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A rabbit hybridoma is a hybrid cell line formed by the fusion of an antibody producing rabbit B cell with a cancerous B-cell (myeloma).
| | This article needs additional citations for verification .(August 2011) |
A rabbit hybridoma is a hybrid cell line formed by the fusion of an antibody producing rabbit B cell with a cancerous B-cell (myeloma).
The rabbit immune system has been documented as a vehicle for developing antibodies with higher affinity and more diverse recognition of many molecules including phospho-peptides, carbohydrates and immunogens that are not otherwise immunogenic in mouse. [1] However, until recently, the type of antibodies available from rabbit had been limited in scope to polyclonal antibodies. Several efforts were made to generate rabbit monoclonal antibodies after the development of mouse hybridoma technology in the 1970s. [2] Research was conducted into mouse-rabbit hetero-hybridomas to make rabbit monoclonal antibodies. [1] [3] However, these hetero-hybridomas were ultimately difficult to clone, and the clones, generally unstable, and did not secrete antibody over a prolonged period of time.
In 1995, Katherine Knight and her colleagues, at Loyola University of Chicago, succeeded in developing a double transgenic rabbit over-expressing the oncogenes v-abl and c-myc under the control of the immunoglobulin heavy and light chain enhancers. The rabbit formed a myeloma-like tumor, allowing the isolation of a plasmacytoma cell line, named 240E-1. Fusion of 240E-1 cells with rabbit lymphocytes produced hybridomas that secreted rabbit monoclonal antibodies in a consistent manner. [4] However, like the early mouse myeloma lines developed in the 1970s, stability was a concern. A number of laboratories which had received the 240E-1 cell line from Dr. Knight’s laboratory reported stability problems with the fusion cell line 240E-1. [5]
In 1996, Weimin Zhu and Robert Pytela, at the University of California San Francisco (UCSF), obtained 240E-1 from Dr. Knight’s laboratory and attempted to develop an improved rabbit hybridoma. [4] Improvements in the characteristics of 240E-1 were accomplished by repeated subcloning, selection for high fusion efficiency, robust growth, and morphological characteristics such as a bright appearance under a phase-contrast microscope. Selected subclones were further tested for their ability to produce a stable hybridoma and monoclonal antibody secretion. After multiple rounds of subcloning and selection processes, a new cell line named 240E-W, was identified and which expressed better fusion efficiency and stability. Cell line 240E-W has since been further developed and optimized for production of rabbit monoclonal antibodies for research and commercial applications.
The process of hybridoma formation in a rabbit first entails obtaining B-cells from a rabbit that has been immunized. There are numerous immunization protocols for rabbit, notably for the generation of polyclonal antibodies. [6] [7] [8] After immunization, B-cells are fused with a candidate rabbit fusion partner cell line to form hybridomas. Resulting antibodies from hybridomas are screened for an antigen which meets criteria of interest by diagnostic tests such as ELISA, western blot, immunohistochemistry, and FACS. The resulting hybrdomas may be subcloned to ensure monoclonal characteristics.
Mitchell Ho and Ira Pastan at National Cancer Institute (Bethesda, USA) isolated a group of rabbit monoclonal antibodies (e.g. YP218, YP223) that recognize rare epitopes of mesothelin, including poorly immunogenic sites close to the C terminal end, for cancer therapy. [9] Dr. Ho's laboratory analyzed the complex structures of rabbit antibodies with their antigens from the Protein Data Bank, and identified antigen-contacting residues on the rabbit Fv within the 6 Angstrom distance to its antigen. [10] They named "HV4" and "LV4", non-complementarity-determining region (CDR) loops that are structurally close to the antigen and located in framework 3 of the rabbit heavy chain and light chain, respectively. Based on computational structural modeling, Ho and Zhang designed a humanization strategy by grafting the combined Kabat/IMGT/Paratome CDRs into a human germline framework sequence. The immunotoxins composed of the humanized rabbit Fvs (e.g. hYP218) fused to a clinically used toxin showed stronger cytotoxicity against tumor cells than the immunotoxins derived from their original rabbit Fvs. The CAR T cells based on the hYP218 antibody also show effective inhibition of tumor growth in mice. [11] The method (i.e. grafting combined Kabat/IMGT/Paratome rabbit CDRs to a stable human germline framework) has been suggested as a general approach to humanizing rabbit antibodies. [10]
In immunology, an antigen (Ag) is a molecule, moiety, foreign particulate matter, or an allergen, such as pollen, that can bind to a specific antibody or T-cell receptor. The presence of antigens in the body may trigger an immune response.
