npj Microgravity Article: Alterations in adaptive immunity persist during long-duration spaceflight
This article by Brian Crucian and Duane Pierson (NASA Johnson Space Center, Houston, TX, USA), Raymond P Stowe (Microgen Laboratories, La Marque, TX, USA), Satish Mehta (Enterprise Advisory Services, Inc., Houston, TX, USA), Heather Quiriarte (JES Tech, Houston, TX, USA) and Clarence Sams (Space and Clinical Operations Division, Houston, TX, USA) was published online by npj Microgravity on September 3, 2015.
It is currently unknown whether immune system alterations persist during long-duration spaceflight. In this study various adaptive immune parameters were assessed in astronauts at three intervals during 6-month spaceflight on board the International Space Station (ISS).
To assess phenotypic and functional immune system alterations in astronauts participating in 6-month orbital spaceflight.
Blood was collected before, during, and after flight from 23 astronauts participating in 6-month ISS expeditions. In-flight samples were returned to Earth within 48 h of collection for immediate analysis. Assays included peripheral leukocyte distribution, T-cell function, virus-specific immunity, and mitogen-stimulated cytokine production profiles.
Redistribution of leukocyte subsets occurred during flight, including an elevated white blood cell (WBC) count and alterations in CD8+ T-cell maturation. A reduction in general T-cell function (both CD4+ and CD8+) persisted for the duration of the 6-month spaceflights, with differential responses between mitogens suggesting an activation threshold shift. The percentage of CD4+ T cells capable of producing IL-2 was depressed after landing. Significant reductions in mitogen-stimulated production of IFNγ, IL-10, IL-5, TNFα, and IL-6 persisted during spaceflight. Following lipopolysaccharide (LPS) stimulation, production of IL-10 was reduced, whereas IL-8 production was increased during flight.
The data indicated that immune alterations persist during long-duration spaceflight. This phenomenon, in the absence of appropriate countermeasures, has the potential to increase specific clinical risks for crewmembers during exploration-class deep space missions.