BOSTON - Scientists have tracked down a mutant gene that appears to make people more susceptible to allergies.
Experts have long noticed that allergies run in families, and they believe that many genes, perhaps a dozen or more, are involved in this common condition.
The latest discovery, made at Washington University School of Medicine in St. Louis, implicates one that controls a single step in the inflammatory process that leads to asthma.
"We have found that if you have this mutation, you are 10 times more likely to be allergic," said Dr. Talal A. Chatila, one of the researchers.
Experts hope that they will be able to identify highly susceptible people by looking for this gene, and use it to tailor new therapies.
Allergies begin when the body mistakes proteins from cat dander, dust mites, cockroaches and other allergy-producing substances for dangerous invaders. A key step in the chain reaction that follows is production of IgE, an antibody that causes allergic reactions.
The gene that is mutated in some asthma victims contains the building instructions for a docking spot, or receptor, for the chemical called interleukin 4. This is a protein helps regulate the body's production of IgE.
The researchers found that 13 of 20 people with allergies had the variant receptor gene, compared with five of 30 who were free of allergies.
The study was conducted by Dr. Gurjit K. Khurana Hershey and others and published in Thursday's issue of the New England Journal of Medicine.