Rights: The University of Waikato Published 18 October 2010 Download

Professor Graham Le Gros from the Malaghan Institute explains the body’s defence system. He talks about the first line of defence, which involves the skin barrier. He then talks about how pathogens can get behind this barrier into deeper tissues. This calls for the immune system – cells designed to hunt down and kill the worst bugs that we face.


First of all, we have the basic skin barrier, and then underneath that, we have the blood. We all know pusy infections or pimples or whatever. Often they are the body’s first line of defence – the immune system immediately getting these white cells, which can actually kill off relatively harmless bugs.

And then there are these things called pathogens, really nasty bugs. Flu virus is one, hookworm is another one, malaria is another one, tuberculosis – these bugs have learnt how to go behind the white blood cells, the pus cells, and start infecting the deeper tissues. And for that, we need what we call the adaptive immune system. These are cells specifically designed to really hunt down the worst bugs that we face, and they have specific weapons to kill them that the other white cells that cause the pus don’t have.

So you have got to think about the immune system as layers, you know, first barriers, then first line of defence, the sort of marines, and then the more sophisticated nuclear guided missiles that come in later and get past all that etc. And it does a tremendous job of actually staying pretty calm, because when it sets off a nuclear missile, for instance, it damages the whole area, there is collateral damage, it doesn’t just get the bug, it tends to get the bit of tissue around it. And that’s going back to what asthma and allergy is – you’ve actually got these immune system cells designed to kill parasites, thinks the parasite is there, sets off its bombs, and there is a bit of collateral damage in the tissue around, thinking that is where the parasite is, and that causes the allergic disease.

Lucas Rucchin, I Stockphoto
Jennifer Sieber
Richard Sequeira, Maurice Wilkins Centre for MolecularBiodiscovery
C. S. Goldsmith and A. Balish, CDC Centres for Disease Control & Prevention
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Janice Haney Carr, CDC Centres for Disease Control & Prevention
CDC Centres for Disease Control & Prevention
Analytical Imaging Facility at the Albert Einstein College of Medicine.
uberstock I Stockphoto.com