Although we can inherit the genetic predisposition to develop certain diseases, our lifestyle and environment play a key role in health and in the way our immune system manifests itself to protect us against external threats. Our sex and age also influence, and now a new study carried out by scientists at the Pasteur Institute (France) reveals that smoking has a significant impact on immune responses and that, in fact, tobacco consumption is the factor that causes the most alterations in our defenses, changes that in some cases are temporary, but, in others, can be maintained in the long term.
The researchers used data from 1,000 healthy volunteers between 20 and 70 years old – included in the ‘Milieu Intérieur’ cohort that was created in 2011 – to understand the variability in immune responses, and found that in addition to the short-term effect that smoking on immunity, this habit also has long-term consequences and, for many years after giving up tobacco, smokers suffer effects on some of the body’s defense mechanisms acquired while smoking. The findings have been published in the journal Nature and reveal for the first time a long-term memory of the effects of smoking on immunity.
How tobacco influences immunological memory
The effectiveness with which people’s immune systems respond to pathogen attacks varies significantly, and the study authors investigated the reasons for this variability and the factors influencing the differences. 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 the levels of secreted cytokines (proteins involved in immune defense).
Thanks to the large amount of data collected on the individuals in the cohort, they were able to determine which of the 136 variables investigated (body mass index, smoking, hours of sleep, exercise, childhood illnesses, vaccines, living environment…) had had the greater 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 the same as that of age, sex or genetics,” says Darragh Duffy, head of the Translational Immunology Unit at the Pasteur Institute and one of the authors of the study.
Regarding smoking, the analysis of the data showed that in smokers the inflammatory response that is triggered immediately by infection with a pathogen was intensified and, in addition, the activity of certain cells involved in immune memory was altered. That is, the results show that smoking not only alters 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,” notes Darragh Duffy. “This is the first time that the long-term influence of smoking on immune responses has been demonstrated.”
“The inflammatory response returned to normal levels quickly after smoking cessation, while the impact on adaptive immunity persisted for 10 to 15 years.”
They observed that the immune system appears to have something similar to a long-term memory of the effects of smoking. “When we realized that the profiles of smokers and ex-smokers were similar, we immediately suspected that epigenetic processes were at play,” explained Violaine Saint-André, bioinformatician at the Translational Immunology Unit of the Pasteur Institute and first author of the article.
“We showed that the long-term effects of smoking on immune responses were related 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” . Therefore, it appears that smoking can induce persistent changes in the immune system through epigenetic mechanisms. “This is an important discovery that clarifies the impact of smoking on the immunity of healthy people and also, in comparison, on the immunity of people suffering from various diseases,” concludes Violaine Saint-André.
In statements to SMC Spain Africa González-Fernández, professor of Immunology and researcher at the Biomedical Research Center of the University of Vigo (CINBIO), who has not participated in the study, says: “In this work they have shown that being a smoker modifies the immune system. immune. But the important thing is that it does so persistently and that even when you stop smoking its effects last. If a person stops smoking, he recovers the innate immunity part well, but not the adaptive immunity (mediated by lymphocytes). This would indicate that there would be a persistent ‘memory of having smoked’ in the immune system, which has an important implication, since smokers can develop other diseases such as cancer, autoimmunity or allergies, or respond abnormally to infections. ”.
“It is very surprising that, while the alterations produced in the non-specific response revert after quitting this habit, thus reaching normality, the important changes observed in the specific response are maintained for years after stopping smoking. The authors also demonstrate that these changes are the consequence of modifications induced by tobacco in the regulatory mechanisms of important genes of the immune system, and if tobacco affected the regulation of other genes other than those studied in a similar way, this “could explain why tobacco is such an important risk factor in the development of tumors in organs other than the lung,” says Ignacio J. Molina, professor of Immunology at the University of Granada and researcher at the Biomedical Research Center of Granada. in statements to the same medium.
Marcos López Hoyos, president of the Spanish Society of Immunology (SEI), scientific director of the Valdecilla Health Research Institute (IDIVAL) and professor of Immunology at the University of Cantabria, has highlighted that this work “helps explain possible alterations in the immune response.” that we frequently see in the clinic of smokers (and usually overweight) who reach the age of 60 with suspicion of immunodeficiency secondary to smoking in the context of chronic obstructive pulmonary disease (COPD) and where we see relatively frequently a hypogammaglobulinemia [baja concentración de anticuerpos]”.
