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April 7, 2020

How does our immune system work?

Every day our bodies have the difficult task of selecting what has to be rejected as foreign material to prevent illnesses, including viral illnesses such as COVID-19.

This sorting process is carried out by our immune system by our scavenging cells. These are cells that can attack, devour and digest bacteria, foreign particles, and other cells.

Every day our bodies will scavenge hundreds of unwanted particles and cells. These will be abnormal cells arising from a multitude of sources including the DNA in our cells being hit by pollutants, allergens and other agents, and viral infections.

Our immune system recognises unwanted foreign cells by detecting the proteins present on the surface of cells. Viruses, bacteria, and other foreign cells are recognised as being different from natural healthy cells, and this is when the immune system usually responds and attacks these unhealthy cells.

What role do white blood cells play in the immune system?

Our bodies naturally have many white cells, somewhere between 4000 and 11000 per microlitre of healthy blood. There are six main types of white blood cells but one type in particular, lymphocytes play an important role in our natural immune system defences.

Some of these white cells are known as natural ‘killer cells’ because they destroy infected or cancerous and virally infected cells in our body. Their actions are often suppressed in conditions of abnormal immunity such as viral infections, including the coronavirus.

In normal circumstances we can test to measure the impact of viruses and other agents impact on the immune system, but it’s not always possible. It’s very early in the science of COVID-19 to understand how it is working on the body’s natural immune defence system.

How does the immune system cope with allergies and viruses?

Allergen – substances that cause the body to react, e.g. airborne particles such as pollen, air pollution, and spores from indoor moulds

Allergy – the reaction between the allergen and the antibodies

Antigen – a protein usually not found naturally in the body that stimulates an immune response in the body

Antibody – a protein manufactured by white blood cells to neutralise antigens in the body

What’s the difference between and allergy and a virus?

Allergies and viral infections often share very similar symptoms such as coughing, sneezing, and a runny nose. Whereas allergies are caused by unwanted allergens entering the body such as pollen, common illnesses such as colds are caused when viral infections make their way into the body.

Viruses are microscopic cells surrounded by a protective coat of protein that can only multiply inside the living cells of another organism. What we’re witnessing with the coronavirus pandemic is a virus which acts on the body in as yet, unknown ways. The symptoms reported range from mild to deadly.

What happens when the immune system is overwhelmed?

The difficulty that we all face is that when these cells are not disposed of, they can multiply, and because they are so similar to our own normal cells in any tissue, the aberrant cells can develop and multiply unrestricted.

What is viral load?

It is quite simply the amount of virus inside any individual. Viral load is measured by calculating how much volume of the virus is present in either blood or plasma.

It is not yet understood how viral load is involved in the development of the symptoms of COVID-19 but speculation in the scientific community is building around the theory that a significantly higher viral load present the body could be related to the severity of the illness some people are experiencing.

Early research reported in The Lancet* further suggests that the viral load of COVID-19 is at its highest at the beginning of the disease, which could explain why it appears to travel between people so rapidly.

In our next article we will share information about how we can strengthen our immune systems, and what nutrients we need to sustain our health and wellbeing.


Written in conjunction with experts at Breakspear Medical Group Ltd

*The Lancet article

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