Sitting on Cullen’s lab bench is a plastic box that houses a pair of mice. There are dozens more of these boxes in the basement of their building. Some of the mice are ordinary, but others are not: using genetic engineering techniques, Medzhitov’s team has removed the animals’ ability to make IgE. They can’t get allergies.

Medzhitov and Cullen will be observing these allergy-free mice for the next couple of years. The animals may be spared the misery of hayfever caused by the ragweed pollen that will inevitably drift into their box on currents of air. But Medzhitov predicts they will be worse off for it. Unable to fight the pollen and other allergens, they will let these toxic molecules pass into their bodies, where they will damage organs and tissues.

“It’s never been done before, so we don’t know what the consequences will be,” says Medzhitov. But if his theory is right, the experiment will reveal the invisible shield that allergies provide us.

‘Tough luck’



Even if the experiment works out just as he predicts, Medzhitov doesn’t think his ideas about allergies will win out as quickly as his ideas about toll-like receptors. The idea that allergic reactions are bad is ingrained in the minds of physicians. “There’s going to be more inertia,” he said.

But understanding the purpose of allergies could lead to dramatic changes in how they’re treated. “One implication of our view is that any attempt to completely block allergic defences would be a bad idea,” he said. Instead, allergists should be learning why a minority of people turn a protective response into a hypersensitive one. “It’s the same as with pain,” said Medzhitov. “No pain at all is deadly; normal pain is good; too much pain is bad.”

For now, however, Medzhitov would just be happy to get people to stop seeing allergies as a disease, despite the misery they cause. “You’re sneezing to protect yourself. The fact that you don’t like the sneezing, that’s tough luck,” he said, with a slight shrug. “Evolution doesn’t care how you feel.”

This is an edited version of an article originally published by Mosaic, and is reproduced under a Creative Commons licence. For more about the issues around this story, visit Mosaic’s website here.

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