GSTM1 occurs in two common forms in the population-either "present" or "null." Differences between present and null forms are small, but they may mean a lot. People born with two of the null form of the gene cannot produce the GSTM1 protective enzyme at all. About 50 percent of the population falls into this category.
Meanwhile, the GSTP1 gene can occur with a common variation called ile105. People born with two of the ile105 form of the gene produce a less-effective form of the GSTP1 enzyme. This less-effective form occurs in about 40 percent of the population.
In this clinical trial, the research team enrolled 19 people with known allergies to ragweed. They sampled participants' DNA to discern which forms of the GSTM1, GSTP1 and other similar genes they had.
Over the next few months, researchers twice gave each participant two treatments: nose spray containing either a dose of ragweed allergen and diesel exhaust particles or spray containing ragweed allergen and a placebo. The amount of diesel particles given was about what someone would experience during 40 hours spent in Southern California.
After administering the spray, researchers measured participants' nasal allergic episodes. They found that participants who lacked the GSTM1 enzyme had a larger allergic response than others. Also, those participants who lacked GSTM1 and had at least one GSTP1 ile105 genetic variant had an even larger allergic response to diesel exhaust particles than did the participants with the other versions of the genes. Researchers estimate that 15 to 20 percent of the population has both genetic variations. This represents a large group especially susceptible to the adverse effects of air pollution.
Further studies are needed to find other geneti
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Contact: Jon Weiner
jonweine@usc.edu
323-442-2830
University of Southern California
8-Jan-2004