By Heather Close, Kentucky Health News

Like other factors such as age, sex and genetics, smoking has a major impact on immune responses, say a team of French scientists in a research paper that they say reveals for the a long-term memory of the effects of smoking on immunity, through molecules that attach to a smoker’s DNA.

In addition to its short-term impact on immunity, smoking also has long-term consequences. For many years after they have quit the habit, smokers are left with effects on some of their bodies’ defense mechanisms acquired while smoking, says the paper, published in the journal Nature.

Researchers at the Institut Pasteur used a sample cohort of 1,000 healthy volunteers to understand how effectively they respond to attacks from viruses and bacteria. They exposed blood samples to the micronbes and measured the immune response. “The team then determined which of the 136 investigated variables (body mass index, smoking, number of hours’ sleep, exercise, childhood illnesses, vaccinations, living environment, etc.) had the most influence on the immune responses studied.

Three variables stood out: smoking, latent cytomegalovirus infection (a virus in the herpes family that is often asymptomatic though dangerous to fetuses) and body mass index,” says a news release that quotes researcher Darragh Duffy: “The influence of these three factors on certain immune responses could be equal to that of age, sex or genetics.”

The inflammatory response was greater in smokers, and “the activity of certain cells involved in immune memory was impaired,” the release says. “In other words, this study shows that smoking disrupts not only innate immune mechanisms, but also some adaptive immune mechanisms… .  The immune system appears to have something resembling a long-term memory of the effects of smoking.”

A comparison of smokers and ex-smokers “revealed that the inflammatory response returned to normal levels quickly after smoking cessation, while the impact on adaptive immunity persisted for 10 to 15 years,” Duffy said. “This is the first time it has been possible to demonstrate the long-term influence of smoking on immune responses.”

The researchers found that those effects involve changes to the smoker’s DNA — not the genetic material itself, but the addition of methyl-group molecules to DNA, “changing the way in which the genome is read in the cell,” thus affecting the immune response, the release says.

Researcher Violaine Saint-André said, “This is a major discovery elucidating the impact of smoking on healthy individuals’ immunity and also, by comparison, on the immunity of individuals suffering from various diseases.”