Gravity-Related Immunological Changes in Human Whole Blood Cultured Under Simulated Microgravity Using an In Vitro Cytokine Release Assay

Abstract

Although immune dysfunction by space conditions has been reported postflight, as well as during ground-based experiments, the cause(s) and nature of the immunological changes are not completely understood. Microgravity has been suggested as one of the factors responsible for the observed immune dysregulation. The goal of this study was to assess immune changes in simulated microgravity (s-μG) using an in vitro cytokine release assay. The effect of s-μG provided by the desktop random positioning machine on cell-mediated immunity was examined by analyzing interleukin 2 (IL-2), interferon-γ (IFN-γ), tumor necrosis factor alpha (TNF-α), and interleukin 10 (IL-10), in response to immune cell stimulation in whole blood samples (n = 10). Stimuli used were bacterial recall antigens, pokeweed mitogen (PWM), lipopolysaccharide (LPS), or heat-killed Listeria monocytogenes (HKLM). S-μG caused an overall inhibition of the IL-2 and IFN-γ responses to recall antigen and mitogen stimulation. More specifically, s-μG most strongly influenced the levels of all four cytokines elicited by bacterial recall antigen stimulation. In contrast, HKLM-induced TNF-α secretion was elevated. The average concentrations of TNF-α in response to PWM and LPS and IL-10 release stimulated by PWM, LPS, and HKLM were not significantly altered by s-μG. However, a variable response between individual subjects could be observed. In conclusion, our results demonstrate that the in vitro cytokine release assay can detect gravity-related immune alterations. Furthermore, the use of multiple stimuli and the associated changes in cytokine secretion has the potential to reveal information on the underlying mechanisms affected by s-μG.

Immunological Changes During Space Travel: A Ground-Based Evaluation of the Impact of Neutron Dose Rate on Plasma Cytokine Levels in Human Whole Blood Cultures

“…Basal IL-2 and IFN-γ concentrations were below the assay detection limit, indicating that the study population was indeed healthy and there was no sign of infection [56]. In a previous study, IL-2 secretion was only increased for 50% of the subjects after exposure to LPS [22]. We observed an increase for only 25% of the donors after LPS stimulation.…”

“…The in vitro cytokine release assay is a modified version of the methods described by Feuerecker et al [51] and Van Walleghem et al [22]. Post-exposure, irradiated whole blood was distributed equally amongst culture tubes and diluted 1 to 1 in 750 µl Roswell Park Memorial Institute (RPMI) medium (Gibco, Massachusetts, USA), supplemented with 10% foetal calf serum (Lonza, Basel, Switzerland), 1% penicillin and streptomycin (Lonza), with-or-without an immune cell stimulant, in sterile 2.0 ml cryovials.…”

“…Terrestrial spaceflight analogues are a more accessible alternative to study spaceflight-related health effects, their causative factors and to test potential countermeasures [21]. For example, several ground-based studies could clearly demonstrate the dramatic impact of microgravity on the immune system [21][22][23][24][25][26][27][28]. However, during space travel, radiation and psychological stress factors (e.g., isolation, sleep deprivation, and heavy workload) may have a significant synergistic or antagonistic effect on human immunity [29,30].…”

Cells´ Flow and Immune Cell Priming under alternating g-forces in Parabolic Flight

“…In the second part of the study, we investigated antigen-induced immune cell activation after acute gravitational stress by PF. For this, we performed whole blood ( delayed type hypersensitivity (DTH)-) assays employing the bacterial antigens LPS and HKLM, which are ligands for TLR4 and 2, and PWM, which induces activation and mitosis in lymphocytes 31 .…”

Synergistic Effects of Weightlessness, Isoproterenol, and Radiation on DNA Damage Response and Cytokine Production in Immune Cells

“…Cytokine production in response to low-dose/low-dose rate (Co γ-rays 0.01 Gy, 0.03 cGy/h), with and without acute 2 Gy proton (1 Gy/min) or γ-ray (0.9 Gy/min) irradiation has been investigated also, concluding that the release of at least some cytokines in response to acute 2 Gy radiation is dependent on the radiation quality at the time of assessment, and on the pre-exposure to low-dose radiation with γ-rays [ 78 ]. Isoproterenol suppresses release of cytokines from concanavalin A-activated T cells [ 79 ], and microgravity-induced changes in cytokine release have been reported recently in mitogen-stimulated cells [ 80 ]. However, radiation-induced cytokine production under microgravity conditions has not been investigated.…”