Diesel Fumes Aggravate Response to Airborne Allergens

Researchers studying the genetic factors that determine the risk of developing allergies have used a model system combining ragweed pollen with diesel fumes to show that individuals with defects in the family of antioxidant-related genes (GSTM1, GSTT1, and GSTP1) are more likely to suffer allergic reactions than those with normal GST activity.

Investigators at the University of Southern California (Los Angeles, USA; www.usc.edu) exposed volunteers with ragweed allergy to controlled doses of ragweed pollen followed by either a placebo or by diesel exhaust particles equivalent to breathing the air in Los Angeles for 40 hours. Nasal allergen-specific IgE, histamine, interleukin 4, and interferon-gamma concentrations were measured before and 24 hours after challenge. Genomic analyses were performed to determine which genes became activated.

Results published in the January 10, 2004, issue of The Lancet revealed that the mix of ragweed and diesel exhaust triggered greater allergic responses than ragweed alone. Individuals lacking GSTM1 or carrying the GSTP1 I105 wild type genotype showed enhanced nasal allergic responses in the presence of diesel exhaust particles. Compared with patients with a functional GSTM1 genotype, patients lacking GSTM1 had a significantly larger increase in IgE and histamine.

"Diesel emissions can trigger allergic symptoms, but the genetic factors involved in the process are quite complex,” explained senior author Dr. David Diaz-Sanchez, assistant professor of immunology and allergy at the University of Southern California. "Our findings suggest that people who lack the genes to make key antioxidants may have difficulty fighting the harmful effects of air pollution.”



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