Smoking may cause immune overreaction

NEW HAVEN, Conn., July 25 (UPI) -- U.S. researchers say smoking induces a heightened -- rather than depressed -- immune response to flu.

This heightened immune response suggests why smokers may be more likely than non-smokers to die during influenza epidemics and are more prone to chronic obstructive pulmonary disease, the researchers said.

In a study using mice, Yale University researchers Dr. Jack A. Elias and Dr. Min-Jong Kang found the immune system overreacted in "smoking mice" exposed to a mimic of the flu virus and this exaggerated inflammation caused increased levels of tissue damage.

"The anti-viral responses in the cigarette smoke exposed mice were not only not defective, but were hyperactive," Elias says in a statement. "These findings suggest that smokers do not get in trouble because they can't clear or fight off the virus; they get in trouble because they overreact to it."

"If the exaggerated responses are verified in human studies, it will be the first explanation for why viral infections are more serious in smokers," Elia says. "Once verified, we can find ways to prevent the destruction of lung tissue and the higher illness and death among smokers."

The study is published in the Journal of Clinical Investigation.