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GCSE Biology Revision

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GCSE Biology revision

Uses of monoclonal antibodies

Monoclonal antibodies (biology only) (HT only)

AQA 4.1.1.1
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Identify and describe What Are Monoclonal Antibodies?, Pregnancy Testing: How It Works and Interpreting Pregnancy Test Results in the context of uses of monoclonal antibodies.

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Explain the relationships between What Are Monoclonal Antibodies?, Pregnancy Testing: How It Works and Interpreting Pregnancy Test Results and how they contribute to uses of monoclonal antibodies.

SOME 🎯🎯🎯

Apply and analyse knowledge of What Are Monoclonal Antibodies?, Pregnancy Testing: How It Works and Interpreting Pregnancy Test Results to interpret unfamiliar information about uses of monoclonal antibodies.

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What Are Monoclonal Antibodies?

  • Monoclonal antibodies are identical antibodies produced from a single clone of cells, each specific to one particular antigen.
  • They can be used for pregnancy testing, research, laboratory testing, and treating diseases.
  • A key feature is their specificity — each monoclonal antibody will only bind to one complementary antigen.

Pregnancy Testing: How It Works

  • Pregnancy tests use monoclonal antibodies to detect human chorionic gonadotropin (HCG), a hormone only present in the urine of pregnant women.
  • The test strip contains free monoclonal antibodies (attached to a dye enzyme) that bind to HCG if it is present in the urine.
  • The HCG–antibody complex moves along the strip and binds to fixed antibodies at the test site, triggering a colour change.
  • At the control site, any remaining free antibody (not bound to HCG) binds to fixed antibodies, also producing a colour change to confirm the test is working.

Interpreting Pregnancy Test Results

  • A positive result (pregnant) shows two colour bands — one at the test site and one at the control site — because HCG is present in the urine.
  • A negative result (not pregnant) shows only one colour band at the control site, as there is no HCG to form a complex with the free antibody.
  • The control site is essential because it confirms the test has functioned correctly regardless of the result.

ELISA Tests: Investigating Blood

  • Enzyme-Linked Immunosorbent Assay (ELISA) tests use monoclonal antibodies to detect specific antigens or antibodies in patient blood samples.
  • In an ELISA, an antigen is immobilised on a plate, test serum is added, and any complementary antibodies present will bind to the antigen.
  • A secondary antibody labelled with an enzyme is then added; after washing away unbound antibody, a substrate is added to produce a colour change if binding has occurred.
  • ELISAs can be used to measure hormone levels in the blood or to detect the presence of specific pathogens.

Using Monoclonal Antibodies to Treat Cancer

  • Cancer cells often display specific proteins on their surface called tumour markers, which can be targeted by specially designed monoclonal antibodies.
  • Anti-cancer drugs can be attached to monoclonal antibodies so that the drug is delivered directly to the cancer cell, reducing damage to healthy tissue.
  • Radioactive material can be attached to monoclonal antibodies to locate the position of a tumour during a scan.
  • A chemical can be attached to the monoclonal antibody and delivered to the cancer cell to inhibit its growth or kill it.
  • Monoclonal antibodies can also attract immune cells to the cancer site, helping the immune system launch an attack against the tumour.

How Monoclonal Antibodies Target Cancer Cells

  • The monoclonal antibody is designed to be complementary to a specific tumour marker antigen found on the surface of cancer cells.
  • Once injected into the patient, the antibody travels through the body and binds specifically to the tumour marker, delivering its payload directly to the cancer site.
  • This targeted approach means healthy cells are largely unaffected, making it a more precise treatment compared to conventional therapies.

Side Effects of Monoclonal Antibodies

  • Patients can develop allergic reactions to monoclonal antibodies, as with any drug.
  • Monoclonal antibodies have been linked to deaths in some patients with conditions such as multiple sclerosis.
  • Antigens can change over time due to gene mutations, meaning a monoclonal antibody may no longer recognise its target antigen, rendering it ineffective.
  • The production of monoclonal antibodies involves the use of mice, raising concerns about animal rights and welfare.

Advantages of Monoclonal Antibodies

  • Monoclonal antibodies can be used to treat a wide range of diseases, making them highly versatile in medicine.
  • As a cancer treatment, monoclonal antibodies generally cause fewer side effects than alternative therapies such as chemotherapy.
  • They enable rapid diagnosis of conditions such as pregnancy and infectious diseases through quick colour-change reactions.
  • Their high specificity means they target only the intended antigen, reducing the risk of unintended effects on other cells or tissues.