Detection Schemes for Antigen-Antibody Reactions

Immunochemical assays are based on the fact that the mammalian immune system forms protein molecules, which bind with high affinity to an antigen molecule. All kinds of molecules can be antigen molecules, and the specificity of these proteins, called antibodies, is rather high. When an animal is injected (immunized) with an antigen, the resulting immune response leads to the generation of a variety of antibody molecules against the antigen, a serum. The composition of the serum depends on the history of the animal. Therefore it is not always easy to reproduce the exact antibody mixture of a serum in different immunizations. These antibody mixtures are very specific, because they recognize a number of different sites or epitopes on the antigen molecule. Each of these antibody molecules is made by one B-cell type. These B-cells can be isolated and grown. A colony which is generated from a single B-cell creates one kind of antibody molecule, a monoclonal antibody. Monoclonal antibodies bind or recognize one epitope on an antigen molecule. As a consequence, monoclonal antibodies bind to any molecule which shows this epitope or molecular geometry. Once a B-cell culture is established, monoclonal antibodies can be reproduced in large quantities.