STUDY:

JOURNAL: Experimental Biology Conference

AUTHORS: Dr. Fred D. Finkelman

ABSTRACT: As many asthmatics know, a blast of diesel exhaust can trigger bouts of wheezing, coughing and other asthma symptoms. Now researchers say they have figured out why these fumes are so tough on those afflicted with the illness.

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COMMENTARY: The fine particles in diesel exhaust hit the human immune system with a double whammy, upping the production of an immune protein that triggers asthma attacks while suppressing a second protein that might otherwise bring symptoms to a halt.

Numerous studies have found that individuals living in urban areas or near busy highways are at much higher risk for asthma and other allergies compared with those living in less congested locales. While most experts have suspected diesel fumes as the prime culprit, until now the exact mechanism by which truck exhaust aggravates the immune system has remained unclear.

In their study, Finkelman and his colleagues injected small amounts of diesel exhaust particles into the bloodstreams of mice. The investigators found that, after injection, the mice secreted abnormally high levels of interleukin-6 (IL-6), an immune system protein "released by cells of the immune system in response to substances such as bacteria and viruses that the immune system perceives as dangerous." In the asthmatic lung, this response can go overboard, triggering airway constriction, coughing and congestion.

Luckily, the immune system has a kind of countering mechanism, a protein called interferon-gamma. When released in large quantities, interferon-gamma works to put the brakes on runaway immune responses.

Diesel exhaust appears to dampen interferon-gamma production--giving IL-6 free reign to trigger asthmatic symptoms.