Abstract
Gravitational stress in general and microgravity (µg) in particular are regarded as major stress factors responsible for immune system dysfunction in space. To assess the effects of alternating µg and hypergravity (hyper-g) on immune cells, the attachment of peripheral blood mononuclear cells (PBMCs) to adhesion molecules under flow conditions and the antigen-induced immune activation in whole blood were investigated in parabolic flight (PF). In contrast to hyper-g (1.8 g) and control conditions (1 g), flow and rolling speed of PBMCs were moderately accelerated during µg-periods which were accompanied by a clear reduction in rolling rate. Whole blood analyses revealed a “primed” state of monocytes after PF with potentiated antigen-induced pro-inflammatory cytokine responses. At the same time, concentrations of anti-inflammatory cytokines were increased and monocytes displayed a surface molecule pattern that indicated immunosuppression. The results suggest an immunologic counterbalance to avoid disproportionate immune responses. Understanding the interrelation of immune system impairing and enhancing effects under different gravitational conditions may support the design of countermeasures to mitigate immune deficiencies in space.
Highlights
It is almost six decades ago, that the first human was sent to space
Cell number counts for all gravity conditions showed comparable levels
Decreased rolling rate in μg was accompanied by a mild increase in average cell rolling speed (185 ± 47 μm/sec.) compared to control and hyper-g, which all showed similar velocities (1 g: 139 ± 34 μm/sec., ground control: 153 ± 33 μm/sec., hyper-g: 142 ± 41 and 152 ± 47 μm/sec)
Summary
Driven by political and technological prestige, curiosity and the desire of expanding knowledge about Earth and our solar system, human space flight nowadays maintains an important role in exploring the biology of life, the gravitational pull, and the lack thereof. Another main task of space research is to assess the feasibility of long-term manned deep space missions, such as travelling to Mars. A reduced expression of surface-bound molecules like intercellular adhesion molecule 1 (ICAM1) is thought to contribute to impaired cell migration and activation of cells from both the innate and adaptive immune system[14]. Permanent remodelling of the cytoskeleton by alternating μg and hyper-g conditions has an effect on cell mechanical stability[19,20], motility and adhesion[21] and cell signalling[11]
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