Smoking impairs immune response, even acter qui ing, new study says

Public health messages have told us for decades that if you smoke, you should quit. And if you don’t smoke, don’t start. But a new study suggests smoking may be even worse than we thought.

The study, published Wednesday in Nature, underscores the importance of never lighting up that Drst cigarette, based on its conclusion that smoking has much longer harmful effects on immune responses than previously understood.

People who quit smoking soon regained normal function of their immune system’s power to mount fast and general innate responses to bacteria or viruses. But researchers also found that slower, more targeted adaptive T cell defenses remembered from past pathogens did not come back so soon after that last cigarette.

“We could see that the effect of active smoking on in/ammatory responses to bacterial stimulation were lost when individuals quit smoking,” senior study author Darragh Duffy of the Institut Pasteur said about the innate response on a call with reporters. “In contrast, the effect on the T cell response was maintained for many years after the individuals quit smoking.”

These results come from the Milieu Int´erieur project, a longterm study of healthy people in France exploring the impact of environmental factors on immune responses. For this study, 1,000 participants answered questionnaires about 136 diet, lifestyle, demographic, and socioeconomic factors. They also gave blood samples for laboratory tests in which the scientists stimulated production of 13 cytokines, molecules involved in the body’s immune defense, in response to 12 proteins active in microbial and viral infections.

Three factors stood out as important in how immune responses varied: smoking, body mass index, and infection with cytomegalovirus (a member of the herpes family).

People who smoked had increased in/ammatory responses, but those higher levels were transient, dropping after smoking cessation. But the effects on the adaptive response persisted for many years after quitting, changing the levels of cytokines released after infection or other immune challenges.