Researchers show for the first time that smoking has a major long-term impact on our immune system, according to a study published in Nature. Even years after people quit smoking, the effect is still visible and affects the immune system.
To understand better how the immune system varies from person to person, in 2011, a team of researchers from the Institut Pasteur, France, set up the Milieu Intérieur cohort comprising 1,000 healthy individuals aged 20 to 70. Researchers know that factors such as age, sex and genetics significantly impact the immune system, but what other factors can also influence?
The authors exposed blood samples from participants in the Milieu Intérieur cohort to different microbes and observed their immune response. In addition, using all the data collected for each participant, the authors determined which of the 136 different factors — including body mass index, smoking, number of hours’ sleep, exercise, childhood illnesses, vaccinations, and living environment — impacted the immune responses most.
This analysis identified three factors: smoking, cytomegalovirus infection, and body mass index. “The influence of these three factors on certain immune responses could be equal to that of age, sex or genetics,” points out Darragh Duffy, Head of the Translational Immunology Unit at the Institut Pasteur and last author of the study.
When it comes to smoking, the results showed that in smokers the inflammatory response triggered by infection with a pathogen was poorer compared to non-smokers. In other words, this study shows that smoking disrupts how the immune system works. “A comparison of immune responses in 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,” observes Darragh Duffy. “This is the first time it has been possible to demonstrate the long-term influence of smoking on immune responses.”
Essentially, the immune system seems to “remember” smoking, even in ex-smokers. “When we realized that the profiles of smokers and ex-smokers were similar, we immediately suspected that epigenetic processes were at play,” says Violaine Saint-André, a bioinformatician in the Institut Pasteur’s Translational Immunology Unit and first author of the study. “We demonstrated that the long-term effects of smoking on immune responses were linked to differences in DNA methylation – with the potential to modify the expression of genes involved in immune cell metabolism – between smokers, ex-smokers and non-smokers.” In simple terms, smoking causes persistent changes to the immune system through epigenetic mechanisms.
“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,” concluded Violaine Saint-André.
Saint-André, V., Charbit, B., Biton, A. et al. Smoking changes adaptive immunity with persistent effects. Nature 626, 827–835 (2024). https://doi.org/10.1038/s41586-023-06968-8