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  • What’s going on inside us when we get sick? What do germs have to do with us getting sick? How does our body help us to get better? How does it fight infection?

    This resource provides explanations of the key terms encountered when exploring fighting infection. These are terms that should be emphasised to help give every student a good understanding of the context.

    Cell (human)

    A cell is the smallest basic unit that you are made up of, yet each cell contains all the genetic information necessary to make a human being. (All living organisms are made up of cells.)


    The invasion and multiplication of microorganisms in body tissues.

    Immunisation and vaccination

    Immunisation is the process of becoming immune to disease. Vaccination is the process of being vaccinated with a vaccine and becoming immune to a disease.


    The study of the immune system.

    Immune cells

    The cells belonging to the immune system. They are special cells that have specific functions. They work together to eliminate pathogenic microorganisms that might enter your body. These amazing cells can change shape so they can work their way from the bloodstream and squeeze through tissue to reach the site of an infection.

    Immune response

    The way the immune system reacts when pathogenic microorganisms get into the body.

    Immune system

    A system of cells, tissues and organs that work together to protect the body.

    Lymph system

    The structure that allows the immune cells to move around and protect the body from harmful invaders. It is the tissues and organs of the immune system. The lymph system is a system of thin tubes (vessels) that run throughout the body. The vessels contain lymph fluid. The white blood (immune) cells are found within this fluid. Lymph nodes are small round masses of tissues found in different places in the body – the main places being the neck, underarm and groin. The lymph nodes are ‘home’ to many of the immune cells.

    Pathogenic microorganism

    A microorganism is generally a living organism that is so tiny it can only be seen with the aid of a microscope. Most of them are harmless, and some are helpful to us. Pathogens cause disease. Pathogenic microorganisms are tiny organisms that can cause disease. Examples of these are bacteria, fungi and protozoa. Sometimes viruses are referred to as microorganisms even though they are not living organisms. They can be pathogenic, however.


    A substance that improves immunity to a particular disease. The vaccine stimulates the body’s immune system so that it can more easily recognise and destroy a particular microorganism that it might later encounter.

      Published 7 April 2016 Referencing Hub articles
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