Details for Merel Van Walleghem

Researchgroup Cell Systems & Imaging
Function Former member
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Consequences of space stressors on immunity: evaluation of immunological changes using in vitro space analogs on Earth.

During space flight astronauts are exposed to both physical (radiation and microgravity) and psychological stress factors that can result in detrimental health effects. In-flight and earth-based studies have shown that these space stressors can induce a weakening of the immune system. The immune system is a complex network of organs, tissues and cells that protects the body against foreign substances and microorganisms. The functions of the different immune cells are mediated by cytokines, soluble proteins used to transmit messages from cell to cell.


Although research clearly indicates the adverse effect of space stressors on human health, there is much more to learn about the impact of these factors, alone or in combination, on the immune system and their underlying mechanisms of action. In response to the call for ‘Life Science Research onboard the International Space Station (ISS)’, two space flight studies were accepted by the European Space Agency (ESA). The aim of these studies is to monitor the astronauts’ immunity during long-term space flight.


This PhD project is part of the ground-based preparation for the ESA project on monitoring cellular immunity on the ISS. In this study, the impact of radiation and microgravity on cellular immune functions ex vivo of the astronauts onboard the ISS and its potential modulation through stress hormones will be investigated. In order to perform in vitro space studies on Earth, space conditions need to be simulated on ground. Although these conditions can not completely be recreated on Earth, good model systems are available. Cosmic radiation can be simulated by combined exposure of the samples to low and high-energy radiation. For in vitro experiments, microgravity can be simulated within the Random Positioning Machine (RPM). This device randomizes in three dimensions the direction component of the gravity vector in order to obtain, on average, a net force close to zero as the sample is taken as a reference. Psychological stress can be simulated by the addition of stress hormones.


The overall goal of the PhD research is to evaluate how (simulated) space flight stressors can affect the adaptive immune system, and more specifically the cell-mediated immunity. Using the in vitro delayed-type hypersensitivity (DTH) assay, the impact of the simulated space stressors on the cellular immune response against recall antigens will be evaluated. Human blood samples will be exposed to different challenges (e.g. bacterial/viral/fungal antigens, pokeweed mitogen) in combination with one or multiple space-simulated conditions. After incubation, the levels of cytokines released in the supernatant by the immune cells in response to the specific stimulus will be measured by the Luminex technology. Since changes in cytokine concentrations mirror the degree of the cellular immune response, the obtained data will provide information how different space stressors can affect the immune response. To identify the underlying molecular mechanisms whereby the different stressors induce changes in the adaptive immune system, gene expression analysis will be performed by microarray and quantitative RT-PCR.


In view of the extended duration missions (e.g. to Mars), there is an urgent need to develop safe and effective countermeasures to prevent, mitigate and/or treat the harmful consequences of space environments. Based on the results of the in vitro DTH assay and gene expression analysis, possible candidates can be selected in the fields of radiation, microgravity and mental stress. The ability of these potential countermeasures to interfere with the space stressor-induced immune changes will be subsequently tested in the set-up.


The obtained knowledge will contribute to maintain the astronauts’ health in space, as well as improve our understanding of the normal immune response and immunosuppressed conditions on Earth.