



A new study suggests that long-duration space missions like a trip to Mars could take a severe toll on the immune systems of astronauts. For the study, researchers studied blood samples from eight astronauts who worked aboard the International Space Station for approximately six months. They discovered significant adverse impacts on "natural killer" (NK) cells, a class of white blood cell that kills cancer cells.

In a statement, the lead author of the study, Richard Simpson, an associate professor of nutritional sciences at the University of Arizona, said that when they look at the function of the astronaut samples during flight in comparison to their own samples before they flew, it goes down. When they compare them to controls who stayed on Earth, it still goes down. Thus he feels there is no doubt that NK-cell function is decreasing in the spaceflight environment when examined in a cell culture system.

Due to the importance of NK cells' in the immune system, this could be cause for concern for both astronauts and mission planners.

Simpson stated that cancer is a significant risk to astronauts during very prolonged spaceflight missions as a result of radiation exposure.

Simpson said that NK cells are vital to kill off virally infected cells, adding that when one is in the space station, it's a very sterile environment — so one is not likely to pick up the flu or a rhinovirus or some community-type infection — however the germs that are an issue are the viruses that are already in one’s body. These are mostly viruses that cause things such as shingles, mononucleosis, or cold sores; they stay in one’s body for the rest of one’s life, and they do reactivate when stress happens.

What’s more, stress may be a significant factor in the effect Simpson, and his colleagues observed. The team found that rookie spaceflyers suffered a more substantial drop in NK-cell functionality than veterans did.

Pinpointing exactly what's going on is the next step so that researchers can try to reduce the deleterious effect, as per the study team members.

Their study was published last November in the Journal of Applied Physiology, and the findings add to the long list of spaceflight-related health effects. For instance, vision problems can be an adverse effect of long-duration spaceflight, and it's known to decrease bone density and cause muscle atrophy (which is why crew-members must exercise vigorously every day.)







