Alterations in adaptive immunity persist during long-duration spaceflight

Abstract

Background: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).AIMS:To assess phenotypic and functional immune system alterations in astronauts participating in 6-month orbital spaceflight.Methods: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.Results: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.Conclusions: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.

Long-Term Microgravity Effects on Isometric Handgrip and Precision Pinch Force with Visual and Proprioceptive Feedback

“…Our results are in accordance with previous NASA studies that demonstrate International Journal of Aerospace Engineering that even bones are affected over the course of long-term missions by loss of their total hip bone mass [14]. Moreover, our data add information to the list of known effects of space flights on the human body during long-duration missions such as muscle atrophy, bone demineralization, altered immune function [15,16], cardiovascular system dysfunction [17,18], and also alterations in sleep function [19]. A significant amount of data on the decrease in the performance of various groups of muscles has been collected from astronauts flying from 1989 to 1995 in NASA's orbiters or Russian capsules [20].…”

Incidence of clinical symptoms during long-duration orbital spaceflight

“…It is also interesting that the highest concentration of reported events occurred early within the 6-month mission durations. While the slope of immune alterations during spaceflight is still largely unknown, the literature to date generally finds that alterations persist for the duration of a 6-month orbital spaceflight 25. We anticipate upcoming investigations on board the ISS will shed further light on the complexities of immune adaptation during flight, and planned 1-year mission durations will improve our understanding regarding the kinetics of these alterations.…”

“…Humoral immunity may also be affected by spaceflight, as animal studies have indicated that the somatic hypermutation process responsible for diversification of antibody binding sites was reduced during spaceflight 23. Recent data collected on board the Space Shuttle and International Space Station (ISS) confirms that human immune dysregulation is indeed an in-flight phenomenon, and not merely a post-flight stress response to landing and readaptation following deconditioning 24,25…”

Changes in mitochondrial homeostasis and redox status in astronauts following long stays in space

“…Temperature, carbon dioxide levels and humidity are well controlled in space shuttles5657. A project examining immune parameters, i.e., peripheral leukocyte distribution, T-cell function, virus-specific immunity, and mitogen-stimulated cytokine production profiles, in twenty-three astronauts revealed that the immune alterations persist during long-duration (6 month) spaceflights58. Immune alterations are likely to be critical factors in the changes in homeostasis occurring in astronauts.…”