GCSE · Biology · Edexcel · Spec 1BI0

Uses of monoclonal antibodies

A pregnancy test and a cancer treatment seem to have nothing in common. Both rely on the same trick: an antibody that only ever grabs one thing.

Sort the uses

One antibody, three kinds of job

Pick a use, then put it under the job it does. For each one, ask yourself two things: what does the antibody bind to, and what happens once it has?

Still to sort

Testing and diagnosis (0)

Finds out whether a particular molecule is in a sample, such as whether someone is pregnant or whether a pathogen is present.

Where the line is: The antibodies are stuck to a test strip and the sample (urine, saliva or blood) goes onto them. They are not put into the body.

Locating (0)

Shows WHERE something is: a molecule in cells and tissues, or cancer cells or a blood clot in a patient.

Where the line is: The antibody carries a label, and the label shows up where the target is. It's there to show you the place, not to do damage.

Treating (0)

Carries something to tumour cells that acts on them.

Where the line is: It's the same targeting as locating. The difference is what's attached: a radioactive substance or a toxic drug instead of a label.

6 of 6 still to sort.

Look back at your sorted columns. In every use the antibody does exactly the same thing: it finds its one target and binds to it. The job depends on what happens next.

What 'monoclonal' really means

One kind, lots of copies

A pregnancy test strip is coated with monoclonal antibodies against the hormone HCG.

Which of these is closest to what you think those antibodies are?
How sure are you?

Read the strip

Pregnancy and disease test strips often have two lines, and the two lines do different jobs.

A pregnancy test strip shows only one line: the line that tells you the test has worked. The result line has not changed colour. What does the strip tell you?

Why less damage was expected

?

Reason it through

Why were monoclonal antibody treatments expected to do less harm than traditional cancer treatments?

Link 1 of 4

First link · your turn

Traditional cancer treatments target cells that divide rapidly. Which cells does that include?

2
Locked — reveal the link above first
3
Locked — reveal the link above first
4
Locked — reveal the link above first

Has the promise come true?

Weigh it up

The claim

Monoclonal antibodies are a better cancer treatment than traditional treatments.

Place each piece of evidence to load the balance. Mark the strong ones — they count double.

  1. They deliver a radioactive substance or toxic drug to the tumour cells specifically.

    Evidence 1: does it support or challenge the claim?

  2. They were expected to damage healthy tissue less than treatments that target every rapidly dividing cell.

    Evidence 2: does it support or challenge the claim?

  3. They have caused more side effects than expected, and some of them are serious.

    Evidence 3: does it support or challenge the claim?

  4. The antibodies come from the immune system of another organism, such as a mouse, and some patients' bodies reject them.

    Evidence 4: does it support or challenge the claim?

  5. They are not yet as widely used as was originally hoped.

    Evidence 5: does it support or challenge the claim?

WHAT YOU'VE LEARNED

A quick recap of today's lesson.

One antibody, one target: the same trick behind a pregnancy test, a disease test and a cancer treatment.

What you need to know

  • Monoclonal antibodies are identical antibodies made by the many clones of a single hybridoma cell (a lymphocyte fused with a tumour cell).
  • Each one binds to one specific target, such as an antigen or another biological molecule, because its shape is complementary to it.
  • They are used in testing and diagnosis, in locating molecules, cancer cells and blood clots, and in treating some diseases such as cancer.
  • Monoclonal antibody cancer treatments have not worked as well as first hoped.

The big picture

Monoclonal antibodies are identical antibodies that each bind to one specific target, because their shape is complementary to it. That one property lets them test for molecules such as HCG, diagnose disease by detecting a pathogen's antigen, show where molecules, cancer cells or blood clots are, and carry a radioactive substance or toxic drug to tumour cells. In cancer treatment, though, they have not worked as well as first hoped.

Key points

1Pregnancy tests: the strip carries antibodies specific to HCG. HCG in a pregnant woman's urine binds to them, causing a colour change that shows a positive result.
2Disease tests: antibodies on a strip bind to the antigen of one specific pathogen in saliva or blood, so a positive result shows that pathogen is present.
3Test strips often have two lines. One shows the test has worked and the other shows the result, which helps prevent incorrect results.
4Locating: antibodies labelled with a fluorescent dye show where cells carrying a molecule are. Labelled antibodies injected into the blood show a doctor where cancer cells or a blood clot are.
5Treating cancer: antibodies made against tumour-cell antigens carry a radioactive substance (helps reduce the tumour's size) or a toxic drug (stops tumour cells dividing) to the tumour cells specifically.
6They were expected to cause less damage than traditional treatments, which target all rapidly dividing cells. However, side effects and rejection (the antibodies come from another organism such as a mouse) mean they are not yet as widely used as hoped.

Worked example

Problem

A scientist wants to find out which cells in a tissue sample carry a particular molecule. Explain how monoclonal antibodies could be used to do this.

⚠ Watch out

Mixing up locating cancer and treating it. Both use antibodies that bind to the cancer cells, and the difference is what's attached. A label shows the doctor where the cancer cells are. A radioactive substance or toxic drug acts on the tumour cells.

🧠

Memory hook

Same address, different delivery. The antibody always goes to its one target. The job depends on what happens when it gets there: a colour change (test), a label (locate) or a radioactive substance or toxic drug (treat).

✓

Check yourself

Cover the page. Explain why the same basic idea lets a monoclonal antibody both tell someone they are pregnant and deliver a drug to a tumour.

Flashcards

(13)
What are monoclonal antibodies?
Identical antibodies made by the many clones of a single hybridoma cell.
What is a hybridoma cell?
A lymphocyte fused with a tumour cell.
Why does a monoclonal antibody bind to only one target?
Its shape is complementary to that one target, such as an antigen or another biological molecule.
What are the three main kinds of use for monoclonal antibodies?
Testing and diagnosis, locating things in the body or in cells and tissues, and treating some diseases such as cancer.
Which hormone does a pregnancy test detect, and where is it found?
HCG, which pregnant women produce. It is found in their urine.
What happens on a pregnancy test strip when HCG is present?
HCG binds to the antibodies on the strip, causing a colour change that shows a positive result.
Why do test strips often have two lines?
One line shows the test has worked; the other shows positive or negative. This helps prevent incorrect results.
In a test for a disease, what do the antibodies on the strip bind to?
The antigen of one specific pathogen, in a sample of saliva or blood.
How do monoclonal antibodies help a doctor find cancer cells or a blood clot?
Labelled antibodies are injected, travel in the blood and bind to the target tissue's specific antigens, showing where the problem is.
Why can monoclonal antibodies bind to tumour cells but not other body cells?
Tumour cells can have antigens that healthy body cells don't, and the antibodies are made against those antigens.
What two things can be attached to monoclonal antibodies to treat cancer?
A radioactive substance (helps reduce the tumour's size) or a toxic drug (stops the tumour cells dividing).
Why do traditional cancer treatments often cause hair loss?
They target rapidly dividing cells, and hair follicles divide rapidly too, so they get damaged.
Give two reasons monoclonal antibody cancer treatments haven't worked as well as hoped.
More side effects than expected (some serious), and some patients reject them because they come from another organism, such as a mouse.

Tap any card to flip it, or use Study as deck to go through them one at a time. In the full lesson these run as a spaced-repetition deck — you rate each card Hard, Good or Easy and the tricky ones keep coming back until they stick.

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