An antibody (Ab), also known as an immunoglobulin (Ig), is a large Y-shaped protein produced by B-cells that is used by the immune system to identify and neutralize foreign objects such as bacteria and viruses. The antibody recognizes a unique part of the foreign target, called an antigen. Each tip of the "Y" of an antibody contains a paratope (a structure analogous to a lock) that is specific for one particular epitope (similarly analogous to a key) 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 its target directly (for example, by blocking a part of a microbe that is essential for its invasion and survival). The production of antibodies is the main function of the humoral immune system.

Antibodies are secreted by a type of white blood cell called a plasma cell. Antibodies can occur in two physical forms, a soluble form that is secreted from the cell, and a membrane-bound form that is attached to the surface of a B cell and is referred to as the B cell receptor (BCR). The BCR is only found on the surface of B cells and facilitates the activation of these cells and their subsequent differentiation into either antibody factories called plasma cells, or memory B cells that will survive in the body and remember that same antigen so the B cells can respond faster upon future exposure. In most cases, interaction of the B cell with a T helper cell is necessary to produce full activation of the B cell and, therefore, antibody generation following antigen binding. Soluble antibodies are released into the blood and tissue fluids, as well as many secretions to continue to survey for invading microorganisms.

Antibodies are glycoproteins belonging to the immunoglobulin superfamily; the terms antibody and immunoglobulin are often used interchangeably. Antibodies are typically made of basic structural units—each with two large heavy chains and two small light chains. There are several different types of antibody heavy chains, and several different kinds of antibodies, which are grouped into different isotypes based on which heavy chain they possess. Five different antibody isotypes are known in mammals, which perform different roles, and help direct the appropriate immune response for each different type of foreign object they encounter.

Though the general structure of all antibodies is very similar, a small region at the tip of the protein is extremely variable, allowing millions of antibodies with slightly different tip structures, or antigen binding sites, to exist. This region is known as the hypervariable region. Each of these variants can bind to a different antigen. This enormous diversity of antibodies allows the immune system to recognize an equally wide variety of antigens. The large and diverse population of antibodies is generated by random combinations of a set of gene segments that encode different antigen binding sites (or paratopes), followed by random mutations in this area of the antibody gene, which create further diversity. Antibody genes also re-organize in a process called class switching that changes the base of the heavy chain to another, creating a different isotype of the antibody that retains the antigen specific variable region. This allows a single antibody to be used by several different parts of the immune system.

Read more about Antibody:  Forms, Isotypes, Structure, Function, Immunoglobulin Diversity, Research Applications, Structure Prediction, History

Other articles related to "antibody":

Antibody - History
... See also History of immunology The first use of the term "antibody" occurred in a text by Paul Ehrlich ... The term Antikörper (the German word for antibody) appears in the conclusion of his article "Experimental Studies on Immunity", published in October 1891, which ... was not accepted immediately and several other terms for antibody were proposed these included Immunkörper, Amboceptor, Zwischenkörper, substance sensibilisatrice, copula, Desmon, philocytase ...
Band Of Parents - Projects
... Hu3F8 - The organization's first project was the development of a humanized monoclonal antibody, Hu3F8 ... receive therapy using a murine (mouse derived) monoclonal antibody, 3F8 ... Because the antibody also binds to peripheral nerve cells treatments are painful but are generally without long term complications ...
Antibody Solutions - History
... Antibody Solutions was founded in 1995 by John Kenney and Dennis Gould ... Kenney had managed the monoclonal antibody (McAb) development laboratory for Syntex Research and Gould managed the McAb production facility for Syva Diagnostics ... for Antibody Solutions ...
Multiplex (assay) - Example Multiplex Assay Techniques - Protein-based Multiplex Techniques
... for measuring protein-protein interactions or small molecule binding Antibody microarray a type of protein array in which antibodies are arrayed Phage display for screening large protein libraries for ... multiple HLA antibody identification or reactivity prediction against a panel of organ donor population) Luminex/XMAP principle based muliplexing is done for Anti-HLA antibody ... Biomolecules (such as an oligo or antibody) can be conjugated to the surface of beads to capture analytes of interest ...
Complement Component 4
... remains covalently attached to endothelium for little more than a week and easily detectable by antibody staining ... Detection of C4d is regarded as an indirect sign, a ‘footprint’ of an antibody response ... and inflamed kidney, such as active lupus nephritis, antineutrophil cytoplasmic antibody (ANCA) disease, or anti-glomerular basement membrane (GBM) disease, its ...