The effects of space travel on the immune system of astronauts have been a topic of scientific interest. Extended stays in space, such as on the International Space Station (ISS), can lead to changes in the immune system, which can potentially impact the astronauts’ health.
1. Susceptible to infections
A recent study published in Frontiers in Immunology shed more light into the mechanisms behind the breakdown of the immune system in space. The research, involving 14 astronauts who spent extended periods (between 4,5 and 6,5 months) aboard the ISS, brings essential insights into why astronauts are more susceptible to infections during their missions, revealing the weakening of their body’s defense against pathogens.
The scientific work was led by molecular biologist Odette Laneuville, from the University of Ottawa in Canada, and examined gene expression in leukocytes — white blood cells — isolated from blood drawn from the astronauts. The team, consisting of researchers from the Canadian Space Agency and NASA, conducted blood samples before the flight, during the astronauts’ time aboard the ISS, and after their return to Earth.
2. Immune suppression
Previous studies have shown that space travel can lead to immune suppression, meaning the immune system becomes less effective in defending against pathogens. While the exact mechanisms behind this suppression are not fully understood, the scientific community believes that factors such as microgravity, radiation exposure, stress, and altered sleep patterns may play a role.
However, the findings of Laneuville’s study showed that gene expression in leukocytes decreased significantly upon reaching space, reaching approximately one-third of the normal levels. This decline occurred within the first few days in space and remained stable throughout the mission. Upon returning to Earth, the genes gradually returned to their normal behavior within about a month.
Before this paper, we knew of immune dysfunction but not of the mechanisms.Guy Trudel, rehabilitation medicine specialist from the Ottawa Hospital
“White blood cells are very sensitive to the environment of space. They trade their specialized immune functions to take care of cell maintenance or housekeeping roles”, explained study co-author Guy Trudel, a rehabilitation medicine specialist from the Ottawa Hospital.
3. ’Fluid Shift’
This altered behavior, the researchers said, may result from a phenomenon called “fluid shift” in which blood in the absence of Earth’s gravitational pull is redistributed from the lower to the upper part of the body. It is unlikely that greater solar radiation exposure in space was the culprit, they added.
Weaker immunity increases the risk of infectious diseases, compromising astronauts’ ability to perform their demanding work in space. Moreover, if the astronauts do require serious medical assistance, the ISS may not have the conditions to provide the necessary care. Now, the research team is focused on developing specific countermeasures to prevent immune suppression during long-duration space flights. Scientists and space agencies continue to investigate the mechanisms underlying immune system alterations in space and explore potential countermeasures to mitigate the negative effects.