What is Immunity? Facts and functions of the immune system

What is the immune system?

It is common knowledge that a strong immune system offers protection against viruses and diseases, while a weak one makes you more susceptible to catching a cold or worse. But what exactly is it and how does it work? Let’s take an in-depth look at immunity!

The definition of immunity

Simply put, immunity is your body’s ability to protect your body from bacteria, viruses, fungi and toxins. Think of it as a protection system. If it wasn’t for our immune system, microorganisms could attack or infect your body at will. Thanks to immunity, that’s not the case.

Different types of immunity

Your immune system consists broadly of three levels of defence. The innate immune system which you are born with and an adaptive immune system that evolves with exposure to microorganisms and the chemicals they release.

Your innate immune system consists of-

  • The physical barrier offered by the skin and mucous membranes
  • Protection offered by the immune system cells (defense cells) and proteins

Your adaptive immune system, also called “acquired immunity” changes with exposure to microorganisms. The adaptive immune system protects us based on its past “experience”. This is why, after being infected with something and getting better, we are no longer (at least for some time) susceptible to the same infection.

The purpose and functions of the immune system

The main function of the immune system is to protect you from harmful microorganisms that may cause infections. However, it doesn’t stop at prevention – if you do get sick, it is your immune system that is your body’s first line of defence. It will fight the infection and act to minimize the damage done to your body. A healthy immune system will be able to fight off most infections. A weakened immune system means illness can last longer, and symptoms may be more severe.

How to bolster your immune system

A healthy lifestyle is the best immune booster. It’s always a good idea to ensure you look after your immune system on a daily basis. Below you will find a few tips on how to keep your immune system healthy and strong through everyday activities.1 Remember that if you think your immunity might be weakened, you should always consult your doctor.

  • Eat a balanced diet, including lots of fresh fruit and vegetables. A healthy diet will provide essential vitamins and minerals your immune system needs to function properly.
  • If you are not sure you are getting enough vitamins and minerals in your diet, consider adding a supplement like Berocca Immune Daily Defence that can help strengthen your immune system.2
  • Get regular exercise.3 This will help reduce stress, which negatively affects immunity, and improve blood circulation, allowing white blood cells to reach any cells affected by disease.
  • Take steps to reduce stress. If you find you are under persistent stress, you can try meditation techniques or yoga.
  • Get quality sleep. Rest allows your body to regenerate and helps your immune system to work adequately.
  • Maintain a healthy weight. People who are overweight have weakened immune function, which can make them more at risk of catching illnesses.4
  • Get proactive to avoid infection. Wash your hands thoroughly and regularly, avoid sharing personal items if sharing space with an infected person and make sure any meat you eat is properly cooked.
  • Don’t smoke. Smoking tobacco is harmful to your immune system and can make it less effective at fighting diseases.
  • Limit alcohol consumption. Alcohol can damage your immune response.


  1. How to prevent infections. Harvard Medical School, 2016. (Accessed 10/02/2020, at https://www.health.harvard.edu/staying-healthy/how-to-prevent-infections.)
  2. Gombart AF, Pierre A, Maggini S. A Review of Micronutrients and the Immune System-Working in Harmony to Reduce the Risk of Infection. Nutrients 2020;12.
  3. Nieman DC, Wentz LM, The Compelling Link Between Physical Activity and the Body’s Defense System, Journal of Sport and Health Science, vol 8, issue 3, May 2019, p 201-217
  4. Andersen CJ, Murphy KE, Fernandez ML, Impact of Obesity and Metabolic Syndrome on Immunity, ADVANCES IN NUTRITION, Volume 7, Issue 1, January 2016, Pages 66–75, https://doi.org/10.3945/an.115.010207
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