Where No One Can Hear You Sneeze

Space is a bad place to be sick:

As far as space dangers go, illness doesn’t get much attention, which is kinda strange given that one of the most distinct effects of microgravity on the human body are tanking immune systems. A 2012 piece in Time reports, “the immune system can go on the fritz in space: wounds heal more slowly; infection-fighting T-cells send signals less efficiently; bone marrow replenishes itself less effectively; killer cells— another key immune system player—fight less energetically.” Meanwhile, many pathogens have an awesome time in space, growing stronger and increasing their resistance to antimicrobials. In particular, both herpes and staph have been shown to thrive in the gravity-free, hyper-sterile environment of a space vessel.

A study out this week examining space-born Drosophila flies—often studied because of the similarity between the flies’ immune systems and that of humans—found that in the case of fungal infections, microgravity effectively nullified the immune response.

How the study worked:

To figure out why the space flies had trouble with the fungus, the scientists analyzed all of the flies’ genes. Both the space flies and the Earth flies were born with the same genes, but exactly which of those genes turned on and went to work differed between them. In Earth flies, the genes associated with their immune systems kicked into high gear after they got infected with the fungus. Among other genes, Earth flies activated something called the Toll signaling pathway, which scientists have long known flies use to fight off fungi. Humans have Toll-like genes, too, and they also work in immunity.

The space flies reacted differently from their stay-at-home siblings. They turned on some immunity genes after encountering Beauveria bassiana, so it’s not like they were totally helpless. But they didn’t use all of the genes the Earth flies used, and they didn’t turn up their Toll pathway genes. In their paper, the biologists called their spacefaring flies “severely immunocompromised.” Strangely, when the biologists raised flies in a centrifuge to simulate higher-than-Earth gravity, they were more likely to survive a fungal infection than normal Earth flies.