Immune System Dysregulation Occurs During Short Duration Spaceflight On Board the Space Shuttle

Background Post-flight data suggests immunity is dysregulated immediately following spaceflight, however this data may be influenced by the stress effects of high-G entry and readaptation to terrestrial gravity. It is unknown if immunity is altered during spaceflight. Methods Blood samples were collected from 19 US Astronauts onboard the Space Shuttle similar to 24 h prior to landing and returned for terrestrial analysis. Assays consisted of leukocyte distribution, T cell blastogenesis and cytokine production profiles. Results Most bulk leukocyte subsets (WBC, differential, lymphocyte subsets) were unaltered during spaceflight, but were altered following landing. CD8+ T cell subsets, including cytotoxic, central memory and senescent were altered during spaceflight. T cell early blastogenesis varied by culture mitogen. Functional responses to staphylococcal enterotoxin were reduced during and following spaceflight, whereas response to anti-CD3/28 antibodies was elevated post-flight. The level of virus specific T cells were generally unaltered, however virus specific T cell function was depressed both during and following flight. Plasma levels of IFN alpha, IFN gamma, IL-1 beta, IL-4, IL-10, IL-12, and TNF alpha were significantly elevated in-flight, while IL-6 was significantly elevated at R+0. Cytokine production profiles following mitogenic stimulation were significantly altered both during, and following spaceflight. Specifically, production of IFN gamma, IL-17 and IL-10 were reduced, but production of TNF alpha and IL-8 were elevated during spaceflight. Conclusions This study indicates that specific parameters among leukocyte distribution, T cell function and cytokine production profiles are altered during flight. These findings distinguish in-flight dysregulation from stress-related alterations observed immediately following landing.