Air pollution - whether from diesel exhaust in a big city or cooking-fire smoke in a developing nation - is bad for children with asthma. But although it's long been clear that breathing polluted air worsens lung-tissue inflammation in asthma, the biological mechanism by which pollution triggers that inflammation has been unclear.
Now, new research by Kari Nadeau, MD, PhD, assistant professor of pediatric immunology and allergy at Stanford, helps clarify the mystery. In a paper appearing online this week in the Journal of Allergy and Clinical Immunology, Nadeau and colleagues at Stanford and UC-Berkeley found that asthmatic children who live in an area with high levels of air pollution had impaired function of their regulatory T cells, a class of immune cells that keep inflammation in check.
Nadeau, who is also a pediatric immunologist at Lucile Packard Children's Hospital, compared asthmatic and non-asthmatic kids in two California cities: Stanford, which has low ambient air pollution, and Fresno, where the air is much more polluted. Asthmatic kids in Fresno had much worse regulatory T cell function than non-asthmatic Fresno children or any of the children living in Stanford. And the reduced T cell function was associated with worsened scores on a standard assessment of asthma symptoms. The non-asthmatic children in Fresno also had impaired T cell function compared to Stanford children, but the impairment wasn't as bad as in Fresno kids with asthma.
The study also gave some insight into how pollution interferes with T cells. Pollution exposure deactivates a specific transcription factor in T cells, part of the genetic code that helps genes switch on.
The results suggest a dose-response relationship, the researchers conclude. That is, the more pollution children breathe, the worse their asthma will get. Depressing, maybe, but the finding does have a silver lining: Even modest reductions in ambient air pollution have the potential to help kids with asthma breathe easier.
Photo credit: Brent Danley.