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Immune System: Changes in Space

Astronaut Leroy Chiao, Expedition 10 commander and NASA ISS science officer, equipped with a bungee harness, exercises on the Treadmill Vibration Isolation System (TVIS). Exercise helps keep humans’ immune systems functioning properly.We know that the space environment can have detrimental effects on astronauts. NASA’s researchers are concerned about keeping astronauts as healthy as possible in space, so they are investigating how the immune system reacts to spaceflight. The following information provides a summary of what researchers have discovered so far.

Immune Suppression
Various experiments with organisms in space and tests of astronaut’s blood cells have indicated that the immune system may change when exposed to microgravity (weightlessness). Immune suppression is the altered ability of immune system cells to respond to stimulation. The result is that the cells no longer function properly and cannot do their job of keeping the body healthy by fighting microorganisms.

Virulence changes in bacteria
There is evidence that some microorganisms also change in space. Some bacteria seem to become more virulent (disease-causing) after growing in microgravity.

A suppressed immune system exposed to organisms that have become more virulent is a very bad combination!
More experiments are needed to examine these questions to understand how and why this happens. Scientists need to understand more about immune suppression in space and the changes that space exposure causes in bacteria and other microorganisms in order to make sure that astronauts can live safely in space for long periods.

Organisms such as Drosophila provide an effective tool for understanding the changes that lead to immune suppression in space.
Drosophila’s immune system can be studied in space to investigate whether the innate immune responses become suppressed. Bacteria and fungi can be exposed to microgravity then studied in a ground laboratory to investigate whether they have become more virulent or not. This can be done by infecting Drosophila with the space-flown bacteria and fungi and running tests to check the immune response.

Healthy Astronaut Leroy Chiao, Expedition 10 commander and NASA ISS science officer, participates in extravehicular activities (EVA) performed during Expedition 10.Next steps
Once we fully understand how the immune response and bacterial virulence change as a result of spaceflight, we will try to develop countermeasures to these effects. One countermeasure may be exercise, since exercise is known to keep humans healthy on Earth!

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 FirstGov  NASA
Editor: Carol Elland
NASA Official: B J Navarro
Last Updated: September 2006
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