From: Editor, ENN
Published October 25, 2013 09:22 AM

The Benefits of Allergies

For those of us that suffer from seasonal allergies, or even from indoor allergens like dust or mold, the symptoms that we have to these allergens is actually a positive reaction as two new studies show that our sneezing and wheezing may actually protect us.

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In a study involving reactions to bee stings, researchers report that mice that develop an allergic response to the venom in honeybee stings are more likely to survive potentially lethal doses of the same venom later on. 

In humans and other mammals, the immune system fends off unfamiliar and potentially harmful substances, in one of two ways. The so-called "type 1" reaction responds to viruses, bacteria, and other microbes by destroying them, while the "type 2" reaction uses an array of symptoms—including sneezing, coughing, and diarrhea—to expel allergens from the body.

Stephen Galli of the Stanford University School of Medicine in Palo Alto, California wanted to explore the effects of type 2 reactions, so he and his colleagues exposed mice to a common allergen: honey bee venom. They administered a dose of the venom—about as much as found in one or two bee stings—to two strains of mice: a type 1 response-prone strain and a type 2 response-prone strain. Two control groups of the same strains received no injections.

Eighty-six percent of the type 1-prone mice that had had an allergic reaction survived the dose, versus only 7% of the mice that weren’t allergic. Among the type 2-prone mice, 80% of the allergic mice survived, whereas only 28% of the nonallergic mice did. 

The results suggest that type 2 responses may have evolved to protect against venoms as well as parasites and that they're still serving this function, the team reports.

In a separate study, immunologist Ruslan Medzhitov of the Yale University School of Medicine and colleagues confirm that mice with a previous type 2 response to bee venom have a greater resistance to potentially lethal doses of the stuff later on and that IgE-lacking mice miss out on this protective effect. What's more, the team tracked down the venom ingredient that triggers the allergy—an enzyme called PLA2 that damages cell membranes and is found in the venoms of snakes, spiders, and many other creatures. "As far as I know, this is the first direct evidence that IgE-mediated responses can be protective and beneficial," Medzhitov says. "It's like the sensation of pain: It's very unpleasant, but very important for our protection."

The studies can be found in the journal Immunity.

Read more at Science/AAAS.

Bee image via Shutterstock.

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