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6.5 Making Monoclonal Antibodies

GCSE Biology · AQA · Chapter 6: Preventing and Treating Disease

A free GCSE Biology lesson for AQA (8461) from OBA School: what monoclonal antibodies are and how hybridoma cells are used to make them. 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 what monoclonal antibodies are and why they are specific
  • Describe the steps used to produce monoclonal antibodies
  • Explain why lymphocytes are fused with tumour cells to make hybridomas
  • Calculate cell numbers from repeated division

Key words

  • Antigen: A molecule (usually a protein) that an antibody recognises and binds to.
  • Lymphocyte: A type of white blood cell that makes antibodies.
  • Monoclonal antibody: Identical antibodies made by clones of one hybridoma cell, all binding the same antigen.
  • Tumour cell: A cancer cell that divides rapidly and does not stop dividing.
  • Hybridoma: A cell made by fusing a lymphocyte with a tumour cell.
  • Clone: A genetically identical copy of a cell or organism.

What are monoclonal antibodies?

Antibodies are proteins. Each has binding sites with a shape that is complementary to one antigen, so it is specific. Monoclonal antibodies are produced from a single clone of cells, so they are all identical and are specific to one binding site on one protein antigen. This means they can target a specific chemical or specific cells in the body.

The problem and the solution

Lymphocytes make antibodies, but they do not divide in the lab, so you cannot grow lots of them. Tumour cells divide rapidly and keep dividing, but they do not make the antibody we want. Fusing the two gives a hybridoma cell that has both features: it makes the antibody and divides.

  • Lymphocyte; Makes the wanted antibody? Yes; Divides rapidly? No
  • Tumour (myeloma) cell; Makes the wanted antibody? No; Divides rapidly? Yes
  • Hybridoma; Makes the wanted antibody? Yes; Divides rapidly? Yes

The steps in production

  • Step 1: a mouse is injected with the chosen antigen. Its lymphocytes respond by making antibodies against it.
  • Step 2: lymphocytes making the right antibody are collected from the mouse (usually from its spleen).
  • Step 3: the lymphocytes are combined with a particular kind of tumour cell to make hybridoma cells.
  • Step 4: hybridoma cells divide and make the antibody.
  • Step 5: a single hybridoma cell making the wanted antibody is cloned to produce many identical cells.
  • Step 6: a large amount of the antibody is collected and purified.

Exam tip: Learn the key phrase: “mouse lymphocytes are combined with a particular kind of tumour cell to make a cell called a hybridoma cell”.

Maths skill: growing the clone

Hybridoma cells divide by mitosis. If every cell divides once in a set time, the number of cells doubles. After n divisions, one cell becomes 2ⁿ cells.

Worked example: counting cells

A hybridoma cell divides every 20 hours. How many cells are there after 10 days, starting from one cell?
10 days = 240 hours, so there are 240 ÷ 20 = 12 divisions.
Number of cells = 2¹² = 4096.

Answer: 4096 cells

Common mistakes

  • Saying the mouse is injected with antibodies. It is injected with the antigen.
  • Saying the lymphocyte is fused with “any cell”. It is fused with a tumour cell, because tumour cells divide rapidly.
  • Saying monoclonal antibodies are made by the mouse. They are made by cloned hybridoma cells grown in the lab.
  • Forgetting the cloning step: a single hybridoma cell is cloned so all the antibodies are identical.

Revision questions

Try these, then check your answers below each one.

Question 1. What is injected into a mouse at the start of making monoclonal antibodies? (Choose from: The chosen antigen, Antibodies, Tumour cells, Hybridoma cells.)

Answer: The chosen antigen

Working: The mouse is injected with the antigen so its lymphocytes make the specific antibody.

Question 2. What name is given to the cell made by fusing a lymphocyte with a tumour cell?

Answer: hybridoma

Working: The fused cell is a hybridoma.

Question 3. True or false? Monoclonal antibodies are all identical because they come from clones of a single hybridoma cell.

Answer: True

Working: True. One hybridoma cell is cloned, so every antibody is the same.

Related lessons

Continue in the full course

This lesson is section 6.5 (AGCBH0605) 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.

 

 

 

 

 

 

 

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