The harms of smoking are many, but new research offers evidence of another troubling type of harm: Smoking alters the immune system, leaving you more vulnerable to disease and infection even years after you quit.
Smoking changes adaptive immunity with persistent effects Summary Individuals differ widely in their immune responses, and age, sex, and genetic factors play an important role in this inherent variability. However, the variables driving such differences in cytokine secretion (a crucial component of the host response to immunological challenges) remain poorly defined. Here we investigated 136 variables and identified smoking, latent cytomegalovirus infection, and body mass index as the major contributors to variability in cytokine response, with effect sizes comparable to age, sex, and genetics. We found that smoking influences both innate and adaptive immune responses. In particular, its effect on innate responses is lost rapidly after smoking cessation and is specifically associated with plasma CEACAM6 levels, while its effect on adaptive responses persists long after individuals stop smoking and is associated with epigenetic memory. This is supported by the association of the effect of past smoking on cytokine responses with DNA methylation in specific signal transactivators and regulators of metabolism. Our findings identify three novel variables associated with the variability of cytokine secretion and reveal the role of smoking in short- and long-term regulation of immune responses. These results have potential clinical implications on the risk of developing infections, cancers or autoimmune diseases. |
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“Quit smoking as soon as possible,” study co-author Dr. Violaine Saint-André , a computational biology specialist at the Pasteur Institute in Paris, told CNN. "The key message from our study, especially for young people, is that there appears to be significant interest in long-term immunity to never start smoking."
The findings, published February 14 in the journal Nature , show how smoking reduces the body’s ability to fight infections and may also increase the risk of autoimmune diseases such as rheumatoid arthritis and lupus.
"The main discovery of our study is that smoking has short-term but also long-term effects on adaptive immunity associated with B cells and regulatory T cells and with epigenetic changes," said Saint-André.
To reach that conclusion, French scientists looked at blood samples collected over time from a group of 1,000 healthy people between 20 and 69 years old.
The researchers wanted to see how numerous variables, including lifestyle, socioeconomic status, eating habits, age, sex and genetics, affected the immune response. During the study, they exposed blood samples to common germs such as E. coli bacteria and the flu virus and at the same time measured the immune response.
What did they discover?
Smoking, body mass index, and a latent infection caused by the herpes virus had the greatest impact on the immune system, with smoking showing the greatest effect of all.
Even when smokers in the study quit, their immune response did not fully recover for years, study co-author Dr. Darragh Duffy , who heads the Translational Immunology unit at the Institut Pasteur , told CNN .
"The good news is that it is starting to be restored," he said. "There is never a good time to start smoking, but if you are a smoker, the best time to quit is now."
The study also found that the more people smoked, the more it altered their immune response.
Smoking appeared to have long-term effects on the immune system’s two main defense fronts: the innate response and the adaptive response. The effect on the innate response quickly disappeared when someone stopped smoking, but the effect on the adaptive response persisted even after quitting smoking.
The innate immune response is the general and immediate way to fight germs. When the body determines that the innate response is not sufficient, the adaptive immune system goes into action. Made up of antibodies, B cells, and T cells, the adaptive immune system can remember a threat and better attack threats it has seen before.
Dr. Albert Rizzo, chief medical officer of the American Medical Association, told CNN that the findings appear to explain why even smokers who have quit can develop conditions such as chronic obstructive pulmonary disease (COPD). "This study is useful because it tells us what we’ve always thought, but now it begins to explain why," Rizzo said.
