CINCINNATI, Feb. 11 (UPI) -- U.S. researchers say cigarette smoke may result in the lung immune system attacking damaged tissue.
The study, published in the Journal of Clinical Investigation, found cigarette smoke setting off a molecular chain of events that activates a specific receptor -- NKG2D -- that spurs the immune system in a way that may lead to chronic obstructive pulmonary disorder, a narrowing of airways leading to breathing diseases such as emphysema.
"Our study is evidence that when the lungs are exposed to chronic damage from cigarette smoke, at some point that damage exceeds the body's natural ability to repair tissue and can start to contribute to COPD instead of protecting against it," lead investigator Michael Borchers of the University of Cincinnati said in a statement.
"People have historically believed that if you smoke, you suppress the immune system. We've shown that you actually activate certain parts of the immune system and it could potentially work against you."
Borchers' team found the correlation between cellular stress signals, immune system activation and COPD-like disease in a transgenic mouse model. Human tissue samples from non-smokers, smokers with COPD and smokers who did not develop COPD showed people who had never smoked lacked the NKG2D signal while current and former smokers who developed COPD activated this signal.
