Conquering Cat Allergy

The mechanism behind some people's allergic reaction to cat dander has finally been figured out.

By Valerie Ross|Thursday, January 9, 2014
Fesus Robert/Shutterstock

An estimated one in four people are allergic to cats.

Now, after learning how felines trigger such potent allergic reactions, researchers say new treatments may emerge.

Allergic reactions occur when the body’s immune system targets a normally harmless protein as if it were a dangerous pathogen, leading to inflammation. For people who are allergic to cats, that protein is Fel d 1, found in cat dander and the culprit behind allergy sufferers’ sneezes, wheezes, runny nose and watery eyes. But just how this protein triggers the immune system has been a mystery.

Human cells don’t respond to Fel d 1 alone, researchers at the University of Cambridge in England reported in July. It takes a third ingredient to get an inflammatory reaction: lipopolysaccharide, a molecule secreted by many common bacteria and therefore ubiquitous in the environment. When the researchers added a little of this bacterial byproduct to the mix, Fel d 1 activated a specific immune receptor on cells, called Toll-like receptor 4 (TLR4).

What’s more, the researchers found a way to keep Fel d 1 from causing an allergic response. If they treated tissue with a drug that blocked the activity of TLR4, the immune system did not flare up. “You could potentially inhale a dose of the inhibitor before entering into a room where cats were, and you hopefully wouldn’t get an allergic response,” says immunopharmacologist Clare Bryant, who led the study. The same inhibitor might be useful in thwarting other allergies as well.

[This article originally appeared in print as "Conquering Cat Allergy."]

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