Immune System Report

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This is an essay on the human immune system. It is divided into four topics: microbes, catching a disease, preventing diseases and vaccinations. It will provide to you lots of information on how we live and how easily diseases can spread, which can lead to severe illnesses. So this will teach you more about how to fight them.


There are two different types of microbes: bacteria and viruses.

Bacteria are very small living cells (about 1/100th the size of your body cells.) They can reproduce very rapidly inside your body. They can make you feel ill by damaging your cells and producing toxins. These are the bad effects; some bacteria can be useful in some places e.g. digestive system. Bacteria are cells with no nucleus. The DNA is free in the cytoplasm.

Viruses are much smaller then cells (about 1/100th the size of a bacterium.) they damage your cells, which makes you feel very ill indeed. They replicate themselves by invading the nucleus of a cell and using DNA that it contains to produce many copies of themselves. After this process, the cell then bursts, releasing all the new viruses. In this way they can reproduce very quickly.

Catching a disease

Diseases can form when micro-organisms such as certain bacteria and viruses enter the body.

Three common ways in which diseases can be spread are; being in unhygienic conditions (food with bacteria); being in contact with other infected people (contact with animals) and also diseases can be spread in air pollution. All of these conditions end with bacteria and viruses entering the bloodstream, and start to reproduce. There are also hereditary diseases such as haemophilia which is passes on by parent’s faulty genes.

In flood conditions bacteria and viruses are spread in water. Water formed floods can also effect the water we drink and cook with (although bacteria dies in conditions less then five degrees and in conditions higher than sixty degrees). The water from rivers and streams disperse from their banks and carry their polluted water, which has travelled through muddy areas. The water is not purified and may be drunk by people. They are inserting millions of bacteria and viruses which make us ill. This increases the rate of disease in a town or a city.

Modern city help to prevent diseases due to technology. Our food is stored in Fridges and freezers to prevent bacteria growing on food, our water is purified before we drink it and we have medicines near us to help cure diseases caused by bacteria and viruses. In the olden days people used to get water from sewages, this is why they had a less life span then we do now. All of this insures that you are less likely to catch many diseases in a More Economically Developed Country (MEDC) than a Less Economically Developed Country (LEDC).


Once you catch a disease it releases a lot of harmful micro-organisms in your body, such as bacteria and viruses. As soon as the white blood cells get a sniff of this they begin creating many antibodies. These then travel to all parts of the body to kill the invading cell. Once you have been ill you then become immune to the illness. It is called ‘natural immunity.’ This term means that next time you get the same illness in your body, the antibodies will be waiting ready so you won’t get ill. A vaccination will help build up an immunity to a disease as it injects dead micro-organisms into your bloodstream. This will mean that the white blood cells will act by producing antibodies against the micro-organisms even though they are dead, so when a live micro-organism attacks, the antibodies are more than ready to fight back!

A few examples of types of diseases which can be vaccinated against are: whopping cough, tuberculosis (T.B), polio, meningitis and measles mumps rubella-(known as the MMR vaccine)


From this essay we have learnt a lot of new things. We have learnt how we catch and prevent diseases, so in the future we can stop them. We have also learnt exactly what viruses and bacteria do to your body. The most interesting fact we found was that you can never catch the same disease again, as your body becomes immune to it; this even involves a simple cold. We enjoyed and found this essay fascinating.

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