The immune system explained simply

How does the immune system work? Can we do something to boost the immune system to make it work better?

The immune system is a complex cooperation between different organs, cells and proteins which together work to recognise, fight off and remember harmful substances in the body.

If you’d like to learn more about how you can take care of your immune system, take a look at our complete guide to immune system and diet.

The immune system is made up of two distinct arms – the innate and the adaptive immune system. The innate system is a quick and heavy-handed response to an issue while the adaptive system is a more targeted response.

The innate system is the first line of defence and can respond with inflammation to a general but non-specific infection or injury. It does not have the long-term memory required for immunity to diseases. This is where the adaptive immune system comes in.

The adaptive immune system includes our white blood cells, of which there are several, but the T- and B-cells are probably best known, plus the antibodies that are created by the white blood cells.

Deals with infections

Your white blood cells cruise around your body and look for trespassers in both blood and tissue - things like harmful bacteria, viruses, parasites and fungi.

The white blood cells have different jobs. The B-cells are the early warning system which recognises foreign substances and organises defense against them. The T-cells then step up to fight off the infection.

But the immune system is even more clever than that. The B-cells make antibodies which attach to and scan the foreign substances. Once the substance is gone, the antibodies live on and if they encounter the same foreign substance again, they have a record of how to fight it off.

Vaccines exploit this mechanism by introducing a small (sometimes live, sometimes dead) dose of the virus into the body. The B-cells recognise the infection, make a note of it, and the T-cells kill it off. Because the B-cells have made a note, you usually can't get sick with the same germ again.

The problem with the current COVID-19 pandemic is that the coronavirus (or SARS-CoV-2) is a new virus to which nobody has had exposure before, so our bodies don't necessarily know how to fight it off.

The same is true for the flu virus and is why you need to take the flu vaccine every year, as the flu virus evolves over time. The antibodies remember last year's flu but don't have a record of this year's version.

'Boosting' the immune system

You've probably found hundreds of products and services that promise to boost your immune system, but as you may see from the above, all you really want is for your immune system to work optimally. An overactive immune system is also a problem. Allergy is an example of the immune system overreacting to a harmless substance.

An optimal immune system comes as part of an otherwise healthy body. If you exercise regularly and eat a varied diet with plenty of vegetables and fruit, chances are your immune system is working optimally.