A hundred years since Russian microbiologist Elie Metschnikow first discovered the invertebrate immune system, scientists are only just beginning to understand its complexity. Presenting their findings at a recent European Science Foundation (ESF) conference, scientists showed that invertebrates have evolved elaborate ways to fight disease.

By studying starfish, Metschnikow was the first to see cells digesting bacteria, a process he called phagocytosis (the eating of cells by other cells). Phagocytosis, it turns out, is an important immune defence in all living things. Since Metschnikows work, scientists have studied the immune systems of simpler organisms (such as invertebrates) in the hope of understanding the immune systems of more complex organisms, like us.

However, invertebrates immune systems are more elaborate than we expected. We have underestimated the complexity of invertebrate immunity, says Dr. Paul Schmid-Hempel, an evolutionary ecologist at the ETH Zurich in Switzerland. By studying the immune systems of fruit flies, mosquitoes and other invertebrates (including bed bugs, moths, crustaceans, worms, sponges and bees), scientists are finding new molecules involved in defences against pathogens (microbes that cause disease).

One molecule found in fruit flies, Dscam, is capable of folding itself in 18,000 different ways. Computer models that predict the structure of this molecule have led scientists to suggest that this folding creates different shapes, each capable of binding to different structures on the pathogens surface. These molecules can be used very flexibly by assembling their components in many ways, says Schmid-Hempel. Until now, this ability to recognize specific pathogens was thought to be limited to vertebrates.

In another exciting area of research, scientists showed the sophisticated ways that invertebrates manage their immune systems. Insects recognise peptidoglycan [a component of ba
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Contact: Paul Schmid-Hempel
psh@env.ethz.ch
European Science Foundation
21-Jun-2007