in microgravity, also did not change. Although the total number of WBCs increased significantly
upon landing, the overall population of T and B lymphocytes did not change appreciably after
long-duration spaceflights. However, T-lymphocyte function was decreased, which supports
previous observations and recently confirmed from a study of 12 Russian cosmonauts after
long-duration missions. Researchers proposed that a long-duration spaceflight, perhaps
coupled with several extravehicular activities (EVA), activated and suppressed T-lymphocytes’
response to proliferate, thus resulted in an immune deficit against potential infections. The
investigation also showed gross individual differences in concentration of cytokines before
launch possibly due to preflight stress. The random changes after short- and long-term missions
suggest that cytokines may be highly sensitivity to the factors associated with re-entry and
readaptation to Earth’s gravity. Also, a decrease in natural killer (NK) cells population and
activity in the long-duration crew members may be an indication of a weakened immune
system, plus the reduced NK activity in some subjects on the first day after short-duration could
very well be an acute response to landing stress.
Many improvements have been made to the living conditions of orbital vehicles and the scope
of spaceflight immunological research expanded since the first human was flown into space 50
years ago. However, ISS crew members still exhibit negative shifts in the immune system during
initial readaptation to gravity. Such alterations, scientists suspect, could lead to compromised
defenses against infections by limiting the immune system’s communicating and disease
fighting capabilities. In light of these results, full characterization of all aspects of the innate and
adaptive immune system after prolonged and brief flights appears essential for understanding
the relationship of microgravity and stress effects of spaceflight on human space explorers.
PUBLICATION(S)
Choukèr A. Stress challenges and immunity in space. 2012. ISBN 978-3-642-22271-9 e-ISBN 978-
3-642-22272-6 doi 10.1007/978-3-642-22272-6.
Strewe C, Feuerecker M, Nichiporuk IA, et al. Effects of parabolic flight and spaceflight on the
endocannabinoid system in humans. Reviews in the Neurosciences. September 2012;23(5-
6):673-680. doi: 10.1515/revneuro-2012-0057.
Morukov BV, Rykova MP, Antropova EN, Berendeeva T, Ponomaryov S, Larina IM. T-cell
immunity and cytokine production in cosmonauts after long-duration space flights. Acta
Astronautica. 2011;68:739-746. doi: 10.1016/j.actaastro.2010.08.036.
Rykova MP, Antropova EN, Larina IM, Morukov BV. Humoral and cellular immunity in
cosmonauts after the ISS mission. Acta Astronautica. 2008;63:697-705. doi: 10.1016/
j.actaastro.2008.03.016.
This investigation is complete; however additional results are pending publication.