Infectious Diseases - Immunity

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Monoclonal antibodies

Vaccines are not the only form of medical treatment which relies on the immune system.

Monoclonal antibodies are antibodies which are made to target particular cells or chemicals in the body. Some lymphocytes (called B lymphocytes) make antibodies but cannot divide. Scientists combine mouse B lymphocytes which have been stimulated to make a particular antibody with a type of tumour cell to make a cell called a hybridoma.

Hybridoma cells can both make a specific antibody and divide. The hybridoma cells are cloned to make a large number of identical cells which all make the same antibodies. The antibodies are collected and purified. These are monoclonal antibodies – antibodies from a single clone of cells

Making monoclonal antibodies

Monoclonal antibodies produced by hybridoma cells can be used in a number of ways

Pregnancy tests rely on monoclonal antibodies which bind to a hormone (HCG) which is made in the early stages of pregnancy. Tiny amounts of the hormone are passed out of the body in the urine. This is what is picked up by the monoclonal antibodies in the pregnancy test.

A positive pregnancy test – they are so sensitive that they can be taken on the first day of a missed period.
© iStock photo.com

Diagnosis of disease – monoclonal antibodies can be made which bind to specific antigens on blood clots or on cancer cells. The monoclonal antibodies can also carry markers which make it easy for doctors to see where they have built up. This allows doctors to detect problems before they seriously affect a person's health. For example, the blood test for prostate cancer uses monoclonal antibodies to bind to prostrate-specific antigens.

Treatment of disease – monoclonal antibodies can be used to carry drugs to specific tissues. Because they bind to the antigens in a tumour, for example, they can be used to take drugs or radioactive substances directly to the cancer cells.

Advantages and disadvantages of monoclonal antibodies in treatment of disease

The potential advantages of using monoclonal antibodies in the treatment of cancer are great because monoclonal antibodies only bind to the specific cancer cells that need treatment. Healthy cells are not affected at all. In contrast conventional drug treatment is carried all around the body in the blood and can have a devastating effect on healthy cells as well as cancer cells. Radiotherapy treatment is targeted on the area of the body affected by the cancer but still usually affects the healthy tissue in the area as well.

However monoclonal antibodies create more side effects than expected. Doctors and scientists thought they would act like a 'magic bullet' affecting only the diseased tissue. It hasn't quite worked out like that and monoclonal antibodies are not yet as widely used or as successful as everyone hoped.

Antibiotic

Medicine that acts against bacterial infections. Penicillin is an example of an antibiotic.

Antibody

Protein that is produced by lymphocytes (white blood cells) and that attaches to a specific antigen.

Antigen

Molecule on the surface of a pathogen that identifies it as a foreign invader to the immune system.

Bacteria

Single-celled organism. Has a cell wall, cell membrane, cytoplasm. Its DNA is loosely-coiled in the cytoplasm and there is no distinct nucleus.

Biotechnology

The use of biological organisms or enzymes to create, break down or transform a material

Dissect

To cut apart, or separate, tissue especially for anatomical study.

Exponential growth

If something is growing exponentially the larger the quantity gets, the faster it grows

Fungus

Micro-organism that can grow in long tubes called hyphae or as single cells. Fungi have a nucleus, cytoplasm and a cell wall.

Herd immunity

If a high percentage of a population is immune to a disease the disease cannot be passed on because it cannot find new hosts.

HIV/AIDS

Infection caused by the human immune deficiency virus (HIV). It attacks and destroys the immune system.

Hybridoma

Hybridoma cells are formed by fusing a specific antibody-producing cell with a type of cancer cell that grows well in tissue culture

Immune system

The body's natural defence mechanism against infectious diseases.

Immunisation

A process which gives immune resistance to a particular disease. The human or animal is exposed to a harmless antigen in order to raise antibodies and provide an immune memory.

Lymphocyte

A type of white blood cell that make antibodies to fight off infections.

Macrophage

A type of white blood cell that consumes dead pathogens that have been killed by antibodies.

Parasite

Organism that feeds off another living host and causes it some damage. An example of a parasite is a tapeworm that lives in the digestive system of a host organism.

Pathogen

A micro-organism that causes disease.

Phagocyte

Phagocytes are the white blood cells that protect the body by ingesting harmful foreign particles, bacteria, and dead or dying cells.

Protein

A polymer made up of amino acids joined by peptide bonds. The amino acids present and the order in which they occur vary from one protein to another.

Protozoa

Protozoa are one-celled animals

Spore

A spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavourable conditions.

Toxin

A poisonous or toxic substance - produced by pathogens.

Vaccination

A small amount of dead or weakened pathogen is introduced into the body. It prepares the immune system to prevent future infections with the live pathogen.

Vaccine

Medicine that contains a dead or weakened pathogen. It stimulates the immune system so that the vaccinated person has an immunity against that particular disease.

Virus

The smallest of living organisms. Viruses are made up of a ball of protein that contains a small amount of the virus DNA. They can only reproduce after they have infected a host cell.

HCG

HCG stands for human chorionic gonadotrophin it is a hormone produced by the developing embryo.