Monoclonal Antibody . Monoclonal antibodies (Mab, from the English phrase with the same meaning as in Spanish: monoclonal antibody) are identical antibodies because they are produced by a single type of cell in the immune system , that is, all clones come from a single mother cell. It is possible to produce monoclonal antibodies that bind specifically to any molecule with an antigenic character. This phenomenon is very useful in biochemistry , molecular biology , and medicine .
Discovery
The researchers Niels K. Jerne , Köhler and Cesar Milstein described the technique that allowed the cultivation of hybridomas or hybrid cells of B lymphocytes with tumor plasma cells of multiple myeloma. With this fusion of two cells, one programmed to produce a specific antibody but which does not multiply indefinitely (lymphocyte) and another immortal with a great capacity for growth but which does not produce immunoglobulin (myeloma cell), the genetic information necessary for the synthesis of the desired antibody and a capacity for protein synthesis are combined, allowing its indefinite multiplication both in vitro and in vivo. For this contribution to science Jerne, Kölher and Milstein received the Nobel Prize in Medicine in 1984. In 2010 , monoclonal antibodies have been around 30 years since their invention, ceasing to be a biological curiosity to become a very important form of treatment and diagnosis in various diseases. There are more than 17 FDA-approved monoclonal antibodies, but the number of monoclonal antibodies in clinical trials is high, representing 30 percent of all compounds under investigation in 2005. Very important for the treatment of various diseases such as rheumatoid arthritis, various cancers, Crohn’s disease …
Production
If a foreign substance (antigen) is injected into the body of a mouse or human, some of the B cells in its immune system will turn into plasma cells and begin producing antibodies that bind to that antigen. Each B cell produces only one type of antibody, but different B cells will produce structurally different antibodies that bind to different parts of the antigen. This natural physiological mixture of antibodies is known as ‘polyclonal antibodies’. To produce monoclonal antibodies, B cells are first taken from the spleen of an animal that has been exposed to the antigen. These B cells are fused in the presence of PEG ( polyethylene glycol ) with multiple myeloma tumor cells (a type of cancer ) that can be grown indefinitely in cell culture. This fusion makes the cell membranes more permeable. These fused hybrid cells, called hybridomas, can multiply rapidly and indefinitely, since they are tumor cells after all and can produce large amounts of antibodies. Hybridomas are sufficiently diluted and cultured to obtain a different number of certain colonies, which produce only one type of antibody. Antibodies from different colonies are tested for their ability to bind to a certain antigen, for example with a type of test called ELISA , and to be selected and isolated in the most effective way.
The technology required for the production of antibodies in the absence of immunization of the animal is known. This is the so-called recombinant antibody technology. Advances in gene technology have greatly facilitated the genetic manipulation, production, identification and conjugation of recombinant antibody fragments, obtaining new multivalent and multispecific antibodies. These technologies have made it possible to develop strategies for screening monoclonal antibodies outside the human body. To do this, it is necessary to have, first of all, enormous libraries of antibody genes, usually by PCR amplification of lymphocyte cDNA, or, alternatively, by in vitro gene synthesis using randomized wobble primers. The screening method of these libraries must have an efficiency comparable to that of the immune system, which can be achieved by exposing the produced antibodies on the surface of microorganisms. Examples of the microorganisms used are filamentous phages such as M13 or bacteria. This surface presentation allows a physical link to be established between the antigen-binding function and the antibody gene, such that the affinity to the antigen allows the microorganism carrying the antibody gene of interest to be isolated from among millions of others. Once the specific clone is isolated, it is amplified for the production of the antibody of interest, for example in E. coli.
Applications
Once monoclonal antibodies that bind to certain substances have been produced, they can be used to detect the presence and quantity of that substance, using a Western blot test , which detects a substance in a solution, or an immunofluorescence test, which detects a substance in a whole cell. Monoclonal antibodies are also used to purify a substance using techniques called immunoprecipitation and chromatography .
Advantages over polyclonal antibodies
- Greater homogeneity.
- Reproducibility of its effects, as a consequence of its homogeneity.
- Greater potential capacity to select the best antibodies in affinity, type of recognition.
Monoclonal antibodies are used in many fields such as:
- Biomedical research, such as gene identification and cloning, protein identification and isolation, enzyme activation, knowledge of molecular structure and morphogenesis.
- Diagnosis: In medicine, thanks to the high specificity and practically unlimited capacity of monoclonal antibodies to recognize any chemical structure, it allows the detection of hormones, vitamins, cytokines; drug monitoring, detection of infectious diseases in microbiology; detection of allergens in allergy, hematology, tumor markers and myocardial infarctions, forensic applications, immunoscintigraphy. In diagnostic techniques, various molecular biology tools are used such as ELISA, EIA , cytometry, immunohistochemistry, immunofluorescence. Monoclonal antibodies are some of the most used substances in diagnostic laboratories.
- Catalysis: Monoclonal antibodies have been used as catalysts for multiple chemical reactions.
- Biosensors: Monoclonal antibodies coupled to electronic transducers can detect both organic and inorganic molecules such as heavy metal contamination in food and water, detection of toxic gases, etc. A biosensor is an analytical instrument consisting of an immobilized biological material such as an enzyme, antibody, whole cell, organelle or combinations thereof, in close contact with a suitable transducer system that converts the biochemical signal into a quantifiable electrical signal.
- Treatment: Therapeutic applications are the most important field of monoclonal antibodies, as they are capable of eradicating certain infections and destroying cells, including tumor cells, through different mechanisms. For this reason, they are excellent substances for the treatment of infectious diseases, autoimmune diseases, cancer or in transplants to prevent rejection. There are several monoclonal antibodies approved for use in certain diseases.