Infectious Diseases - Immunity

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  • Infectious Diseases: Immunity
  • White blood cells / response to infection
  • Immune memory
  • Vaccination
  • Monoclonal antibodies
  • Quiz

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Immune memory

When your body is first infected with a pathogen, the main task of the immune system is to combat the infection and produce antibodies against the pathogen. However, it also produces memory lymphocytes that remain in your body for many years and remember the pathogen in case it returns. This is called your immune memory and is the reason why you can only catch infections like Chickenpox once. If you get infected a second time, your immune system is already prepared for the pathogen and can quickly make enough antibodies to kill the infection before any symptoms are felt. Vaccination takes advantage of this feature of the immune system.

The first exposure to a pathogen gives only a slow and small immune response. Repeated exposure to the same pathogen gives a much stronger and quicker memory response.

The first exposure to a pathogen gives only a slow and small immune response.
Repeated exposure to the same pathogen gives a much stronger and quicker memory response.

The graph above shows how the levels of antibodies in the blood build up slowly when you are first exposed to a particular pathogen. It takes over 5 days for the antibodies to reach a level that will fight off the infection. During this time, you will feel the symptoms of the infection and damage will be caused to your body tissues. In serious diseases, this can be fatal.

After you have recovered, your immune system retains a number of memory lymphocytes. These can react quickly if you are exposed to the same antigen in the future. If the same pathogen infects you again, more antibodies are produced in a shorter amount of time. The antibodies quickly reach the level that will protect you and when this happens, you may not even feel any symptoms of the illness. This is called the memory response.

Medicine that acts against bacterial infections. Penicillin is an example of an antibiotic.
Protein that is produced by lymphocytes (white blood cells) and that attaches to a specific antigen.
Molecule on the surface of a pathogen that identifies it as a foreign invader to the immune system.
Single-celled organism. Has a cell wall, cell membrane, cytoplasm. Its DNA is loosely-coiled in the cytoplasm and there is no distinct nucleus.
The use of biological organisms or enzymes to create, break down or transform a material
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
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.
Infection caused by the human immune deficiency virus (HIV). It attacks and destroys the immune system.
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.
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.
A type of white blood cell that make antibodies to fight off infections.
A type of white blood cell that consumes dead pathogens that have been killed by antibodies.
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.
A micro-organism that causes disease.
Phagocytes are the white blood cells that protect the body by ingesting harmful foreign particles, bacteria, and dead or dying cells.
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 are one-celled animals
A spore is a reproductive structure that is adapted for dispersal and surviving for extended periods of time in unfavourable conditions.
A poisonous or toxic substance - produced by pathogens.
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.
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.
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 stands for human chorionic gonadotrophin it is a hormone produced by the developing embryo.