What is the Immune System?

By Monica van de Weerd

The immune system is a busy and intricate network of cells, molecules and lymphatic tissue tasked with the vital role of protection. The cells of the immune system are known as white blood cells (WBCs).

These components can be thought of as our tiny patrol guards, examiners, enforcers, neutralizers and disposers that work together to dutifully protect our body from daily exposure to pathogenic microorganism's and foreign substances.

The root of the word immunity hints to its important function and is derived from the Latin word ‘immunitas’ meaning exemption, which in this instance refers to a body exempt or free from pathogens and disease.

Unlike other body systems which are often confined to specific organs, the immune system works throughout our entire body. It begins from external structures such as our skin, ears, eyes, mouth and digestive tract, right through to our eternal environment which includes body tissues, fluid and blood.

This meticulously designed, complex system has all basis covered when it comes to keeping us protected and in optimal health.  

How does the Immune System work?

The immune mechanisms can be divided into three layers, the first, second and third line of defence. 

First Line Of Defence

To journey into the human body, an opportunistic microorganism or foreign substance will initially come into contact with physical barriers, our skin and mucous membranes. 

These physical barriers are the first line of defense in protecting our internal environment from the external world.

Other first line mechanisms that work to prevent invaders from migrating inwards include bodily fluids and secretions such as mucus to act as a sticky ‘trap’, urine to flush out and eliminate, vomiting to expel toxins or microbes and acidic vaginal secretions which inhibit growth of certain bacteria.

When our external barriers are compromised, for example if we cut our hand, pathogens are able to enter through a metaphorical broken-down door, into the deeper layers of your body's home.

From here, they can further establish, spread and cause injury.

It is at this point, with alarm bells ringing, our second line defenders are activated and rush in to take charge. 

Second Line of Defence

Our second line of defence is called the Innate or Non-Specific Immunity, which are fast acting but have no ‘memory’, meaning their actions are not specifically targeted against one type of foreign invader.

We are born with this innate immunity and it is comprised of WBCs, chemicals and other processes that work rapidly to limit spread and destroy invaders.

The WBCs responsible for quick apprehension of any invaders are phagocytes (neutrophils, monocytes and macrophages) and natural killer cells.

A phagocyte’s job is to engulf and consume invader pathogens and debris, such as damaged or dead cells. Just like pac-man patrols the maze while eating dots, phagocytes are constantly circulating our body on the hunt for old fragments and unwanted microbes.

Natural killer cells, as the name suggests, have the ability to kill a cell, particularly those affected by viruses. Once a natural killer cell spots an abnormality or non-self cell, they then bind to that cell via receptors and release molecules that result in cell death (apoptosis).

Chemical mediators are the support team to WBCs and whose functions are varied. They include inhibiting the growth of microbes, impairing virus replication and enhancing immune, allergic and inflammatory responses.

Third Line of Defence

The Acquired or Specific Immunity is our third line of defence. Acquired Immunity is slower to take effect ranging from several days or even weeks and begins developing from infancy.

Mature WBC’s called lymphocytes are our third line defenders and are able to develop an immunological memory which cleverly remembers the apprehended pathogen. Thus, repeated exposures illicit a more powerful response and builds a specific long-term protective capacity.

Although this final stage of immune response is initially more delayed, unlike the innate mechanisms, adaptive immunity is exceptionally sophisticated and precise when it comes to identifying and eliminating invaders.

An example of Aquired Immunity at play is for the Chickenpox virus, where exposure and infection commonly occurs during childhood, but subsequent exposures during childhood, adolescence and adulthood do not typically result in any unpleasant symptoms.

This immunological memory allows the body to quickly identify dangerous infective agents if they return, and work rapidly to neutralise and destroy. 

The Immune System: Part 2

Taking this knowledge forward, Part 2 of this post will contain all the information you need to know about what weakens the immune system, signs of impaired immune function and what you can do to support this great protecting force in the future. 

SOURCE: IMMUNITY FUEL

Author: Kate Dalliessi, BNHM (Bachelor of Naturopathic and Herbal Medicine)

References
Craft, J., Gordon, C. and Tiziani, A., 2011. Understanding Pathophysiology. Chatswood, NSW: Elsivier Australia.
Hechtman, L., 2019. Clinical Naturopathic Medicine. Chatswood, NSW: Elsevier.
Saladin, K., 2010. Anatomy and Physiology - The Unity of Form and Function. 5th ed. McGraw-Hill College.

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