Apply monoclonal antibodies
Explain how monoclonal antibodies can support disease diagnosis and targeted treatment.
AS Level · Cambridge International Biology 9700, 2028–2030. Written practice is self-checked; human subject-teacher review and supervised practical evidence remain separate.
Before you begin
- Pathogens carry antigens, and specific receptors on lymphocytes can recognise complementary antigen shapes.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Why can a monoclonal antibody be useful in a diagnostic test?
What you will learn
- Explain specific antigen detection in a diagnostic test
- Outline how monoclonal antibodies can be used in treatment
Build the explanation
A monoclonal antibody binds one specific antigen. In diagnosis, a labelled monoclonal antibody can bind a target molecule in a sample; a signal indicates that the target is present. For example, a pregnancy test detects human chorionic gonadotropin (hCG) in urine using antibodies and a visible line system. In treatment, monoclonal antibodies can bind a target on a cell or molecule to block its function, mark a target for immune recognition, or deliver a linked substance to target cells. Their specificity can make targeting possible.
Apply it carefully
The test detects a target; it does not by itself explain the cause, severity or full clinical status. Treatment mechanisms vary by antibody and disease, and not every monoclonal antibody works in the same way. Mention the target and mechanism rather than promising a cure. These are syllabus principles, not treatment recommendations.
Pause and explain
Which hormone is detected in a standard pregnancy test?
Worked example
How can a labelled monoclonal antibody indicate that an antigen is in a sample?
Show the worked solution
- The antibody binds its specific antigen.
- A label produces a detectable signal at the binding location.
Answer If the target antigen is present, the labelled monoclonal antibody binds it and produces a detectable signal.
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Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Outline how monoclonal antibodies can be used to detect a target molecule in a sample.
Give me a hint
Link specific binding with a measurable label.
Compare my reasoning
- The antibody binds a complementary target antigen.
- A label or signal associated with binding reveals the target's presence.
A monoclonal antibody with a binding site complementary to the target is added to the sample. If the target is present, antibody–target binding produces a detectable label or signal, indicating the target is present.
Look for these in your work
- Specific binding stated
- Signal linked to target presence
- Conclusion limited to detection
A positive pregnancy-test line is detected. State what the test identifies and one conclusion it does not establish by itself.
Give me a hint
Name the target and distinguish detection from diagnosis of every condition.
Compare my reasoning
- The test detects hCG in the sample.
- It does not by itself establish a complete assessment of health or pregnancy status beyond the test's validated interpretation.
The test uses antibodies to detect hCG in the sample. The signal alone is not a full clinical assessment and should be interpreted according to the test instructions and appropriate professional context.
Look for these in your work
- hCG named
- Scope of test limited
- No unsupported diagnosis
Give two different principles for therapeutic monoclonal antibodies, without claiming all antibodies share one mechanism.
Give me a hint
One may block a target; another may mark or deliver to a target.
Compare my reasoning
- A monoclonal antibody can block a target molecule or receptor.
- It can also mark a target for immune recognition or carry a linked substance to target cells.
Therapeutic monoclonal antibodies can bind and block a target molecule or receptor, mark a target for immune recognition, or in some designs deliver a linked substance to target cells. The mechanism depends on the antibody and target.
Look for these in your work
- Two mechanisms stated
- Target specificity linked
- Mechanism variation acknowledged
Common mistakes
- Claiming a positive signal gives a complete diagnosis
- Saying all monoclonal antibodies kill target cells directly
- Omitting the target antigen or molecule
What can you explain now?
Why can a monoclonal antibody be useful in a diagnostic test?
Compare with the explanation
It binds a specific target antigen
A label or indicator can reveal target binding.
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Make it stick
How does specific binding support diagnostic detection and targeted treatment?
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