4.3.2.1Producing monoclonal antibodiesHigher tier
Biology only, and Higher tier only — monoclonal antibodies are outside Combined Science and outside the Foundation paper
Monoclonal antibodies are produced from a single clone of cells. The antibodies are specific to one binding site on one protein antigen, and so are able to target a specific chemical or specific cells in the body.
That specificity is the whole reason they are useful. An ordinary drug goes everywhere in the body; a monoclonal antibody goes to one thing and nowhere else.
The production sequence is a favourite exam question, and it has to be given in order:
1. Mouse lymphocytes are stimulated to make a particular antibody. 2. The lymphocytes are combined with a particular kind of tumour cell, making a cell called a hybridoma cell. 3. The hybridoma cell can both divide and make the antibody — the lymphocyte contributes the antibody, the tumour cell contributes the ability to divide endlessly. 4. Single hybridoma cells are cloned to produce many identical cells, all producing the same antibody. 5. A large amount of the antibody is collected and purified.
- Monoclonal antibody
- An antibody produced from a single clone of cells, specific to one binding site on one protein antigen.
- Hybridoma cell
- A cell made by combining a lymphocyte with a tumour cell, which can both divide and make the antibody.
Common mistake
The tumour cell is not there to cause cancer or to make antibodies. It is there for one property only: it divides indefinitely. The lymphocyte supplies the antibody and cannot keep dividing; the tumour cell can divide and makes nothing useful. Fusing them gets both.
4.3.2.2Uses of monoclonal antibodiesHigher tier
You are not expected to recall any specific test or treatment. What you are expected to do is explain how one works when you are given the information — which always comes back to the same sentence: the antibody binds to one specific antigen, so whatever is attached to the antibody goes only where that antigen is.
Monoclonal antibodies create more side effects than expected, and they are not yet as widely used as everyone hoped when they were first developed. An evaluation question wants the advantages and the disadvantages, and then a judgement.
Advantages: they target one type of cell, so healthy cells are damaged far less than by conventional chemotherapy; they can be produced against almost any antigen; and they made accurate, cheap diagnostic tests possible.
Disadvantages: they cause more side effects than predicted, and they are expensive and difficult to attach to drugs.
There are ethical issues to consider alongside the science. Production begins by stimulating mouse lymphocytes and fusing them with tumour cells, so animals are used and some people object to that. The cost also decides who gets treated: a therapy that works but is unaffordable in most of the world raises a question about fairness that the biology alone does not answer.
Before you practise
- Monoclonal antibodies come from a single clone of cells and bind to one binding site on one antigen.
- Lymphocyte + tumour cell = hybridoma: one supplies the antibody, the other supplies endless division.
- Clone the hybridoma, then collect and purify the antibody.
- Uses: diagnosis, measuring blood levels and detecting pathogens, research with fluorescent dyes, and targeted treatment of cancer.
- You are given the specific test in the question — explain it from the specificity, do not memorise it.
- More side effects than expected, so not yet as widely used as hoped.