In April 2013, 45 pioneering mice were launched into space as part of the Bion-M1 mission, boldly going where few mice had gone before. But when these voyagers returned, scientists found that space had left its mark on the mice, who spent 30 days hurtling around in low-Earth orbit. Their immune systems were pretty messed up, and unfortunately, this likely happens to humans, too.

Since the mice returned in May 2013, Fabrice Bertile, Ph.D., has been analyzing the way that their journey impacted the immune systems of six of the original 45 at the Hubert Curien Multidisciplinary Institute in France. His findings, published today in The FASEB Journal don’t bode well for astronauts looking to replicate their mission: Extended time in microgravity seems to decrease the production of key cells in the immune system called B lymphocytes — white blood cells that help the body identify potential infectious invaders and take action against them. Bertile tells Inverse that the idea that space handicaps our immune systems fits well with earlier findings, some of which are even on humans.

bion m1
The rocket containing Bion-M1 which carried mice and newts into space for a month.

“Impairment of the immune system therefore appears [to be] a common feature of the response to weightlessness in all organisms,” Bertile says. “In the framework of the envisioned deep space missions to Mars, the moon, or an asteroid that will require very long duration flights, the risk will increase and we need be prepared beforehand.”

One week after the mice returned, he found that the mice who went to space had 61 percent fewer B lymphocytes in their spleens compared to Earth-bound controls and 41 percent fewer B lymphocytes in their bone marrow. This dearth of B lymphocytes, Bertile says, provides insight into a pattern we’ve already seen in human astronauts.

He points to a 2016 study on 46 astronauts who spent six months aboard the International Space Station. In that scenario, nearly half of the subjects struggled to fight off common infections like fever, fungal infection, flu-like illness, urinary tract infections, and other viral diseases. Given this finding and others like it, NASA is already aware that microgravity seems to take its toll on health, but Bertile adds that we need to pursue every line of inquiry into this, especially now that humanity is on the verge of longer space missions.

Previous work has shown that certain microbes actually become more virulent in space — which is alarming since scientists recently announced that the ISS is home to several types of toilet microbes that posses antibiotic resistance genes. Bertile argues that his new study broadens the way scientists have approached this issue by specifically looking at the B lymphocytes.

mice in microgravity
Not all mice keep their cool in microgravity, which the Air Force learned in 1953. 

“Until our work, most studies had addressed the effects of spaceflight on innate immunity, while lymphocytes B cells had been less investigated,” he says. “This suggests that even if the bone and immune function have mainly been investigated separately up to now, getting information on bone interconnections with the immune system should be envisioned in future studies.”

The cells Bertile investigated fit into a subset of the immune system called the adaptive immune system. At the outset of infection, B lymphocytes help the body produce antibodies, which can fight the infection. But some of these cells actually help the body remember these infections and will reactivate a quicker immune response the next time they encounter the same pathogen. Bertile wanted to hone in on B cells found in bone marrow because he believes that there’s a connection between bone-loss caused by microgravity — a well-established phenomenon — and the immune system changes that put astronauts at risk.

With this in mind, he believes his work could inform how we think about preventing illness during spaceflight. He argues that space agencies should focus on restoring human immune systems to full capacity, as well as trying to hard to prevent infections in the first place.

“In close collaboration with people from the French Space Agency (CNES), I think that succeeding in maintaining a functional immune system in space would be safer than only trying to avoid infections (e.g. preflight vaccination program; routine cleaning with a germicidal wipe; hand-hygiene compliance) or fight occurring infections,” Bertile adds.