An antibody (Ab) is the secreted form of a B cell receptor; the term immunoglobulin can refer to either the membrane-bound form or the secreted form of the B cell receptor, but they are, broadly speaking, the same protein, and so the terms are often treated as synonymous. Antibodies are large, Y-shaped proteins belonging to the immunoglobulin superfamily which are used by the immune system to identify and neutralize foreign objects such as bacteria and viruses, including those that cause disease. Antibodies can recognize virtually any size antigen with diverse chemical compositions from molecules. Each antibody recognizes one or more specific antigens. This term literally means "antibody generator", as it is the presence of an antigen that drives the formation of an antigen-specific antibody. Each tip of the "Y" of an antibody contains a paratope that specifically binds to one particular epitope on an antigen, allowing the two molecules to bind together with precision. Using this mechanism, antibodies can effectively "tag" a microbe or an infected cell for attack by other parts of the immune system, or can neutralize it directly.
A monoclonal antibody is an antibody produced from a cell lineage made by cloning a unique white blood cell. All subsequent antibodies derived this way trace back to a unique parent cell.
An epitope, also known as antigenic determinant, is the part of an antigen that is recognized by the immune system, specifically by antibodies, B cells, or T cells. The part of an antibody that binds to the epitope is called a paratope. Although epitopes are usually non-self proteins, sequences derived from the host that can be recognized are also epitopes.
Plasma cells, also called plasma B cells or effector B cells, are white blood cells that originate in the lymphoid organs as B cells and secrete large quantities of proteins called antibodies in response to being presented specific substances called antigens. These antibodies are transported from the plasma cells by the blood plasma and the lymphatic system to the site of the target antigen, where they initiate its neutralization or destruction. B cells differentiate into plasma cells that produce antibody molecules closely modeled after the receptors of the precursor B cell.
Immunohistochemistry (IHC) is a form of immunostaining. It involves the process of selectively identifying antigens (proteins) in cells and tissue, by exploiting the principle of antibodies binding specifically to antigens in biological tissues. Albert Hewett Coons, Ernest Berliner, Norman Jones and Hugh J Creech was the first to develop immunofluorescence in 1941. This led to the later development of immunohistochemistry.
Hybridoma technology is a method for producing large numbers of identical antibodies. This process starts by injecting a mouse with an antigen that provokes an immune response. A type of white blood cell, the B cell, produces antibodies that bind to the injected antigen. These antibody producing B-cells are then harvested from the mouse and, in turn, fused with immortal myeloma cancer cells, to produce a hybrid cell line called a hybridoma, which has both the antibody-producing ability of the B-cell and the longevity and reproductivity of the myeloma. The hybridomas can be grown in culture, each culture starting with one viable hybridoma cell, producing cultures each of which consists of genetically identical hybridomas which produce one antibody per culture (monoclonal) rather than mixtures of different antibodies (polyclonal). The myeloma cell line that is used in this process is selected for its ability to grow in tissue culture and for an absence of antibody synthesis. In contrast to polyclonal antibodies, which are mixtures of many different antibody molecules, the monoclonal antibodies produced by each hybridoma line are all chemically identical.
A single-domain antibody (sdAb), also known as a Nanobody, is an antibody fragment consisting of a single monomeric variable antibody domain. Like a whole antibody, it is able to bind selectively to a specific antigen. With a molecular weight of only 12–15 kDa, single-domain antibodies are much smaller than common antibodies which are composed of two heavy protein chains and two light chains, and even smaller than Fab fragments and single-chain variable fragments.
HAT Medium is a selection medium for mammalian cell culture, which relies on the combination of aminopterin, a drug that acts as a powerful folate metabolism inhibitor by inhibiting dihydrofolate reductase, with hypoxanthine and thymidine which are intermediates in DNA synthesis. The trick is that aminopterin blocks DNA de novo synthesis, which is absolutely required for cell division to proceed, but hypoxanthine and thymidine provide cells with the raw material to evade the blockage, provided that they have the right enzymes, which means having functioning copies of the genes that encode them.
Antibody-dependent cellular cytotoxicity (ADCC), also referred to as antibody-dependent cell-mediated cytotoxicity, is a mechanism of cell-mediated immune defense whereby an effector cell of the immune system kills a target cell, whose membrane-surface antigens have been bound by specific antibodies. It is one of the mechanisms through which antibodies, as part of the humoral immune response, can act to limit and contain infection.
