Ozone Breaks Down Lungs' Defenses

It kills off immune cells that typically fight bacteria, study finds

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MONDAY, Oct. 1, 2007 (HealthDay News) -- Ozone, a major component of urban air pollution, shuts down early immune responses in the lungs, which in turn makes the lung more vulnerable to bacteria and other foreign invaders, research shows.

It's known that exposure to ozone is associated with increased cardiovascular and pulmonary hospitalizations and deaths, but the actual mechanisms involved haven't been clarified. This study, by Duke University Medical Center pulmonary researchers, may provide some answers.

They found that mice exposed to unhealthy ozone levels showed amplified lung injury in response to bacterial toxins. The rodents also showed increased "programmed cell death" of the type of innate immune system cells that normally devour foreign invaders and keep the airways clear.

The innate immune system -- the most primitive part of the body's defenses -- reacts indiscriminately to any invader.

"Small amounts of inhaled foreign material can be relatively harmless, since they stimulate an appropriate innate immune response that protects the lungs," study lead author and pulmonologist Dr. John Hollingsworth, said in a prepared statement.

"However, it appears that ozone causes the innate immune system to overreact, killing key immune cells, and possibly making the lung more susceptible to subsequent invaders, such as bacteria," he said.

The study is published in the Oct. 1 issue of the Journal of Immunology.

More information

The American Association for Respiratory Care has more about ozone air pollution.

SOURCE: Duke University, news release, Oct. 1, 2007

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