How does space affect astronauts’ immune systems?

Writer Samira Joineau
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Space exploration has captivated human imagination for decades, but the challenges associated with extended periods of time in microgravity are profound and wide-ranging. One of the most crucial yet lesser-known aspects affected by space travel is the human immune system.

As astronauts venture beyond our planet, their immune systems undergo complex changes that can impact their health and well-being. In this sense, researchers at Karolinska Institutet have examined how T cells of the immune system are affected by weightlessness. The results of their study could help explain why astronauts’ T cells become less active and less effective when it comes to fighting infection.

T cells, as well as natural killer (NK) cells, are vital components of the immune response. They play a crucial role in identifying and destroying infected and cancerous cells. In space, the functioning of these cells are compromised: this altered environment can lead to reduced T cell activity. In consequence, it potentially leaves astronauts more susceptible to infections. 

If astronauts are to be able to undergo safe space missions, we need to understand how their immune systems are affected and try to find ways to counter harmful changes to it”, Lisa Westerberg, principal researcher at the Department of Microbiology, Tumor & Cell Biology, explained. 

In the study, the involved researchers have tried to simulate weightlessness in space using a method called dry immersion. The latter refers to a custom-made waterbed that tricks the body into thinking it is in a weightless state. 

To do this, the researchers examined T cells in the blood of eight healthy individuals for three weeks of exposure to simulated weightlessness. To note that the participants performed blood analyses before the experiment; and then 7, 14, and 21 days after the start, and at 7 days after the end of the experiment. 

The results show that significant changes occur after 14 days. Carlos Gallardo Dodd, PhD student at the Department of Microbiology, Tumor & Cell Biology at Karolinska Institutet, noted that “The T cells began to resemble more so-called naïve T cells, which have not yet encountered any intruders”. 

This could mean that they take longer to be activated and thus become less effective at fighting tumor cells and infections”, he further stated. These results can hence support the development of new treatments which could help reverse these changes to the immune cells’ genetic program. 

Besides, the researchers noticed that the T cells had “adapted” their gene expression to weightlessness after 21 days, meaning they almost returned to their original state. Yet, 7 days after the end of the experiment, results showed that cells had regained some of the changes. 

The researchers now plan to use Esrange Space Centre’s sounding rocket platform in Kiruna, Sweden, to study how T cells behave in weightless conditions and how their function is affected.