Woman wearing a protective mask

Staying alive

What’s the immune system for?

Every day, your body could succumb to hundreds of different infections or harmful substances. It is constantly under attack from microbes, parasites and other threats. The only reason you’re not sick all the time – and probably the only reason you’re alive today – is that your immune system deals with these assaults. It does so through processes and structures that try to prevent invasion, but it can also fight off an infection or disease that tries to take hold.

Vertebrates, including humans, have very sophisticated immune systems that adapt during a lifetime to take account of specific organisms and substances that enter the body. Most other animals and plants have immune systems too, even if they look different from ours. Both plants and animals have receptors on their cells that can recognise invading microbes.

Plants, however, don’t have patrolling immune cells like we do, so infection has to be dealt with by ordinary cells at the site of infection. And even some of the organisms that attack us have their own immune systems. For example, we’re only just beginning to understand those found in bacteria.

Lead image:

Woman wearing a protective mask.

Dan Foy/Flickr CC BY NC


About this resource

This resource was first published in ‘Immune System’ in January 2015.

Microbiology, Immunology
Immune System
Education levels:
14–16, 16–19, Continuing professional development