of immunoglobulin. This subsequently results in each B lymphocyte being able to recognize only one antigen. This is significant as the co-expression of both alleles in B lymphocytes is associated with autoimmunity and the production of autoantibodies.
DNA repair protein XRCC4 also known as X-ray repair cross-complementing protein 4 or XRCC4 is a protein that in humans is encoded by the XRCC4 gene. In addition to humans, the XRCC4 protein is also expressed in many other metazoans, fungi and in plants. The X-ray repair cross-complementing protein 4 is one of several core proteins involved in the non-homologous end joining (NHEJ) pathway to repair DNA double strand breaks (DSBs).
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. During this process, the constant-region portion of the antibody heavy chain is changed, but the variable region of the heavy chain stays the same. Since the variable region does not change, class switching does not affect antigen specificity. Instead, the antibody retains affinity for the same antigens, but can interact with different effector molecules.
The immunoglobulin light chain is the small polypeptide subunit of an antibody (immunoglobulin).
Protein L was first isolated from the surface of bacterial species Peptostreptococcus magnus and was found to bind immunoglobulins through L chain interaction, from which the name was suggested. It consists of 719 amino acid residues. The molecular weight of Protein L purified from the cell walls of Peptostreptoccus magnus was first estimated as 95kD by SDS-PAGE in the presence of reducing agent 2-mercaptoethanol, while the molecular weight was determined to 76kD by gel chromotography in the presence of 6 M guanidine HCl. Protein L does not contain any interchain disulfide loops, nor does it consist of disulfide-linked subunits. It is an acidic molecule with a pI of 4.0. Unlike Protein A and Protein G, which bind to the Fc region of immunoglobulins (antibodies), Protein L binds antibodies through light chain interactions. Since no part of the heavy chain is involved in the binding interaction, Protein L binds a wider range of antibody classes than Protein A or G. Protein L binds to representatives of all antibody classes, including IgG, IgM, IgA, IgE and IgD. Single chain variable fragments (scFv) and Fab fragments also bind to Protein L.
Immunoglobulin lambda-like polypeptide 1 is a protein that in humans is encoded by the IGLL1 gene. IGLL1 has also recently been designated CD179B.
Ig mu chain C region is a protein that in humans is encoded by the IGHM gene.
Immunoglobulin heavy locus, also known as IGH, is a region on human chromosome 14 that contains a gene for the heavy chains of human antibodies.
Immunoglobulin lambda locus, also known as IGL@, is a region on the q arm of human chromosome 22, region 11.22 (22q11.22) that contains genes for the lambda light chains of antibodies.
Ig heavy chain V-III region VH26 is a protein that in humans is encoded by the IGHV@ gene.
Recombination signal sequences are conserved sequences of noncoding DNA that are recognized by the RAG1/RAG2 enzyme complex during V(D)J recombination in immature B cells and T cells. Recombination signal sequences guide the enzyme complex to the V, D, and J gene segments that will undergo recombination during the formation of the heavy and light-chain variable regions in T-cell receptors and immunoglobulin molecules.
Somatic hypermutation is a cellular mechanism by which the immune system adapts to the new foreign elements that confront it, as seen during class switching. A major component of the process of affinity maturation, SHM diversifies B cell receptors used to recognize foreign elements (antigens) and allows the immune system to adapt its response to new threats during the lifetime of an organism. Somatic hypermutation involves a programmed process of mutation affecting the variable regions of immunoglobulin genes. Unlike germline mutation, SHM affects only an organism's individual immune cells, and the mutations are not transmitted to the organism's offspring. Because this mechanism is merely selective and not precisely targeted, somatic hypermutation has been strongly implicated in the development of B-cell lymphomas and many other cancers.
An R-loop is a three-stranded nucleic acid structure, composed of a DNA:RNA hybrid and the associated non-template single-stranded DNA. R-loops may be formed in a variety of circumstances, and may be tolerated or cleared by cellular components. The term "R-loop" was given to reflect the similarity of these structures to D-loops; the "R" in this case represents the involvement of an RNA moiety.
The genome of most cells of eukaryotes remains mainly constant during life. However, there are cases of genome being altered in specific cells or in different life cycle stages during development. For example, not every human cell has the same genetic content as red blood cells which are devoid of nucleus. One of the best known groups in respect of changes in somatic genome are ciliates. The process resulting in a variation of somatic genome that differs from germline genome is called somatic genome processing.
Anti-immunoglobulin antibodies are defined as a protein that detects other antibodies from an organism. Specifically, anti-immunoglobulin antibodies are created by B-cells as antibodies to bind to other immunoglobulins. Immunoglobulins have two regions: the constant region and the variable region. The constant region is involved in effector function, while the variable region is involved in recognizing and binding to antigens. Anti-immunoglobulin antibodies may bind to either the variable or constant region of the immunoglobulin. Anti-immunoglobulin antibodies are a type of secondary antibody. They are able to detect primary antibodies through multiple methods such as a Western blot, immunohistochemistry, immunofluorescence staining, flow cytometry, and ELISA.
