Monoclonal antibodies and production of monoclonal antibodies
- Antibodies that arise from a single clone of cells (e.g., myeloma) are homogenous and are called monoclonal antibodies.
- For example, in multiple myeloma, antibodies are produced by a single clone of plasma cells against a single antigenic determinant, and hence antibodies are monoclonal.
- The monoclonal antibodies differ from polyclonal antibodies, which are heterologous and are formed by several different clones of plasma cells in response to antigen.
Method of production of monoclonal antibodies:
- Kohler and Milstein (1975) were the first to describe a method for production of monoclonal antibodies against a desired antigen for which they were awarded Nobel Prize in 1984.
- Monoclonal antibodies are produced by fusion of myeloma cells with antibody-producing cells, resulting in production of hybridomas.
- Hybridomas produce virtually unlimited quantities of antibodies that are useful in research and diagnostics.
- In this procedure, mouse splenic lymphocytes are first fused with mouse myeloma cells to produce hybrid cells or hybridomas.
- Myeloma cell provides the hybrid cell immortality, whereas splenic plasma cell provides the antibody- producing capacity.
- These hybridomas can be maintained indefinitely in culture and continue to produce monoclonal antibodies.
Hybridoma cells are prepared in following ways:
- First, an animal (e.g., mouse) is immunized with the antigen of interest.
- Spleen cells (lymphocytes) are then fused with mouse myeloma cells and grown in culture, which are deficient in the enzyme hypoxanthine phosphoribosyl transferase (HPRT).
- Fusion of the cells is facilitated by addition of certain chemicals, such as polyethylene glycol.
- The fused cells are grown in a special culture medium HAT (hypoxanthine-aminopterin-thymidine medium) that supports the growth of the fused hybrid cells but not of the parent cells.
- Finally, the resulting clones of cells are screened for the production of antibody to the antigen of interest.
- These clones are then selected for continuous cultivation.
- The hybridomas can be maintained indefinitely and will continue to produce monoclonal antibodies.
- Human monoclonal antibodies, such as chimeric antibodies, have been produced with modification of the original technique for therapeutic use, since mouse monoclonal antibodies are not suitable.
- The chimeric antibodies consisting of human constant regions and mouse variable regions are being prepared for use in treatment of leukemia.
- Chimeric antibodies are also used to kill tumor cells either by delivering toxins, such as diphtheria to tumor cells, or by killing tumor cells through complement-mediated cytotoxicity.