Humanized antibodies are antibodies from non-human species whose protein sequences have been modified to increase their similarity to antibody variants produced naturally in humans. The process of "humanization" is usually applied to monoclonal antibodies developed for administration to humans. Humanization can be necessary when the process of developing a specific antibody involves generation in a non-human immune system. The protein sequences of antibodies produced in this way are partially distinct from homologous antibodies occurring naturally in humans, and are therefore potentially immunogenic when administered to human patients. The International Nonproprietary Names of humanized antibodies end in -zumab, as in omalizumab.
Monoclonal antibodies (mAbs) have varied therapeutic uses. It is possible to create a mAb that binds specifically to almost any extracellular target, such as cell surface proteins and cytokines. They can be used to render their target ineffective, to induce a specific cell signal, to cause the immune system to attack specific cells, or to bring a drug to a specific cell type.
Mesothelin, also known as MSLN, is a protein that in humans is encoded by the MSLN gene.
Small modular immunopharmaceuticals, or SMIPs for short, are artificial proteins that are intended for use as pharmaceutical drugs. They are largely built from parts of antibodies (immunoglobulins), and like them have a binding site for antigens that could be used for monoclonal antibody therapy. SMIPs have similar biological half-life and, being smaller than antibodies, are reasoned to have better tissue penetration properties. They were invented by Trubion and are now being developed by Emergent BioSolutions, which acquired Trubion in 2010.
A bispecific monoclonal antibody is an artificial protein that can simultaneously bind to two different types of antigen or two different epitopes on the same antigen. Naturally occurring antibodies typically only target one antigen. BsAbs can be manufactured in several structural formats. BsAbs can be designed to recruit and activate immune cells, to interfere with receptor signaling and inactivate signaling ligands, and to force association of protein complexes. BsAbs have been explored for cancer immunotherapy, drug delivery, and Alzheimer's disease.
Glypican-3 is a protein that, in humans, is encoded by the GPC3 gene. The GPC3 gene is located on human X chromosome (Xq26) where the most common gene encodes a 70-kDa core protein with 580 amino acids. Three variants have been detected that encode alternatively spliced forms termed Isoforms 1 (NP_001158089), Isoform 3 (NP_001158090) and Isoform 4 (NP_001158091).
Monospecific antibodies are antibodies whose specificity to antigens is singular in any of several ways: antibodies that all have affinity for the same antigen; antibodies that are specific to one antigen or one epitope; or antibodies specific to one type of cell or tissue. Monoclonal antibodies are monospecific, but monospecific antibodies may also be produced by other means than producing them from a common germ cell. Regarding antibodies, monospecific and monovalent overlap in meaning; both can indicate specificity to one antigen, one epitope, or one cell type. However, antibodies that are monospecific to a certain tissue, or all monospecific to the same tissue because clones, can be polyvalent in their epitope binding.
Jerrold Schwaber was an American biologist and geneticist. In 1973 he described, with Edward Cohen, a method of producing antibodies involving human–mouse hybrid cells, or hybridomas. They fused "mouse myeloma cells secreting immunoglobulin of known specificity and human peripheral blood lymphocytes not secreting detectable immunoglobulin. The hybrid cells continued secretion of mouse immunoglobulin and initiate synthesis and secretion of human immunoglobulin." The antibody producing cells did not survive long and the antigens that the antibodies targeted remained unknown. In 1975, Georges Köhler, César Milstein, and Niels Kaj Jerne, succeeded in making hybridomas that made antibodies to known antigens and that were immortalized. They shared the Nobel Prize in Physiology or Medicine in 1984 for the discovery. His work in laying the foundation for modern monoclonal antibody technology is recognized.
Recombinant antibodies are antibody fragments produced by using recombinant antibody coding genes. They mostly consist of a heavy and light chain of the variable region of immunoglobulin. Recombinant antibodies have many advantages in both medical and research applications, which make them a popular subject of exploration and new production against specific targets. The most commonly used form is the single chain variable fragment (scFv), which has shown the most promising traits exploitable in human medicine and research. In contrast to monoclonal antibodies produced by hybridoma technology, which may lose the capacity to produce the desired antibody over time or the antibody may undergo unwanted changes, which affect its functionality, recombinant antibodies produced in phage display maintain high standard of specificity and low immunogenicity.
Passive antibody therapy, also called serum therapy, is a subtype of passive immunotherapy that administers antibodies to target and kill pathogens or cancer cells. It is designed to draw support from foreign antibodies that are donated from a person, extracted from animals, or made in the laboratory to elicit an immune response instead of relying on the innate immune system to fight disease. It has a long history from the 18th century for treating infectious diseases and is now a common cancer treatment. The mechanism of actions include: antagonistic and agonistic reaction, complement-dependent cytotoxicity (CDC), and antibody-dependent cellular cytotoxicity (ADCC).
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