Uses of monoclonal antibodies — AQA GCSE Biology
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Uses of monoclonal antibodies explained
Monoclonal antibodies bind to one specific antigen, so they can be used wherever that antigen needs to be detected or targeted.
Read the full explanation
In pregnancy tests, an antibody binds to a hormone (hCG) in urine and produces a visible line. In laboratories, antibodies detect specific molecules in samples, for example in diagnosing infections or identifying blood groups. In medicine, antibodies can carry drugs or radioactive substances to cancer cells, or be used to treat some diseases by binding to specific targets. They may also be used in research to locate substances in cells using fluorescent markers. The uses of monoclonal antibodies are assessed at Higher Tier only.
Some examples include: • for diagnosis such as in pregnancy tests • in laboratories to measure the levels of hormones and other chemicals in blood, or to detect pathogens • in research to locate or identify specific molecules in a cell or tissue by binding to them with a fluorescent dye • to treat some diseases: for cancer the monoclonal antibody can be bound to a radioactive substance, a toxic drug or a chemical which stops cells growing and dividing.
Monoclonal antibodies are identical antibodies produced from a single clone of cells. They bind to one specific antigen, which makes them useful in many ways. In diagnosis, pregnancy tests use monoclonal antibodies that bind to a hormone in urine, producing a visible signal. In laboratories, they measure levels of hormones and other chemicals in blood, or detect pathogens by binding to antigens on microorganisms. In research, they locate or identify specific molecules in a cell or tissue by binding to them with a fluorescent dye, so the target can be seen under a microscope. In treatment, monoclonal antibodies can be bound to a radioactive substance, a toxic drug or a chemical that stops cells growing and dividing; this delivers the agent to cancer cells carrying the target antigen, reducing damage to normal cells.
It delivers the substance to the cancer cells without harming other cells in the body.
A monoclonal antibody is a single type of antibody produced from one clone of cells, so every molecule binds to the same antigen. In cancer treatment the antibody is chosen because its antigen is found on the surface of cancer cells. A substance that kills cells, or a radioactive substance, is attached to the antibody. When the antibody is given to the patient it circulates in the blood and binds only to cells carrying that antigen, so the substance is delivered mainly to the cancer cells. Because healthy cells lack the antigen, they are largely spared, which reduces damage to normal tissue. This is targeted delivery: the antibody acts as a carrier, not as the killer itself.
Students are not expected to recall any specific tests or treatments but given appropriate information they should be able to explain how they work.
This statement sets out how you are assessed on monoclonal antibody uses. You do not need to memorise named tests or named treatments. Instead, a question supplies the information, such as a diagram of an antibody with a substance attached, or a short paragraph about a test strip. You then use that information with your knowledge of antibody specificity to explain the mechanism. For example, if told that a test uses an antibody that binds a particular antigen, you explain that the antibody binds only that antigen, so a colour or line appears only when that antigen is present. The skill is applying the principle of specific binding to unfamiliar material.
Monoclonal antibodies create more side effects than expected. They are not yet as widely used as everyone hoped when they were first developed.
Monoclonal antibodies were expected to become a major way of treating disease because they can be made to bind one specific target. In practice they cause more side effects than were expected. Possible reasons include an immune response to the antibody itself, because it is a protein from another organism, and effects on healthy cells that happen to carry the same antigen. Because of these side effects, and because producing them is demanding, they are not yet as widely used as people hoped when they were first developed. This is a limitation of the technology, not a failure of the underlying idea of specific binding.
Your focus
- Describe at least two uses of monoclonal antibodies.
- Explain how antibody specificity makes these uses possible.
- Distinguish between diagnostic uses and therapeutic uses of monoclonal antibodies.
Show all 15 objectives
- Describe examples of how monoclonal antibodies are used in diagnosis, laboratories, research and treatment.
- Explain how the specificity of a monoclonal antibody allows it to target a particular molecule, cell or pathogen.
- Explain how monoclonal antibodies can deliver a radioactive substance, toxic drug or growth-stopping chemical to cancer cells.
- Describe how a monoclonal antibody carries a substance to cancer cells.
- Explain why healthy cells are largely unaffected by this treatment.
- Use the terms antigen, antibody and targeted delivery correctly in an answer.
- Use information supplied in a question to explain how a monoclonal antibody test or treatment works.
- Link specific antibody binding to an observable result.
- Apply the principle of antibody specificity to an unfamiliar example.
- State that monoclonal antibodies can cause more side effects than expected.
- Give a reason why side effects may occur.
- Explain why monoclonal antibodies are not yet as widely used as was hoped.
Uses of monoclonal antibodies exam tips
Marking Points
- Monoclonal antibodies bind to a specific antigen because their binding sites are complementary to it.
- In pregnancy tests, an antibody binds to a hormone in urine and causes a visible signal.
- In diagnosis, antibodies can detect specific molecules such as pathogens or markers of disease.
- In treatment, antibodies can carry drugs or radioactive substances to specific cells such as cancer cells.
- Monoclonal antibodies are also used in research to locate specific molecules in cells or tissues.
