Astronauts undergo a whole host of tests before, during and after their journey into space. The latest study to date looked at their immunity and showed that it decreased in microgravity conditions. Are you more likely to catch a bad cold in a spaceship than on Earth? Microgravity has negative consequences on the human body, such as bone and muscle loss, decrease in blood volume, or disruption of the immune systemimmune system. Indeed, scientists from the University of Ottawa, in Canada, have analyzed the immune cells of 14 astronautastronauts (eleven men and three women) who spent approximately six months in the International Space StationInternational Space Station (ISS). They drew their blood before leaving for space, several times on board the ISS and when they returned to Earth. “We have shown that the expression of many genes associated with immune functions decreases rapidly when astronauts reach space, while the opposite occurs when they return to Earth after six months in the ISS”, explains Odette Laneuville. , scientist at the head of this study published in Frontiers in Immunology. How to stay healthy in space when you are an astronaut? Space changes immunity A trip to space changes the expression of more than 15,000 genes present in white blood cellswhite blood cells. The scientists looked at 276 of them, the vast majority of which belong to the “decreased-then-increased” category, which includes genes whose expression decreases during the astronauts’ stay in space, then increases again when they leave. return to Earth to reach normal levels after a few months. Only the expression of 29 genes follows the reverse pattern; it increases when the astronauts are in space and decreases when they return to Earth. These results suggest that immunity declines rapidly when their body is in microgravitymicrogravity. For example, scientists have observed a drastic decrease in the CD3 marker on the surface of lymphocyteslymphocytes. This receptor is responsible for transmitting the alert signal of the presence of a pathogen to the lymphocytes and thus triggers their activation. Fortunately, CD3 gene expression returns to normal within days of returning to Earth. Preventing space infectionsDespite everything, Canadian scientists still believe that if astronauts encounter a pathogen during a space mission, their immune system’s response would not be optimal. They would also be more vulnerable to infections when they return to Earth, the time their immunity regains its full capacity – from a few weeks to a few months, depending on the individual. All this would be triggered by a redistribution of plasma in the body in microgravity conditions. It loses between 10 to 15% of its volume after a few days in space and circulates more in the upper part of the body. Scientists are considering a prophylaxis to limit these immune problems during future human space travel. A little wool probably won’t be enough to protect against a space cold. Article published on June 11, 2021 by Julie Kern Microgravity is not without consequences for the human body. It could weaken future interstellar travelers in the face of disease, by reducing the capacity for immunity. During a journey into space, the human body is put to the test. Without gravityterrestrial gravity, the muscular mass of the astronauts melts like snow in the sunsun; they also lose bone mass for example. Research has been very interested in the consequences of microgravity on human health since the first long-term space stays of astronauts in the MirMir station. Microgravity also upsets the balance of our immune system. Without fully understanding the mechanisms, it has been observed that it reduces our defenses against pathogens, allowing, for example, a virusvirus to replicate more quickly. A recent study, published in Scientific Reports, refines our knowledge on this subject. According to scientists at Stanford University, microgravity decreases the activity of T4 lymphocytes, T4 and T8 lymphocytes, but increases that of regulatory T lymphocytes. Offbeat Science: Microgravity Runs Astronauts’ Blood Upside Down Immune Cells Numbed by Microgravity…Blood Mononuclear Cells (PBMCs) from Eight Volunteers Were Subjected to Microgravity, or 1G Gravity for Testing, for 18 hours. After this treatment, the samples were left as is or were stimulated with antigens (ConA or an anti-CD28) to elicit an immune response. The reactions of each cell were studied using flow cytometry flow cytometry and the study of their mRNAmRNA. Their results indicate that microgravity decreases the responses, after stimulationstimulation, of T4 lymphocytes, whose role is, among other things, to activate B lymphocytes so that they differentiate and produce antibodies antibodies, T8 lymphocytes which destroy infected cells and NK (natural killer) cells, effectors of innate immunity that also kill infected cells. The secretion of cytokines, the moleculesmolecules that allow communication between all cells, also decreases in microgravity conditions, in particular TNFα, pro-inflammatory, CCL4, a molecule that attracts NK to the site of infection. …and regulators at attention On the other hand, the expression of regulatory T lymphocytes is increased in microgravity. As their name suggests, they are in charge of containing the immune response so that it does not attack the self. These cells are also involved in the prevention of autoimmune diseases. The overactivity of regulatory T in microgravity conditions further slows down the already weak immune response after stimulation. This is how microgravity puts our immune system to sleep. This could have serious consequences for the health of future travelers to other planets if, for example, a microbemicrobe infiltrates the spacecraft.