6.6 Uses of Monoclonal Antibodies

A free GCSE Biology lesson for AQA (8461) from OBA School: diagnosis, pregnancy tests, laboratory and research uses, cancer treatment, and advantages and disadvantages. Watch the video, read the explanation and worked examples, then try the revision questions. You can work through the full lesson, with every video, practice quizzes and printable worksheets with mark schemes, in our free online course.

What you will learn

• Describe how monoclonal antibodies are used in diagnosis and in pregnancy tests
• Explain how they are used to measure chemicals and locate molecules in research
• Describe how they can be used to treat some cancers
• Evaluate the advantages and disadvantages of monoclonal antibodies
• Interpret data from tests that use monoclonal antibodies

Key words

• hCG: A hormone made only during pregnancy; it is found in the urine of pregnant women.
• Diagnosis: Finding out what disease or condition a person has.
• Fluorescent dye: A dye that glows under special light, so it shows where an antibody has bound.
• Targeted therapy: A treatment that acts only on particular cells, such as cancer cells.
• Side effect: An unwanted effect of a medicine.

Pregnancy tests

Pregnancy tests detect the hormone hCG in urine. They use monoclonal antibodies that bind specifically to hCG.

• Zone 1: hCG in the urine binds to mobile antibodies attached to blue beads. They are carried along the strip.
• Zone 2 (test line): fixed antibodies bind the hCG–antibody complexes, so the beads build up and a blue line appears.
• Zone 3 (control line): fixed antibodies bind any spare mobile antibodies (with or without hCG). This line always appears if the test works.

Diagnosis, laboratories and research

• Measuring chemicals: in hospitals and labs, monoclonal antibodies measure the levels of hormones and other chemicals in blood.
• Detecting pathogens: they bind to antigens of a particular pathogen, showing which pathogen is causing an infection.
• Research: antibodies joined to a fluorescent dye bind to a specific molecule, so scientists can see where it is in a cell or tissue.
• Diagnosing disease: e.g. finding blood clots or cancer cells by attaching a dye or marker that collects where the antibody binds.

Treating cancer

Cancer cells have antigens on their surface that normal cells do not have (or have in much smaller amounts). A monoclonal antibody against these antigens can be bound to a radioactive substance, a toxic drug or a chemical that stops cells growing and dividing. The antibody carries the substance to the cancer cells, so normal body cells are not harmed as much. Some antibodies also help the immune system to attack the cancer cells.

Advantages and disadvantages

• Bind only to specific cells, so healthy cells are not harmed; Disadvantages Have caused more side effects than expected (e.g. fever, vomiting, low blood pressure)
• Can treat a wide range of conditions; Disadvantages Expensive to develop and produce
• Tests are quick, cheap per test, and easy to use; Disadvantages Not yet as widely used as scientists first hoped

Worked example: test accuracy

A clinic used a monoclonal antibody test for a bacterium on 500 people. Lab cultures showed 120 really had the bacterium. The test was positive for 114 of these 120.
Percentage of infected people detected = 114 ÷ 120 × 100 = 95%.
Infected people missed = 120 − 114 = 6.

Answer: 95% detected; 6 missed

Common mistakes

• Saying the antibody “kills” cancer cells by itself. Usually it carries a drug, toxin or radioactive substance to them.
• Saying the control line shows the woman is not pregnant. The control line shows the test is working.
• Saying monoclonal antibodies have no side effects. They have caused more side effects than expected.
• Forgetting that antibodies are specific: each binds to one particular antigen.

Revision questions

Try these, then check your answers below each one.

Question 1. Which hormone does a pregnancy test detect?

Answer: hCG

Working: Pregnancy tests detect hCG in urine.

Question 2. A pregnancy test shows a blue control line but no test line. What does this mean? (Choose from: The woman is not pregnant and the test worked, The woman is pregnant, The test has not worked, The woman has a lot of hCG.)

Answer: The woman is not pregnant and the test worked

Working: The control line shows the test works; no test line means no hCG was detected.

Question 3. True or false? Monoclonal antibodies have caused more side effects than scientists expected.

Answer: True

Working: True. This is one reason they are not yet as widely used as was hoped.

Related lessons

• Previous lesson: 6.5 Making Monoclonal Antibodies
• Next lesson: 7.1 Non-Communicable Diseases
• In this chapter: 6.1 Vaccination
• In this chapter: 6.2 Antibiotics and Painkillers
• In this chapter: 6.3 Discovering Drugs

Continue in the full course

This lesson is section 6.6 (AGCBH0606) of our free GCSE Biology course for AQA. In the full course you get every video for this section, a self-marking practice quiz, a printable worksheet with a mark scheme, chapter tests, and your progress saved. Go to the full GCSE Biology course.