Persistent Impact of Smoking on the Immune System

Summary: Smoking not only affects immune responses in the short term but also leaves a lasting imprint on the body’s defense mechanisms. Through the Milieu Intérieur cohort of 1,000 healthy volunteers, the study identified smoking, alongside latent cytomegalovirus infection and body mass index, as a key factor influencing immune responses.

This groundbreaking research demonstrates that the effects of smoking on adaptive immunity can persist for 10 to 15 years after cessation, attributed to epigenetic changes in DNA methylation that alter gene expression involved in immune cell metabolism. This insight opens new avenues for understanding how lifestyle choices like smoking can have enduring effects on our health.

Key Facts:

  1. Smoking significantly impacts both innate and adaptive immune responses, with some effects persisting for up to 15 years after quitting.
  2. The study used the Milieu Intérieur cohort to demonstrate how smoking, latent cytomegalovirus infection, and body mass index are major factors affecting immunity.
  3. Long-term effects of smoking on immunity are linked to epigenetic changes, specifically DNA methylation, highlighting the durable influence of smoking on the body’s defense systems.

Source: Institut Pasteur

Like other factors such as age, sex and genetics, smoking has a major impact on immune responses.

This is the finding recently made by a team of scientists at the Institut Pasteur using the Milieu Intérieur cohort of 1,000 healthy volunteers, established to understand variability in immune responses.

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.

This shows an ashtray.
Basically, the immune system appears to have something resembling a long-term memory of the effects of smoking. Credit: Neuroscience News

These findings, which for the first time reveal a long-term memory of the effects of smoking on immunity, will be published in the journal Nature on February 14, 2024.

Individuals’ immune systems vary significantly in terms of how effectively they respond to microbial attacks. But how can this variability be explained? What factors cause these differences?

“To answer this key question, we set up the Milieu Intérieur cohort comprising 1,000 healthy individuals aged 20 to 70 in 2011,” comments Darragh Duffy, Head of the Translational Immunology Unit at the Institut Pasteur and last author of the study.

While certain factors such as age, sex and genetics are known to have a significant impact on the immune system, the aim of this new study was to identify which other factors had the most influence.”

The scientists exposed blood samples taken from individuals in the Milieu Intérieur cohort to a wide variety of microbes (viruses, bacteria, etc.) and observed their immune response by measuring levels of secreted cytokines.

Using the large quantities of data gathered for individuals in the cohort, 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 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.

As regards smoking, an analysis of the data showed that the inflammatory response, which is immediately triggered by infection with a pathogen, was heightened in smokers, and moreover, the activity of certain cells involved in immune memory was impaired. In other words, this study shows that smoking disrupts not only innate immune mechanisms, but also some adaptive immune mechanisms.

“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.”

Basically, the immune system appears to have something resembling a long-term memory of the effects of smoking. But how?

“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.”

It therefore appears that smoking can induce 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,” concludes Violaine Saint-André.

About this smoking and immune system research news

Author: Rebeyrotte Myriam
Source: Institut Pasteur
Contact: Rebeyrotte Myriam – Institut Pasteur
Image: The image is credited to Neuroscience News

Original Research: Open access.
Smoking changes adaptive immunity with persistent effects” by Darragh Duffy et al. Nature


Smoking changes adaptive immunity with persistent effects

Individuals differ widely in their immune responses, with age, sex and genetic factors having major roles in this inherent variability. However, the variables that drive such differences in cytokine secretion—a crucial component of the host response to immune challenges—remain poorly defined.

Here we investigated 136 variables and identified smoking, cytomegalovirus latent infection and body mass index as major contributors to variability in cytokine response, with effects of comparable magnitudes with age, sex and genetics.

We find that smoking influences both innate and adaptive immune responses. Notably, its effect on innate responses is quickly lost after smoking cessation and is specifically associated with plasma levels of CEACAM6, whereas its effect on adaptive responses persists long after individuals quit smoking and is associated with epigenetic memory.

This is supported by the association of the past smoking effect on cytokine responses with DNA methylation at specific signal trans-activators and regulators of metabolism.

Our findings identify three novel variables associated with cytokine secretion variability and reveal roles for smoking in the short- and long-term regulation of immune responses. These results have potential clinical implications for the risk of developing infections, cancers or autoimmune diseases.

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