Page 149 - Helicobacter pylori and Gastric Cancer: From Tumor microenvironment to Immunotherapy

Purpose and structure of this review
Spaceflight causes deregulation of the human immune system and may compromise a crews wellbeing as during missions their health is continuously challenged by environmental conditions. Consequently, it is crucial to comprehend the biology of immune modulation under spaceflight circumstances possibly providing us with a means to uphold immune homeostasis under such conditions[17]. Life in the sterile and confined surroundings of a spacecraft in the presence of microgravity and cosmic radiation may alter the equilibrium between the human body and the microbiome. The combination of a deregulated immune system and an altered microbiome increase the risk of microbial infection and potentially the development of conditions related to reduced tolerance. This risk is further heightened by an increase in virulence of pathogens in microgravity. Health status of astronauts might potentially benefit from maintaining a healthy microbiome by specifically managing their diet on space in addition to probiotic therapies. This review focuses on the current knowledge/understanding of how spaceflight affects human immunity and microbiome[18]. Some of the impact on immune function certainly relate to psychological factors (cosmonauts can be expected to suffer from stress, wearing working schedules and anxiety), disturbance of circadian rhythms, environmental exposure to cosmic radiation and magnetic fields and substantial ergonomic discomfort (cramped conditions, inadequate lifestyle and nutritional regimen etc.)[15, 19]. However, there are good reasons to assume that the weightlessness itself negatively influences immune competence of the human body. Experimentation with crew members of the Apollo and Soyuz missions[20] showed reduced reactivity of peripheral blood lymphoid cells. And a landmark experiment conducted in Spacelab 1 in 1983 demonstrated a near absent activation of peripheral blood leukocytes upon exposure to concanavalin A (Con-A) when compared to identical ground controls[21]. This observation sparked wide-spread interest into microgravity effects on the immune system. Although this original view has been confirmed in elegantly designed experiments in which controls were incubated in an in-flight 1×g reference centrifuge[22], many of the details as to how gravity and immune cell function interact remain obscure.
In this review we shall look at the different levels at which microgravity might interact with the human immune system and analysing the available evidence, we shall conclude that especially T cell[15, 21-24] and Natural Killer cell responses are negatively influenced[14-16, 19], but that innate immunity and especially granulocyte
Health from above?
Health from above?
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