The docked space shuttle Endeavour is featured in this image photographed by an STS-134 crew member onboard the International Space Station on May 21, 2011 during flight Day 6 activities. Earth's horizon and the blackness of space provide the backdrop for the scene.
Space is hardly an ideal place to become ill, and because of this, astronauts take precautions to avoid getting sick before a mission. But a long journey in space may actually compromise the immune system and make astronauts more susceptible to disease, a new study suggests.
The study was conducted in salamanders, and it's not clear if the same thing happens in humans. But the findings agree with those of several earlier studies on astronauts that have suggested space travel weakens the immune system.
The study "reinforces the need" to develop effective drugs or nutritional measures to bolster a weakening immune system, said study researcher Jean-Pol Frippiat, of the Université Henri Poincaré-Nancy in France.
Salamanders in outer space
Antibodies are proteins produced by the body's immune system to help fight off foreign invaders, such as bacteria and viruses. The antibody will bind to a specific part of the organism, and this target is known as the antigen. To make antibodies that bind tightly to antigens, antibodies mutate their genes at a high rate via a process called somatic hypermutation.
Frippiat and his colleagues used salamanders to study spaceflight's effects on somatic hypermutation. These amphibians use the same cellular mechanisms to generate antibodies as humans do. [6 Everyday Things That Happen Strangely in Space]
One group of salamanders remained on Earth and one was sent to space. The researchers then immunized the animals by injecting them with a cow protein. The salamanders should create antibodies to bind to this protein.
The salamanders in space carried out somatic hypermutation at a lower frequency than did the salamanders on the ground. That means that the quality of the antibodies in space was reduced and these salamanders would be less able to fend off invaders, Frippiat said.
Role of gravity
The study "brings together yet more evidence that the immune system is dependent on gravity," Millie Hughes-Fulford, a NASA science astronaut and molecular biologist, said in a statement.
"Dependence on gravity should be no surprise since all of Earth's jawed vertebrates developed in Earth's gravity, and it would be logical to expect that some systems would require gravity for normal function," Hughes-Fulford said.
The study is published online in the FASEB Journal.