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The Genetics of Allergies

Hereditary factors linked to more severe response to diesel fumes

THURSDAY, Jan. 8, 2004 (HealthDayNews) -- Allergy sufferers with certain genetic traits may suffer significantly worse symptoms when they're exposed to diesel engine air pollution.

That's the finding of a new study from the University of Southern California (USC) and the University of California, Los Angeles. Their report appears in the Jan. 10 issue of The Lancet.

"We've known that diesel exhaust particles worsen symptoms in individuals who respond to allergens, such as pollen, but this study suggests a direct way that pollution could be triggering allergies and asthma in a large number of susceptible individuals, and perhaps a new route of intervention," study author Dr. Frank D. Gilliland, a professor of preventive medicine at USC's Keck School of Medicine, says in a prepared statement.

The study included 19 people who were allergic to ragweed. Their DNA was tested to determine which forms of the GSTM1 and GSTP1 genes they had. These genes are responsible for producing enzymes that help the lungs detoxify pollutants and defuse oxidants before they can cause damage.

The GSTM1 gene occurs in two common forms -- present and null. The null form of the gene can't produce the protective enzymes. About 50 percent of people have the null form of the gene.

The GSTP1 gene can occur with a variation that causes it to produce a less effective enzyme. This gene variation occurs in about 40 percent of people.

It's estimated that 15 percent to 20 percent of people have both the null form of the GSTM1 gene and the GSTP1 gene variation.

Over a few months, the study subjects were twice given two treatments: nose spray with either a dose of ragweed allergen and diesel exhaust particles or spray with ragweed allergen and a placebo. The amount of diesel particles given was equal to the amount a person would inhale during a period of 40 hours in southern California.

The study found people who had the null form of GSTM1 had a larger allergic response to the diesel particles than others in the study. An even greater allergic response was observed in those who had both the null form of GSTM1 and the GSTP1 gene variation.

More information

Here's where you can learn more about air pollution and your health.

SOURCE: University of Southern California, news release, Jan. 8, 2004
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