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  • Immunity

    What is the Immune System?

    Dr Jane Winter
    Written by Dr Jane Winter | Dietitian, Science Communication Manager
    What is the immune system

    We’re hearing a lot about the immune system at the moment, but what exactly is it and how does it work? Here’s a simple explanation of some of the components of immune system.

    What is the immune system? (1)(2)

    The immune system is made up of different organs, cells and chemicals that all play a role in protecting us from harmful microorganisms. Even our skin and gut form part of our immune defence system.

    Some important components of our immune system:

    White blood cells

    White blood cells are “key players” responsible for seeking out microorganisms that are foreign. These cells include lymphocytes and other immune cells.


    Antibodies are important in identifying foreign microorganisms (and toxins that they can produce) and marking them for “destruction” for the immune system to attack. The immune system “reads” the antigens on the surface of the harmful microbe and releases antibodies.

    The Lymphatic system

    The Lymphatic system is a network of vessels, lymph nodes and white blood cells. Its main role is to react to bacteria and interact with cells and cell products that may otherwise lead to disease.

    How does the immune system work? (3)(2)

    The immune system is activated when the body recognises something that is not meant to be there. When this happens, the immune cells attach to the foreign matter and work together to destroy it.

    Once our immune system encounters a microorganism for the first time, it stores information about it and how to fight it. This way, if we come into contact with it again, our immune system will know how to fight it straight away.

    Your immune system is always learning and adapting; therefore, our immunity is its ability to resist and protect us from particular microorganisms.

    This is how vaccines work; they expose your immune system to a small amount of a microorganism (not harmful) so that your body is able to recognise it and fight it quickly if it is exposed to it in the future.

    It’s also important to remember that overall nutrition status, and pattern of food intake (comprised of foods, nutrients and non-nutritive bioactive compounds) impact the functioning of the immune system(5).

    Why do we need an immune system?(4)

    We are continuously exposed to organisms (that we can inhale, swallow, inhabit our skin). Whether or not these can make us unwell, depends on what the microorganism is (and how harmful it is to our body) and the ability of our immune system to act as a defence system.

    How does the gut play a role in immune health?

    The human gut is home to billions of bacteria (known as the gut microbiota) which play a fundamental role in our immune system. The gut microbiota protects against foreign microorganisms. In return, our bodies provide the microbiota with food and nutrients so that a delicate balance is at play(6). Disruption to this balance can be caused by medications such as antibiotics, dietary patterns or disease states(7) but this is still the topic of much scientific research.

    How can we support our immune system?

    • Healthy immune system warriors need good, regular nourishment, make sure that your diet includes these nutrients: zinc, selenium, iron, copper, magnesium, folic acid, and vitamins A, B6, C & D.
    • Your overall nutrition status, state of nourishment, and pattern of food intake (comprised of foods, nutrients and non-nutritive bioactive compounds) impact the functioning of the immune system
    • Take care of your gut health as the gut can be an entry point to pathogens: Gut microbiota work together with the immune system to maintain our health.
    • Keep active: Exercise can support the immune system by reducing inflammation in the body.
    • The stress response is the body’s way to keep safe but stress can also lead to an increased and over reaction to triggers including immune response. It is important to minimize stress to support the natural immune response
    • Getting enough sleep is important. During sleep, your immune system releases proteins called cytokines. Cytokines are necessary when responding to infection or inflammation.


    1. Immune system. (2020). Retrieved 31 March 2020, from
    2. Immune system. (2020). Retrieved 31 March 2020, from
    4. Parkin, J., & Cohen, B. (2001). An overview of the immune system. The Lancet, 357(9270), 1777-1789.
    5. Venter C et al. Nutrients 2020;12(3):818.
    6. Kamada N et al. Nature Rev Immunol 2013;13:321-335
    7. McBurney M et al. J Nutr 2019;149:1882-1895