Therapeutic antibodies are primarily produced using a technique involving hybridoma technology, which merges antibody-producing B cells with immortal myeloma cells.
The Hybridoma Method: A Detailed Explanation
The hybridoma method is the most common way to produce monoclonal antibodies, including therapeutic antibodies. Here's a step-by-step breakdown:
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Immunization: An animal (typically a mouse) is immunized with the target antigen (the molecule the antibody needs to bind to). This triggers an immune response, leading to the production of B cells that create antibodies specific to that antigen.
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B Cell Retrieval: After sufficient antibody production, B cells are harvested from the animal's spleen. These B cells are capable of producing the desired antibodies, but they have a limited lifespan.
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Fusion with Myeloma Cells: The B cells are then fused with myeloma cells. Myeloma cells are cancerous plasma cells that can divide indefinitely in culture, making them "immortal." This fusion is typically achieved using a chemical agent like polyethylene glycol (PEG).
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Selection and Cloning: The resulting fused cells, called hybridomas, possess the antibody-producing capability of the B cell and the immortality of the myeloma cell. However, not all cells will fuse successfully. A selection medium (often HAT medium, containing hypoxanthine, aminopterin, and thymidine) is used to kill unfused myeloma cells and B cells. Only hybridomas can survive in this medium.
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Screening for Antibody Specificity: The surviving hybridomas are then screened to identify those that produce antibodies with the desired specificity and affinity for the target antigen. This involves testing the antibodies produced by each hybridoma against the target antigen.
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Monoclonal Antibody Production: Once a hybridoma cell line producing the desired antibody is identified, it is cloned to create a stable cell line that produces a large quantity of monoclonal antibodies. These antibodies are all identical and bind to the same epitope (specific site) on the target antigen. Production can occur in vitro (cell culture) or in vivo (ascites fluid in animals).
A Summary of the Hybridoma Process
| Step | Description |
|---|---|
| Immunization | Animal injected with target antigen to stimulate B cell production. |
| B Cell Harvest | Antibody-producing B cells are collected from the animal's spleen. |
| Fusion | B cells are fused with myeloma cells to create hybridomas. |
| Selection | Unfused cells are eliminated using a selective medium (e.g., HAT medium). |
| Screening | Hybridomas are screened to identify those producing the desired antibody. |
| Cloning & Production | Selected hybridomas are cloned and cultured to produce large quantities of monoclonal antibodies. |
Alternative Methods
While hybridoma technology is the most common method, other techniques for therapeutic antibody production exist, including:
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Phage Display: A combinatorial library of antibody fragments is displayed on the surface of bacteriophages (viruses that infect bacteria). These phages are then screened against the target antigen to identify those that bind with high affinity.
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Recombinant DNA Technology: Genes encoding the antibody are cloned and expressed in various host cells (e.g., bacteria, yeast, mammalian cells) to produce the antibody. This allows for the production of fully human antibodies or humanized antibodies.
Conclusion
Therapeutic antibodies are predominantly produced through the hybridoma technique, which combines the antibody-producing capabilities of B cells with the immortality of myeloma cells. This process allows for the large-scale production of monoclonal antibodies with specific targeting capabilities.
