Describe how the human body produces monoclonal antibodies and explain one way in which they can be used in medicine.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (5 marks)
A specific antigen is injected into an animal, such as a mouse, to trigger an immune response.
Lymphocytes are then taken from the animal; these cells produce antibodies that are complementary to the injected antigen.
The lymphocytes are fused with tumour cells to form hybridoma cells.
Hybridoma cells divide continuously, producing large quantities of identical (monoclonal) antibodies.
One medical use is in diagnostic tests – for example, a monoclonal antibody that binds to a specific molecule present only when a patient is positive for HIV will give a positive result, indicating infection.
Lymphocytes are then taken from the animal; these cells produce antibodies that are complementary to the injected antigen.
The lymphocytes are fused with tumour cells to form hybridoma cells.
Hybridoma cells divide continuously, producing large quantities of identical (monoclonal) antibodies.
One medical use is in diagnostic tests – for example, a monoclonal antibody that binds to a specific molecule present only when a patient is positive for HIV will give a positive result, indicating infection.
Examiner tips
- Use the exact sequence of steps: antigen injection → lymphocyte isolation → fusion with tumour cells → hybridoma production. Mention the term "hybridoma" and that it produces identical antibodies. Give a clear example of a medical use and explain why it works (specific binding).
Common mistakes
- Mixing up the order of steps (e.g. saying hybridoma cells are made before lymphocytes are fused). Failing to mention that the antibodies are identical (monoclonal) or that hybridomas divide continuously. Giving a vague medical use without explaining how the monoclonal antibody functions.
Mark scheme (5 marks)
- A specific antigen is injected into an animal (such as a mouse) to trigger an immune response
- Lymphocytes are taken from the animal; these produce antibodies complementary to the antigen
- Lymphocytes are fused with tumour cells to form hybridoma cells
- Hybridoma cells divide continuously to produce large quantities of identical (monoclonal) antibodies
- Named valid medical use correctly explained — e.g. in diagnostic tests (such as for HIV or Chlamydia) the monoclonal antibody binds to a specific molecule only present when the patient is positive for that disease, indicating a positive result; OR used in cancer treatment where monoclonal antibodies bind to antigens on cancer cells whilst carrying chemotherapy drugs to target them specifically
Key terms in this question
Related
- All WJEC A-Level Biology (Wales) revision notes →
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- Decode the mark scheme abbreviations →
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