An epitope is the part of a macromolecule that is recognized by the immune system, specifically by antibodies, B cells, or cytotoxic T cells. Although usually epitopes are thought to be derived from nonself proteins, sequences derived from the host that can be recognized are also classified as epitopes. A macromolecule is a large molecule with a large molecular mass, but generally the use of the term is restricted to polymers and molecules which structurally include polymers. ... The immune system protects the body from infection by pathogenic organisms. ... Schematic of antibody binding to an antigen An antibody or immunoglobulin is a large Y-shaped protein used by the immune system to identify and neutralize foreign objects like bacteria and viruses. ... B cells are lymphocytes that play a large role in the humoral immune response (as opposed to the cell-mediated immune response). ... A cytotoxic (or TC) T cell is a T cell (a type of white blood cell) which has on its surface antigen receptors called T-cell receptors (TCRs) that can bind to fragments of antigens displayed by the Class I MHC molecules of virus (or other intracellular pathogen) infected somatic...

Most epitopes recognized by antibodies or B cells can be thought of as three-dimensional surface features of an antigen molecule; these features fit precisely and thus bind to antibodies. The part of an antibody that recognizes the epitope is called a paratope. Exceptions are linear epitopes, which are determined by the amino acid sequence (the primary structure) rather than by the tertiary structure of a protein. An antigen is a substance that stimulates an immune response, especially the production of antibodies. ... A linear epitope is an epitope that is recognised by antibodies by its linear sequence of amino acids, or primary structure. ... The general structure of an α-amino acid molecule, with the amine group on the left and the carboxyl group on the right. ... A protein primary structure is a chain of amino acids. ... In biochemistry, the tertiary structure of a protein is its overall shape. ...

T cell epitopes are presented on the surface of an antigen-presenting cell, where they are bound to MHC molecules. T cell epitopes presented by MHC class I molecules are typically peptides between 8 and 11 amino acid in lengths, while MHC class II molecules present longer peptides, and non-classical MHC molecules also present non-peptidic epitopes such as glycolipids. An antigen-presenting cell (APC) is a cell that displays foreign antigen complexed with MHC on its surface. ... MHC I (1hsa) vs MHC II (1dlh) (more details. ...

Epitopes can be mapped using protein microarrays, and with the ELISPOT or ELISA techniques. To meet Wikipedias quality standards, this article or section may require cleanup. ... ELISPOT is an immunological assay based on ELISA (Enzyme-Linked Immunosorbent Assay). ... A 96-well microtiter plate such as the one shown above might be used for ELISA. The Enzyme-Linked ImmunoSorbent Assay, or ELISA, is a biochemical technique used mainly in immunology to detect the presence of an antibody or an antigen in a sample. ...

Genetic sequences coding for epitopes that are recognised by common antibodies can be fused to genes, thus aiding further molecular characterization of the gene product. Common epitopes used for this purpose are c-myc, HA, FLAG, V5.

Interestingly, epitopes are sometimes cross-reactive. This property is exploited by the immune system in regulation by Anti-idiotypic antibodies (originally proposed by Nobel laureate Niels Kaj Jerne). If an antibody binds to an antigen's epitope, the paratope could become the epitope for another antibody that will then bind to it. If this second antibody is of IgM class, its binding can upregulate the immune response; if the second antibody is of IgG class, its binding can downregulate the immune response. Niels Kaj Jerne (December 23, 1911 - October 7, 1994) was a British-Danish-Swedish (English-born) immunologist. ...

Intensive research is currently taking place to design reliable tools that will predict epitopes on proteins.

Epitope was also the name of a publicly traded biotech / medical diagnostics company that existed in the 1980s and 1990s. It was eventually taken over, the name changed to OraSure Technologies and relocated from Oregon to Pennsylvania.

External links

• - History of Epitope, Inc.

Epitope databases

• MHCBN: A database of MHC/TAP binder and T-cell epitopes
• Bcipep: A database of B-cell epitopes
• SYFPEITHI - First online database of T cell epitopes
• IEDB - Database of T and B cell epitopes with annotation of recognition context - NIH funded
• ANTIJEN - T and B cell epitope database at the Jenner institute, UK
• IMGT/3Dstructure-DB - Three-dimensional structures of B and T cell epitopes with annotation of IG and TR - IMGT, Montpellier, France