Monoclonal antibodies

3. Infection and Response

A monoclonal antibody is one single antibody, made over and over again by a clone of identical cells. Because every molecule in the batch is the same, the whole batch binds to one target and nothing else - and that is what makes monoclonal antibodies so useful.

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110 questions2 subtopicsFoundation and Higher

What monoclonal antibodies covers

Every subtopic below has its own questions, mark schemes and notes.

4.3.2.1Producing monoclonal antibodies

4.3.2.2Uses of monoclonal antibodies

Every use comes from the same idea: the antibody binds to one thing and nothing else. Attach a coloured bead and you can see the target; attach a dye and you can find it down a microscope; attach a drug and you can kill it.

Key terms

The definitions examiners expect, in the wording that earns the mark.

Antigen — A molecule, usually a protein, on the surface of a cell that the immune system recognises as foreign.

Antibody — A protein made by B-lymphocytes that binds to one specific antigen.

Monoclonal antibody — An antibody produced from a single clone of identical cells, so every molecule in the batch is the same.

Hybridoma — The cell formed by fusing a B-lymphocyte with a tumour cell; it divides rapidly and produces the antibody.

Clone — A group of genetically identical cells produced from one original cell.

HCG — The hormone found in the urine of a pregnant woman that a pregnancy test detects.

Tumour marker — An antigen on the cell membrane of a cancer cell that is not found on normal body cells.

Fluorescent dye — A dye attached to a monoclonal antibody so that the molecule it binds to can be seen under a microscope.

Diagnosis — Working out what condition or infection a person has, as opposed to treating it.

Where marks get lost

The mistakes that come up again and again in this topic.

Do not say the antibodies are collected from the mouse's blood - the mouse's blood holds many different antibodies, so they would not be monoclonal.
Say what each parent cell contributes: division from the tumour cell, antibody production from the lymphocyte. Marks are often for that pairing.
A single hybridoma is cloned. If you grew all the fused cells together you would get a mixture of antibodies, not a monoclonal one.
Antigen and antibody are easy to swap over. The antigen is the marker; the antibody is what recognises it.
The pregnancy test does not change colour by a chemical reaction. Coloured beads are simply trapped in one place, and that is what you can see.
Be clear which antibodies move and which are fixed. Losing that distinction loses the marks on any 'explain how the stick works' question.
For cancer treatment, name what is attached: a radioactive substance, a toxic drug, or a chemical that stops cells growing and dividing. 'A drug' on its own is usually one mark, not three.
The side-effects point is a comparison. Fewer side effects than chemotherapy, but still more than scientists originally expected - both halves are needed.
Say why the drug misses healthy cells: normal cells do not carry the tumour marker, so the antibody cannot bind to them.

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