Why does spaceflight impair the immune system?

Tregs also play a role in resistance to infections, allergy sensitivities, immune memory, and transplantation tolerance, in which the immune system does not attack transplanted tissue.The current study’s findings indicate that space travel activates Tregs earlier, thereby damping down the immune system before the threat has been cleared.The scientists exposed blood samples from eight healthy adult participants to simulated microgravity.They loaded the samples into a machine developed by the National Aeronautics and Space Administration (NASA), called the Rotating Wall Vessel, exposing the samples to 18 hours of either 1-gravity, which is the amount of gravity experienced on Earth, or microgravity.Using a novel single-cell analysis, the researchers could pinpoint individual immune cells by type in order to detect and tally proteins involved in immune function.This study offers greater insight into the cellular interactions that explain microgravity’s immunosuppressive effects.According to the researchers, the lack of gravity seems to set off a multicellular response that may lower resistance to pathogens.Surprisingly, when the team stimulated an immune response in the blood samples with two molecules that mimicked a pathogen, the Tregs dampened the resulting immune response before it had time to respond to the threat.The study authors report: “Our data indicate that exposure to [microgravity] results in the broad inhibition of immune cell capacity to respond to a potent activating stimulus […] and are consistent with transcriptomic previous analyses of human immune cells exposed to the spaceflight environment.”Dr. Gaudilliere calls this a “double whammy” of “a dampening of T lymphocyte immune activation responses — but also an exacerbation of immunosuppressive responses by Tregs.” T lymphocytes, which are also called T cells, play a central role in the body’s response to pathogens.