The production of monoclonal
You need to have read about
antibodies before studying this section.
How do you make monoclonal antibodies?
As we have seen, antibodies are produced by the type of white
blood cell called B-lymphocytes. It is proving useful to medicine to
produce lots of a specific antibody from multiple clones of a single
white blood cell. The antibodies will be identical and only target one
specific antigen protein molecule. Unfortunately, lymphocyte cells
do not divide easily, but tumour cells can be readily cultured to
undergo rapid cell division, so they are used instead.
The process starts by (i) injecting a mouse with a specific
antigen, this stimulates the production of antibodies against the
antigen and then extracting the B-lymphocytes produced.
Culturing fast dividing tumour cells called myeloma cells.
(iii) You then fuse a mouse B-lymphocyte with a tumour cell to create a
'hybrid' cell called a hybridoma cell - which can be cloned
to make lots of identical cells. It is these cells that produce
identical monoclonal antibodies, which can be collected and
purified for research or direct medical use.
If possible, you can produce monoclonal antibodies that bind to
anything you want e.g. an antigen that is only found on the surface
of a one specific type of cell.
Because monoclonal antibodies only bind to a specific antigen
molecule, you can therefore target a specific cell and destroy it
(e.g. a cancer cell) or 'neutralise' a chemical in the body to
inhibit its poisonous action.
(12b) Uses of monoclonal antibodies
Treating diseases using monoclonal antibody techniques
As we have seen, different cells in the body
have different antigen molecules on their surface, which
gives them a unique molecular signature.
This means you can make monoclonal antibodies
that will bind to ('target') specific cells with that specific
Cancer cells have antigens on their cell
membranes that you do not find on normal healthy body cells and they
are known as tumour markers.
In the laboratory you can culture cells to
produce monoclonal antibodies (see above) that will bind to these
tumour marker antigens, but the real trick is other things you can
do with the monoclonal antibody e.g. diagnose and treat cancer.
anticancer drug-agent can be attached to the monoclonal antibody
- see the diagram below.
The anti-cancer agent might be a toxic drug or
radioactive substance (radioisotope) or any chemical that
growth and division of cancer cells.
Any toxic effect will only
kill the cancer cells, not the healthy non-cancerous cells,
because the anti-cancer agent is only attached to the cancer cell
antibody, which itself, will only attach itself to the cancer
cells - that's the way the antigen-antibody mechanism works.
Advantages and problems with using monoclonal antibodies
to treat disease
Despite the wonderful advantages of
applying monoclonal antibodies to medical treatments, there are
the 'usual' pros and cons.
In other cancer treatments e.g.
chemotherapy and radiotherapy you inadvertently damage
neighbouring healthy cells as well as killing the cancer cells
because of the high energy of the radiation (often gamma
radiation). This doesn't happen with monoclonal antibody drug
cancer treatment where the side effects are much less and healthy cells are not damaged.
Disadvantages: Unfortunately, monoclonal antibodies do
cause more side effects than expected.
Symptoms exhibited include
breathlessness, fever, itchy rashes, head aches, low
blood pressure and nausea and vomiting.
These side effects have limited the
use of monoclonal antibody drug treatments.
Tests for tracing and measuring specific substances
to help in medical diagnosis
e.g. monoclonal antibody applications include
Binding them to a specific hormone
or other molecule in the blood to measure the concentration ('level' of a chemical).
Testing blood samples for the
presence of specific pathogens.
Tracing and locating specific
molecules on cell or tissue.
You first make monoclonal antibodies
that bind to the specific molecule X you are
The monoclonal antibodies are then reacted
bind with a fluorescent dye molecule to facilitate an
If the molecule
X is present in
your analysis sample, the monoclonal antibody will attach
itself to it.
Therefore the presence, location and
concentration of molecule X can be obtained using uv
light to cause a fluorescent effect.
Testing for cancer
You first make the specific antibody
that will bind to the cancer cells, but this antibody is
labelled with a radioisotope.
The radioactive labelled antibody
is fed into the patient through a drip into the bloodstream
and carried all the way around the body.
When the antibody encounters a cancer
cell it will bind to it because it recognises the antigen of
the cancer cell (the tumour marker).
The radiation emitted from the
radioactive tracer is monitored by a special camera (linked
to a computer and screen) and where the cancer cells are
concentrated, the emitted radiation will be the greatest -
this will show up as a bright 'hot spot' on the
Therefore doctors can see exactly
where the cancer is, the size of the tumour and, from
previous scans, whether the cancer is spreading e.g.
secondary cancers from prostate cancer i.e. cancer spreading
out of the prostate gland.
Using monoclonal antibodies to find
Blood clots form when proteins in the
blood join together to form a solid mesh that restricts
You can make monoclonal antibodies,
labelled with a radioactive tracer, that bind to these
After injection of these monoclonal
antibodies into the bloodstream, a special camera (linked to
a computer and screen) can pick out a where the blood clot is
where there is a high concentration of the radioisotope -
shown by a bright 'hot spot' on the screen from the
nuclear radiation emitted by the radioisotope.
Blood clots are very potentially
dangerous and this technique is able to detect them and
allow the doctor to remove them before the patient comes to
Pregnancy testing using monoclonal antibodies
Monoclonal antibodies are used in a pregnancy
test strip/stick which can detect the HCG hormone which is only present
in the urine of pregnant women.
The science behind the test is
illustrated in the diagram below.
You wee onto the end of the strip or dip it into a collected sample
of urine - the method is up to you!
The reaction zone is impregnated with the HCG antibody which has
been modified with an enzyme (e) to facilitate a colour
effect if HCG hormone is present.
As the urine diffuses up the strip this 1st antibody combines with any HCG hormone in the urine and
continues moving along the strip.
In the test zone the HCG combination encounters and attaches itself
to a 2nd, but immobile antibody.
If the HCG hormone is present in the urine
the enzyme triggers a chemical reaction to give a colour change
e.g. the appearance of blue colour would signify a positive
If the HCG hormone is not present, no
colour change is seen, indicating a negative pregnancy result
The control zone is to check that the strip is working correctly,
irrespective of a positive result.
As the urine diffuses further up the strip
it carries along some of the first HCG antibody (with enzyme e) that has not combined with the HCG hormone. It then
encounters an immobile version of the 2nd antibody which already
has the HCG hormone attached to it
If the pregnancy stick is behaving
correctly, you should get the same colour change whether it is a
positive or negative pregnancy test result.
Note: You can impregnate the strip with
different antibodies to test for the presence of other substances in
the urine e.g. the antigens on other pathogens.
Learning objectives for this section on
Be able to describe the formation of monoclonal antibodies using B-lymphocytes
Know what is meant by clones and hybridoma cells.
Be able to describe some medical uses antibody techniques
testing, anticancer drug-agents, their advantages, blood tests, measurement
concentrations, tests for cancer cells.
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