- Monoclonal antibodies bind to one specific antigen, which allows them to target a particular molecule, cell or pathogen.
- In pregnancy tests, monoclonal antibodies bind to a hormone in urine and produce a visible result.
- In laboratories, monoclonal antibodies are used to measure levels of hormones and other chemicals in blood, or to detect pathogens.
- In research, monoclonal antibodies bind to specific molecules in a cell or tissue and are attached to a fluorescent dye so the molecules can be located or identified.
- In cancer treatment, monoclonal antibodies can be bound to a radioactive substance, a toxic drug or a chemical that stops cells growing and dividing.
- The specificity of monoclonal antibodies means the attached substance is delivered mainly to the target cells, which can reduce harm to healthy cells.
- A monoclonal antibody is produced from a single clone of cells and binds to one specific antigen.
- The antigen is present on the surface of the cancer cells, so the antibody binds to them.
- A cell-killing substance or a radioactive substance is attached to the antibody.
- The antibody carries the substance to the cancer cells, so the substance reaches them.
- Healthy cells do not carry the antigen, so they are not targeted and are largely unharmed.
- This is described as targeted delivery, and the antibody itself is the carrier rather than the killing agent.
- You are not required to recall named tests or named treatments for monoclonal antibodies.
- Information about an unfamiliar test or treatment will be given in the question.
- You should use the given information together with the idea that an antibody binds one specific antigen.
- An explanation should link the binding event to the result, such as a colour change or a line appearing.
- Answers should apply the principle to the unfamiliar context rather than recall a memorised example.
- Monoclonal antibodies can cause more side effects than were originally expected.
- A possible cause is an immune response to the antibody, which is a foreign protein.
- Another possible cause is binding to healthy cells that carry the same antigen.
- Because of these problems, monoclonal antibodies are not yet as widely used as was hoped when they were first developed.
- The limitation concerns their use in treatment, while the principle of specific binding remains valid.
Examiner Tips
- 💡Give named examples, such as pregnancy testing or cancer treatment, rather than general statements.
- 💡Always link the use back to the antibody binding to a specific antigen.
- 💡Remember that the uses of monoclonal antibodies are a Higher Tier only topic, so expect questions requiring detailed application of knowledge.
- 💡When giving uses, name the purpose and then state what the monoclonal antibody binds to or carries, for example a fluorescent dye for locating molecules.
- 💡For treatment questions, mention that the monoclonal antibody delivers the radioactive substance, toxic drug or growth-stopping chemical to the target cells.
- 💡Avoid vague answers such as 'they are used in medicine'; specify diagnosis, laboratory measurement, research or treatment.
- 💡Name the antigen as the target and state that it is on the cancer cell surface.
- 💡Use the word targeted and explain that the antibody is the carrier of the substance.
- 💡Link the absence of the antigen on healthy cells to why those cells are largely unharmed.
- 💡Underline the key information in the question before you start writing.
- 💡Use the phrase binds to its specific antigen in your explanation.
- 💡Finish by stating the observable result, such as a colour change or a line appearing.
- 💡Use the phrase more side effects than expected when describing the limitation.
- 💡Give a reason, such as an immune response to the antibody or binding to healthy cells.
- 💡State clearly that they are not yet as widely used as was hoped when first developed.
Common Mistakes
- Saying antibodies kill pathogens directly; correction: they bind to specific antigens, and this binding can be used to detect or target substances.
- Thinking one antibody can be used for any antigen; correction: each monoclonal antibody is specific to one antigen.
- Confusing the role of the antibody with the role of the drug it carries; correction: the antibody targets, while the drug or radioactive substance does the treating.
- Thinking monoclonal antibodies bind to many different antigens: the error is ignoring specificity; the correction is that each monoclonal antibody binds to one specific antigen.
- Confusing diagnosis with treatment: the error is describing a pregnancy test as a treatment; the correction is that pregnancy testing is a diagnostic use, while binding to radioactive or toxic substances is a therapeutic use.
- Believing that the fluorescent dye itself kills cells: the error is mixing up research and treatment uses; the correction is that the dye allows molecules to be located or identified, whereas toxic drugs or growth-stopping chemicals are used to treat disease.
- Saying the antibody directly kills the cancer cells: the antibody delivers an attached substance, and it is that substance which kills the cells.
- Claiming no other cells are affected at all: the intended effect is that healthy cells are largely spared, not that damage is impossible.
- Confusing monoclonal antibodies with antibiotics or with vaccines: monoclonal antibodies are identical antibodies from one clone that bind one antigen.
- Trying to recall a named test or treatment instead of using the information provided: read the passage or diagram and apply the principle of specific binding.
- Describing the antibody as binding generally rather than to one specific antigen: state that the antibody binds only its matching antigen.
- Leaving out the link between binding and the observed result: explain that binding causes the colour change or line to appear.
- Stating that monoclonal antibodies have no side effects: they can cause more side effects than expected, including immune reactions.
- Claiming they are now the main treatment for most diseases: their use is not yet as widespread as was hoped.
- Saying the idea of monoclonal antibodies has been abandoned: the principle still works, but side effects limit how widely they are used.