Monoclonal Antibodies - Uses and Immunity

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How are monoclonal antibodies produced?

* Antibodies are produced by B-lymphocytes (a type of white blood cell).

* Monoclonal antibodies are produced from clones of a single white blood cell

(This means all of the antibodies are identical and will only target one specific

protein antigen)

* However, lymphocytes don’t divide very easily so it is difficult to grow more of

them.

* Tumour cells, on the other hand, don’t make antibodies but divide lots – so can

be grown easily.

* It is therefore possible to fuse a mouse B-lymphocyte with a tumour cell to

create a cell called a hybridoma. The hybridoma cell can divide and make the

antibody.

* Hybridoma cells can be cloned to get lots of identical cells. These cloned cells all

produce the same antibodies (monoclonal antibodies).

* A large amount of the antibody can be collected and purified.

* 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. You can make

monoclonal antibodies that bind to anything you want e.g. an antigen that’s

only found on the surface of one type of cell

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How can monoclonal antibodies be used?

* For diagnosis such as in pregnancy tests

* in laboratories to measure the levels of hormones and other chemicals in blood,

or to detect pathogens

* in research to locate or identify specific molecules in a cell or tissue by binding

to them with a fluorescent dye

* to treat some diseases: for cancer the monoclonal antibody can be bound to a

radioactive substance, a toxic drug or a chemical which stops cells growing and

dividing. It delivers the substance to the cancer cells without harming other cells

in the body.

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How are monoclonal antibodies used in pregnancy tests?

* A hormone called HCG is found in the urine of pregnant women

* Pregnancy testing sticks detect this hormone. This is how they work:

* The bit of the stick you wee on has some antibodies to the HCG hormone with

blue beads attached.

* The test strip (which turns blue if you are pregnant) has some more antibodies

to the hormone stuck on to it, so they can’t move.

* The HCG hormone binds to the antibodies on the bit of the stick where you wee

and the antibodies on the test strip.

If you’re pregnant and you wee on the stick:

* The HCG hormone binds to the antibodies attached to the blue beads.

* The urine moves up the stick carrying the HCG hormone and the blue beads

with it.

* The blue beads and HCG hormone bind to the antibodies on the test strip –

so the antibodies get stuck on the test strip turning it blue – showing you

are pregnant.

If you’re not pregnant and you wee on the stick:

* The urine still moves up the stick carrying the blue beads. * But because there is no HCG hormone to bind to the antibodies on the test strip it doesn’t go blue.

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How are monoclonal antibodies used to treat diseases?

* Different cells in the body have different antigens on their surface – so you can

make monoclonal antibodies that will bind to specific cells in the body.

* Cancer cells have antigens on their cell membrane that are not found on normal

body cells – they’re called tumour markers.

* In labs you can make monoclonal antibodies that will bind to these tumour

markers.

* An anti-cancer drug can be attached to these monoclonal antibodies. This might

be a radioactive substance, a toxic drug or a chemical which stops cancer cells

growing and dividing.

* The antibodies are given to a patient through a drip.

* The antibodies target specific cells (the cancer cells) because they only bind to

the tumour markers.

* The drug kills the cancer cells but doesn’t kill any normal body cells near the

tumour

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Cancer

* Cancer is the result of changes in cells that leads to uncontrolled growth and

division.

* Benign tumours are growths of abnormal cells which are contained in one area,

usually within a membrane. They do not invade other parts of the body.

* Malignant tumour cells are cancers. They invade neighbouring tissues and spread

to different parts of the body in the blood where they form secondary tumours.

* Scientists have identified lifestyle risk factors for various types of cancer e.g.

smoking and lung cancer, obesity and cancers of the bowel, liver and kidney. U.V.

radiation from the sun can also cause skin cancer.

* Viral infections can also be a risk factors for certain cancers e.g. HPV and cervical

cancer.

* There are also genetic risk factors for some cancers e.g. having certain faulty

genes has shown an increased likelihood of developing breast and ovarian

cancer.

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Natural Immunity

* If your white blood cells have made a particular antibody in the past they can

remember how to make that particular antibody.

* If you have an illness caused by a particular pathogen your white blood cells

produce the correct antibody and destroy the pathogen.

* If you are infected by exactly the same identical pathogen your white blood cells

will remember how to make the correct antibody, produce it quickly and

destroy the pathogen before it can make you ill.

* If the pathogen is different it will have different antigens on its surface and your

white blood cells will need to make a different antibody to destroy it. – You can

become ill while you are waiting for your white blood cells to make the correct

antibody