Plasma Cytokine Concentrations Indicate In-vivo Hormonal Regulation of Immunity is Altered During Long-Duration Spaceflight

Abstract

Background: Aspects of immune system dysregulation associated with longduration spaceflight have yet to be fully characterized, and may represent a clinical risk to crewmembers during deep space missions. Plasma cytokine concentration may serve as an indicator of in vivo physiological changes or immune system mobilization. Methods: The plasma concentrations of 22 cytokines were monitored in 28 astronauts during longduration spaceflight onboard the International Space Station. Blood samples were collected three times before flight, 35 times during flight (depending on mission duration), at landing and 30 days postlanding. Analysis was performed by bead array immunoassay. Results: With few exceptions, minimal detectable mean plasma levels (<10 pg/ml) were observed at baseline (launch minus 180) for innate inflammatory cytokines or adaptive regulatory cytokines, however IL1ra and several chemokines were constitutively present. An increase in the plasma concentration IL8, IL1ra, Tpo, CCL4, CXCL5, TNF(alpha), GMCSF and VEGF was observed associated with spaceflight. Significant postflight increases were observed for IL6 and CCL2. No significant alterations were observed during or following spaceflight for adaptive/Tregulatory cytokines (IL2, IFN(gamma), IL17, IL4, IL5, IL10). Conclusions: This pattern of cytokine dysregulation suggests multiple physiological adaptations persist during flight, including inflammation, leukocyte recruitment, angiogenesis and thrombocyte regulation