But a NASA study published in the Journal of Interferon & Cytokine Research has taken a small step for man's journey to distant planets. NASA scientists analyzed blood samples taken before, during, and after missions to the International Space Station, looking for indications of how astronauts' immune systems handle the unusual environment. The results indicate that things get a little bit wonky.
Some immune cells are heightened by the process of space travel, the researchers found, but others get depressed. That's why astronauts can experience the effects of a weakened immune system (like the asymptomatic viral seen in some, where a dormant virus starts producing new cells but not new symptoms) along with the effects of a heightened one (like increased allergies and persistent rashes).
This "immune dysregulation," NASA scientists said in a statement, is probably the result of a combination of factors. "Things like radiation, microbes, stress, microgravity, altered sleep cycles and isolation could all have an effect on crew member immune systems," Brian Crucian, Ph.D. and NASA biological studies and immunology expert, said. "If this situation persisted for longer deep space missions, it could possibly increase risk of infection, hypersensitivity, or autoimmune issues for exploration astronauts."
But it isn't certain that these changes would significantly increase the risks of long-term spaceflight. An upcoming year-long mission will provide further data for study. If the evidence suggests that immune system confusion could pose a threat to astronauts, the next step will be figuring out how to counteract it. Whatever they develop could make its way back to earth, providing new tools to help immune-compromised patients here at home.
To find out more about how space affects the human body, check out NASA's interactive on the subject.