Fifteen of 29 Apollo crewmembers had difficulty with infections during and immediately after return from spaceflight, with one member of the Apollo 13 mission developing a serious urinary tract infection during the flight.
Problems with infection at the time of spaceflight have yielded one of the more effective countermeasures to prevent detrimental effects of spaceflight on human health. It is possible that the changes in immune responses induced by spaceflight could have contributed to decreased resistance to infection. Astronauts are now subject to a crew health stabilisation programme, which limits interactions with the public immediately before and after flight. This has limited the occurrence of infections during spaceflight missions.
Former ESA astronaut Claudie Haigneré before
launch of the Andromède mission in October 2001.
Strict pre-flight procedures including quarantine
helps reduce the possibility of astronauts contracting
infections during missions. (Image: ESA/CNES)
Exposure of humans to spaceflight conditions results in changes in immune responses. Alterations in the regulation of immunity could have profound effects on the ability to resist infection and the development of tumours. Among the changes are alterations in the production of substances used for communication between cells to generate immune responses (proteins known as cytokines), the production of white blood cells, and the functioning of natural killer cells, which target and destroy dangerous or infected cells. The contribution of these changes in the immune system to alterations in resistance to infection and tumours remains to be fully established.
Constituents of blood. L is a lymphocyte or white blood
cell, which play an important part in the body’s
immune system. E is an erythrocyte or red blood cell
and P is a blood platelet. (Image: NASA)
Current spaceflight conditions include occupation of the International Space Station in low Earth orbit for extended periods of time. Future plans could include possible human exploratory missions to the Moon and Mars. During extended deep spaceflights, astronauts will be exposed to chronic radiation that could influence the immune system.
Studies on the immune system have been carried out on cell cultures, animals, and humans in space and in environments that model some spaceflight conditions such as bed rest studies. Results utilising the head-down tilt bed rest model to study the effects of spaceflight conditions on the immune system are limited, but show a pattern similar to the results observed when humans are exposed to space. The bed rest model has been established as valid for studying the effects of spaceflight conditions on certain immune responses such as production of substances used for communication between cells, but all of the studies to date have been carried out on men. The proposed study is designed to determine the effects of bed rest on immune responses of women.
The two-month bed rest period will allow for changes in muscle and bone similar to those observed during longer-term spaceflight. This length of time will also allow for changes in the immune system similar to those observed during longer-term spaceflight.
What is it good for?
The overall hypothesis to be tested is that female subjects subjected to the bed rest period will experience a suppression of immune responses and enhanced susceptibility to infection. By carrying out these studies, the effects of bed rest on immune function and control of viral infections will be correlated.
The overall hypothesis to be tested is that female subjects subjected to the bed rest period will experience a suppression of immune responses and enhanced susceptibility to infection. By carrying out these studies, the effects of bed rest on immune function and control of viral infections will be correlated.
It is expected that there will be a depression of the immune system, including the levels of cytokines and antibodies. It is also expected to determine if the immune system factors studied will be positively or negatively affected by the use of the countermeasures of combined exercise or nutritional supplements. Primarily these countermeasures will be applied to protect mass and function of the volunteers’ muscles and bones. Their effect on other systems of the human body is also of great interest. The results of this proposed study will aid in our basic understanding of the effects of the simulated spaceflight environment on the immune system and resistance to infection. In addition, the results will help in planning future spaceflight missions and contribute to the design of appropriate countermeasures for the effects of spaceflight conditions on muscle, bone and immunity.
How is it done?
Effects of bed rest on immune responses: This will be determined by examining the effects of bed rest on immunisation to a bacterial virus (phiX174), which is harmless to humans, and production of white blood cells and cytokines.
Effects of bed rest on immune responses: This will be determined by examining the effects of bed rest on immunisation to a bacterial virus (phiX174), which is harmless to humans, and production of white blood cells and cytokines.
Effects of bed rest on resistance to infection: This will be determined by examining the effects of bed rest on reactivation of persistent virus infections with which the subjects are already infected, including the Epstein-Barr virus and human polyomaviruses.
The effect of the applied countermeasures during the long-term bed rest on immune responses and resistance to infection will be determined from analysis of saliva, urine and blood samples.
Microscopic image of the Epstein-Barr virus, a harmless virus
with which volunteers will be infected (Image: NASA)
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