Immune Dysfunction in Spaceflight: An Integrative View

Physical or psychological stress in space is one of the major concerns for the health of space travelers. The critical stress factors, especially during long-duration spaceflight missions, consist of stressors caused by prolonged isolation, ecologically and environmentally closed systems, microgravity, radiation, workload, and circadian misalignment. These conditions collectively can provoke an allostatic load and overload resulting in an imbalance of cellular and organ functions, including immune dysfunction. To understand the adaptation of the immune system to spaceflight conditions, investigations of animals and humans in spaceflight have been conducted on the ISS and on Earth (with spaceflight analogues). The knowledge gathered on alterations in immune homeostasis resulting from the multiple stressors in space and the new mechanistic insights provided by analogue investigations on Earth are prerequisite for defining appropriate, safe, and efficient countermeasures to mitigate immune related health problems, especially in light of planned manned exploration class missions.