Researchers explore how the immune system goes awry during space travel and the implications for human aging on Earth

As long as humans have been traveling into space, astronauts have experienced significant health effects from the extreme conditions of space flight, notably the reduction of gravity.

Two Buck scientists led a team that has revealed for the first time how the lack of gravity affects the cells of the immune system at single cell resolution. The co-senior authors, along with Christopher E. Mason, Ph.D. of Weill Cornell Medical College, Associate Professor David Furman, Ph.D. and Associate Professor Daniel Winer, MD, have published an extensive survey of how gravity affects immune cells, and the identification of "space nutraceuticals" to counter aberrant effects of microgravity on these cells. The work is published in Nature Communications

"We show how simulated microgravity shapes immune cells and how the changes in force alter the cells' function at the single cell level," said Winer. "This level of resolution is new and exciting in understanding the effects of microgravity on cells."

Using cells in simulated microgravity, combined with data from space flight from astronauts and mice on the International Space Station, the researchers created a complete picture of how the different cells of the immune system in the peripheral blood are shaped by reduced gravity. These cells include lymphocytes and monocytes, which are the main players in immunity.

The study has potential implications for immune aging on Earth since the changes observed during aging resemble those captured during space travel.

The team additionally outlines a pathway for identifying compounds that can reverse the effects of near zero gravity, and demonstrates that one of the compounds, quercetin, shows promise for mitigating the damage caused by spaceflight and during normal aging on the ground.

"Our work provides a resource to better understand how and why the immune system changes in simulated microgravity and spaceflight," said Furman. "We also provide a way to develop countermeasures to maintain normal immunity under these harsh conditions."

Astronauts in low Earth orbit, such as on the International Space Station, suffer from immune system problems, especially infections, latent viruses reactivating, and skin sensitivity. These reactions occur even on short-term spaceflights.

Previous studies using actual or simulated microgravity conditions have found impaired function of various immune cells. However, the fundamental mechanisms, genes, and pathways that explain immune dysfunction in microgravity were mostly unclear, the researchers said. They wanted to understand what was happening on a cellular level to explain the changes.

The team, led by the study's co-first authors Buck postdoctoral researcher Fei Wu, Ph.D. and graduate student Huixun Du, examined in depth how 25 hours of simulated microgravity affects the human peripheral blood mononuclear immune system, using samples from 27 healthy human donors between the ages of 20 and 46.

To simulate an environment with almost no gravity, the team grew the cells inside of a Rotating Wall Vessel, a device developed by NASA to simulate microgravity conditions.