Gastroenteritis, colds, tonsillitis: every winter is the same thing, there are those who chase infections and those who seem protected against all surrounding microbes.

Will viruses and bacteria have favorite targets, or do some people develop a parry for the ills of winter? The answer is more complex, at least as much as our immune system! But recent research helps to better understand why some of us are more fragile, and open avenues to better protect them.

Precious Bacteria

To protect itself, the body has different barriers, starting with the skin and mucous membranes, major interfaces with our environment. In addition to mechanical protection, especially against cold, heat, shock, they also shelter different bacterial populations that help to control microbial invasions. Cold and dry air, linked to the winter season, but sometimes to poorly regulated air conditioning, dry out the mucous membranes and open the way for pathogens that can penetrate the airways more easily.

Nestled deep within our digestive tract, gut microbiota bacteria would also be valuable in dealing with infections. “Although we still have a lot to discover in the precise role they play, it seems quite plausible today that there are relationships between these intestinal bacteria and cells of immune system,” said Pr Jacques Schrenzel. The doctor recounts the results of recent work indicating that differences in the microbiota of patients could modulate the response to immunotherapies against cancer.

Genetic Mutations

At the cellular level, it is the immune system that is the guarantor of our resistance to infections. However, dysfunctions can occur very early, from the first days of life. They are due mostly to genetic mutations, not always well known. “These are rare diseases, and we are still discovering new cases of genes involved in the immune response,” says Pre Klara Posfay-Barbe, head of the General Pediatrics Department at the HUG Children’s Hospital. will present his inaugural lesson “Infection: as soon as we stop defending, we must take the offensive”, on February 8 at the University of Geneva *. The “offensive” passes for some children by a bone marrow transplant. For others, regular immunoglobulin injections are also an option, to supplement the deficient immune system. In some cases, the mutation does not jeopardize all immunity, but increases susceptibility to certain pathogens (meningococci, pneumococci), or makes the symptoms particularly severe (influenza). Nothing can cure these children, but vaccination, or prophylactic antibiotic therapy, may help to protect them better.

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Aging System

If one part of our immunity is called “innate”, the other part is built up over time. “The immune system does not reach maturity until around 5-7 years,” said the pediatrician. The specialist recalls that the maturation of the immune system also depends on exposure to microbes. “It is quite normal for children who are at the nursery to be more often sick the first year. After all, everything is back to normal, and they’re better protected.”

But it is for the immune cells as for memory: the years that pass them undermine. “There is indeed an aging of the immune system, says Pre Posfay-Barbe. This explains in particular that common viruses wake up in the elderly. “More than half of over 80 years and develop shingles, infection related to the resurgence of the chickenpox virus. Another problem for seniors, this decrease in immunity reduces the effectiveness of vaccines. Making vaccines more immunogenic for these people is thus a major area of ​​research.

Because for the most fragile, vaccination remains one of the best tools of protection. “Developing new vaccines for these at-risk populations may be useful, but it should already be used properly,” says Klara Posfay-Barbe. At the HUG, for example, we developed a vaccination program for all liver transplant patients, and we realized that many were not up to date in the vaccination schedule. “But all transplant patients follow, for life, a treatment that avoids rejection of the graft but at the cost of a decrease in the effectiveness of their immunity and therefore a greater vulnerability to infections.

Take care of your Lifestyle

Take care of your Lifestyle

For those who are in good health and would like to stay, is it possible to “boost” its immunity, as claimed by so many products in the wellness departments of stores? “To my knowledge, there is no miracle substance,” smiles Klara Posfay-Barbe, who recalls the difficulty of testing all items on the market with solid methodology. In addition to unproven efficacy, some dietary supplements can be dangerous, so consumers should be careful about where the products come from and talk to their doctor if they are on treatment.

In everyday life, to cope with infections, a healthy lifestyle is the best weapon. A balanced diet, rich in plants, and especially quality sleep are essential for the proper functioning of immune cells. The response to vaccines is therefore poorer in those who do not sleep enough, while the risk of getting cold is four times lower than six hours of sleep per night. Finally, chronic stress and tobacco are now considered two major enemies of our natural defenses.

Cancers: A Failure of Immunity?

Viral or bacterial infections are not the only targets of the immune system. For nearly half a century, scientists have tried to show that it also attacks cancer cells. It is finally the recent success of treatments that activate immunity, immunotherapies, that came to support this hypothesis. “We now know that the immune system eliminates abnormal cells. If this equilibrium breaks down, tumor cells can proliferate, explains Professor Olivier Michielin, Head of Analytical Oncology at the Vaud University Hospital Center (CHUV). Today an immune system escape is considered a necessary step in the development of cancer. “And the strategies of tumor cells to” escape “our lines of defense are complex. They can become less immunogenic, so less identifiable by lymphocytes, or deprive them of essential elements to their proper functioning, and even divert to their advantage self-regulation mechanisms usually use to protect us from autoimmune diseases.



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