Antibodies are proteins made by the immune system as part of its defence against
foreign bodies or invading microbes that go into our body. Usually, one type of antibody
molecule will attach itself to only one type of foreign material. When an antigen, after
entering the body, the immune system responds by generating large amounts of the
corresponding antibody.
Generally speaking, the amount of
antibodies produced by the body is adequate for its needs. But by extracting more pure
antibodies from a functioning system, their potentials can be further exploited in
new ways. Monoclonal antibodies are immunoglobulin
molecules derived from a single clone of B lymphocytes which can be grown in large
quantities outside the body. This technique is devised at the University of Cambridge in
the 70s.
In principle, the technique relies
on repeatedly immunizing an animal with the antigen complementary to the required
antibody. The cells responsible for the production is found in the spleen. These cells can
be removed and cultured, but they do not survive long. The key to this lies in fusing
these cells with others able to grow and divide indefinitely and produce in a type of
tumor called a myeloma. The resulting cells will grow and
proliferate indefinitely, as well as making a vast quantity of the antibody. If this
system is suitably adapted, it can be used to produce any type of human antibody.
An application of this is when these
antibodies are attached to drug molecules and injected into the bloodstream, antibodies
specific for tumor cells will concentrate the drug at the
site of the tumor, so minimizing the remote side-effects. These antibodies can also be
used to inactivate undesirable materials. There is growing evidence that a chemical
messenger, known as tumor necrosis factor, is involved in leading to and maintaining the inflammation in joints afflicted with rheumatoid arthritis. The injection of
antibodies offer the possibility of new therapies for this.
This technique is also used in
prenatal testing for fetal abnormalities. A small number of fetal cells
cross the placenta and enter the mother's bloodstream, so it should be possible to detect
abnormalities of the fetus by testing those cells. Using techniques that increase the
amount of genetic material in a cell, it is likely to test for defective genes in a sample containing no more than a
dozen cells. By making monoclonal antibodies specific to fetal cells, we don't need to
worry about catching the one in 5 million fetal cell in the bloodstream. We can join the
antibodies to microscopic beads with a metal core. When added to a blood sample, the
antibody-coated beads will attach themselves exclusively to the few fetal cells that are
present. They are then separated from the maternal cells with a magnet.
Further Readings:
Monoclonal Antibody
Technology - The Basics
New
Developments in Monoclonal Antibodies Are Hopeful
Method of making monoclonal antibodies