Antigen

Patent Granted In immunology, an antigen (Ag), or antibody generator, is any substance which provokes an adaptive immune response.[1] An antigen is often foreign or toxic to the body (for example, a bacterium) which, once in the body, attracts and is bound to a respective and specific antibody. That is to say, an antigen is a molecule that also induces an immune response in the body. Each antibody is specifically designed to deal with certain antigens because of variation in the antibody's complementarity determining regions (a common analogy used to describe this is the fit between a lock and a key). Paul Ehrlich coined the term antibody (in German Antikörper) in his side-chain theory at the end of 19th century.[2] The term antigen originally came from ANTIbody GENerator (see section History).