Long journeys into space could paralyze the immune system of astronauts

This study has implications for NASA, which hopes to send humans to Mars by 2030 for a round-trip mission that could last up to three years – much longer than any human has ever spent in the world. 'space.

"NASA and other space agencies are worried about whether the immune system will be compromised during very long space flight missions," said Richard Simpson, lead author of the study. "What are the clinical risks to astronauts during these missions when they are exposed to problems such as microgravity, radiation and isolation stress? Could this be catastrophic to the point that the astronaut is not able to carry out his mission? "

The team studied the effects of spaceflights of six months or more on NK cells (NK cells), a type of white blood cell that kills cancer cells in the body and prevents old viruses from reactivating.

"Cancer represents a significant risk to astronauts during very long space flight missions due to radiation exposure," Simpson said. "[NK-cells] are also very important for killing cells infected with the virus. When you are in the space station, the environment is very sterile – you probably do not get the flu, a rhinovirus or a community-type infection – but the problematic infections are the viruses already in your body. system. body.

"These are mostly viruses that cause things like shingles, mononucleosis or cold sores; they stay in your body for the rest of your life and reactivate when you're stressed. "

Scientists compared blood samples from eight crew members who flew missions to the International Space Station with healthy individuals left on Earth. Blood samples were collected before launch, at several points during the mission and after the astronauts returned to Earth.

The results showed that NK cell function is altered in astronauts compared to pre-flight and ground control levels. At day 90, cytotoxic activity of NK cells against leukemic cells in vitro The number of crew members has been reduced by around 50%.

"When we look at the function of flying astronaut samples versus their own samples before they fly, they collapse. When we compare them to the controls that have remained on Earth, it keeps going down, "said Simpson. "I do not think there is any doubt that the function of NK cells decreases in the space flight environment when it is badyzed in a cell culture system."

The effect seems to be more pronounced in novice astronauts, as opposed to those who have already been in space.

"Fortunately, we found that half of our crew members had already flown, and the other half had not done so," Simpson said. "So we could split them in half to see if there was an effect, and there was. "Recruits" had larger declines in NK cell function than veterans. "

The differences could be more or less stressful, baduming that novice astronauts, generally younger than their experienced counterparts, find the space travel more stressful than those who have already done so.

While declining NK cell function makes astronauts more vulnerable to cancer, it remains to be seen whether the virus will reactivate, making viral reactivation even more difficult, Simpson said. He hopes to learn more about future studies.

"The next question would be: how can we mitigate these effects? How to prevent the immune system from degrading when traveling in space? ", Did he declare. "To do this, you must first understand what is causing the decline: is it stress? Is it microgravity? Is it a radiation? Is it a plethora of things? Once we understand this, we can try to find ways to directly target and mitigate these factors. "

Simpson and his colleagues at NASA's Johnson Space Center, as well as European and Russian scientists, are already working on countermeasures that can help astronauts stay healthy in the space, including nutritional or pharmacological interventions. an increase in exercise a positive effect on the functioning of the immune system.