For millions of years, parasitic worms have had to survive inside animals without being destroyed by their hosts’ immune systems. To do that, they have evolved remarkably effective ways of dampening the immune response.

Scientists are now trying to understand those tricks and work out whether they could be turned into medicines for diseases resulting from overactive immune systems.

Parasitic worms, also known as helminths, include roundworms, tapeworms, hookworms and flukes. Many live and feed in the intestines of their hosts, including humans. They still infect up to 1.5 billion people worldwide each year.

Although they can be unpleasant, these parasites deserve some grudging respect. They have evolved ways to survive inside their hosts for years and even decades. For scientists interested in autoimmune, inflammatory and allergic conditions, that’s a remarkable skill.

The human immune system walks a constant tightrope – it must be aggressive enough to fight off viruses, bacteria and parasites, but controlled enough to avoid damaging the body’s own tissues. Sometimes that balance breaks down.

There are three main ways the immune system can turn against its host. In autoimmune diseases, the immune system mistakenly attacks the body’s own cells and tissues. In........

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