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Immune system basics

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Did you know that there are two defence systems protecting you from invading foreign substances? We guide you on a learning journey through your immune system.

What is the role of the immune system?

The immune system is our protector from invading foreign substances, such as bacteria and viruses, which may be detrimental to our health. The cells and chemicals of the immune system are all geared to protect us from the potentially harmful substances our body comes into contact with on a daily basis.

Our immune system is complex; however, it can be broken into two systems of defence that work together: the innate immune system and the adaptive immune system.

The innate immune system

The innate immune system can be thought of as the body’s first port of call when responding to foreign substances. It is known as innate (i.e. native or natural) as we have this arm of the immune system from birth.

It includes parts of our body such as the skin, a natural barrier to external substances, and our mucous membranes, such as those lining the mouth, lungs and nasal passages, which trap foreign substances and expel or destroy them.This is often known as the body’s first line of immune defence, and it is important in stopping pathogens from gaining entry to the body.

The innate immunity also includes other defence mechanisms such as inflammation, fever and phagocytes. (Phagocytes are white blood cells which have the ability to recognise, engulf and destroy foreign objects.) These mechanisms respond to foreign substances if they have breached the first line of defence and entered the body.

The defence mechanisms of innate immunity are unspecific as they do not work to protect the body from specific pathogens (as the adaptive immune system does). Instead, they are a blanket approach to all pathogens.

Your defence mechanisms explained

  • Inflammation – Inflammation is a local response to tissue damage, including infection and is an important part of the innate immune system. It is characterised by swelling, heat, redness and pain.
  • Heat and redness – Due to increased blood flow to the area
  • Swelling – The body increases the flow of blood and lymphatic fluid to the area which brings with it many of the important innate immune system cells such as phagocytes.
  • Pain – This often occurs due to tissue damage and swelling. The pain and swelling can limit function.

The adaptive immune system

The adaptive immune system is just that: adaptive to foreign substances. Unlike the innate immune system, adaptive immunity is specific to pathogens, and the cells of the adaptive immune system are programmed to attack specific foreign substances.

This arm of the immune system, compared to innate immunity, takes much longer to act.

For the adaptive immune system to become attuned to a specific foreign substance, it needs to be exposed to it first. Cells that are involved in adaptive immunity are known as B and T cells and are white blood cells. After initial exposure, cells of the adaptive immune system form a memory of that particular substance, so that next time you are exposed to this substance, your body will mount a stronger response that may prevent illness from occurring.

Working together

The two arms of the immune system do vastly different jobs within the body; however, they are both equally important.  These two systems work hand in hand with one another to protect the body from invading nasties like bacteria and viruses. 

When we are exposed to a foreign pathogen or object, the body will generally respond by activating the immune system.

Keeping your first line of defence (innate immunity) healthy

Vitamin A – Ensure you are getting adequate vitamin A through ensuring you get enough yellow, green and red fruits and vegetables. Cod liver oil is also a good source of vitamin A. Vitamin A is essential for mucous membrane health.

Vitamin C – It is important for supporting the health of our innate immune cells such as phagocytes.

Water – Drink plenty of water so mucous membranes don’t dry out. Dry mucous membranes may be more susceptible to invasion from bacteria and viruses.

References available on request