Production of monoclonal antibodies explained
Infection and response • Monoclonal antibodies (biology only) (HT only)
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Definition of monoclonal antibodies
Monoclonal antibodies are identical antibodies produced by many copies of a single cell. The term 'mono' indicates one type and 'clonal' indicates that every antibody molecule comes from the same original antibody‑producing cell. Production of identical antibodies requires cloning of a single hybridoma cell that produces the antibody with a single, unique binding site.
Stimulating lymphocytes to make the antibody
An antigen of interest is injected into a mouse to stimulate its immune system. Lymphocytes in the spleen respond by producing antibodies specific to the injected antigen. Spleen cells are collected because they contain the antibody‑producing B lymphocytes. The immune stimulation step generates cells that produce antibodies matching the antigen’s binding site.
Fusion with myeloma (tumour) cells to form hybridomas
Antibody‑producing spleen cells are fused with myeloma cells (cancerous white blood cells) to form hybridoma cells. Myeloma cells provide the ability to grow indefinitely in culture, while the spleen cells provide the antibody specificity. Fusion produces hybridoma cells that both divide continuously and secrete the desired antibody. Unfused myeloma cells cannot survive in the selective growth medium and die, leaving hybridomas to be cultured.
Cloning and selection of a single hybridoma
A single hybridoma cell that produces the required antibody is isolated and cloned by cell division. Cloning produces a large population of genetically identical hybridoma cells - a single clone - that all secrete the same antibody. Antibodies collected from this culture are therefore identical and specific to one binding site on the antigen. Purification from the culture medium uses methods such as centrifugation, filtration and chromatography.
Molecular basis of specificity
Each antibody molecule has a variable region that forms a binding site complementary to a specific antigen epitope (part of a protein antigen). A single B lymphocyte produces antibodies with one unique variable region; cloning that B cell (via the hybridoma route) preserves that single binding site across all antibody molecules produced. The lock‑and‑key fit between antibody binding site and antigen epitope explains high specificity.
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