What is the immune system?

Organs of the immune system

Cells of the immune system

Australia: leader in immunology

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What is the immune system? 

Every day your body is being attacked by foreign organisms such as bacteria, viruses and parasites that can cause disease. These are called pathogens.

Humans have evolved a complex system of cells and chemicals which are released from cells to protect you from these invaders. This is called the immune system

Components of your immune system travel around your body through the blood and lymph fluids patrolling for invading pathogens. Once a pathogen is recognised, the immune system swings into action to eliminate it. Parts of the pathogen may be broken down and recognised by the immune system as foreign material. These are called antigens.

Your immune system can also protect you from your own cells that are either over activated and can cause autoimmune conditions or that have become mutated and can cause cancer.

We can activate or suppress the immune system to protect ourselves from disease. Vaccines are used to boost the immune system against a certain pathogen. If the pathogen then attacks the body, the immune system is primed and ready to go. On the other hand, for organ transplants immunosuppressive drugs are used to quieten the immune system, so that the skin graft is not seen as foreign and is not attacked by the immune system and rejected.

Download the International Day of Immunology booklet for information about the immune system.