While humankind aims for manned missions to the Moon and Mars, a new study showed that T-cells of the immune system can get affected by weightlessness in space and render them ineffective to fight infections.

Space is an extremely hostile environment that poses threats to human health. One such threat is changes to the immune system that occur in astronauts while in space and that persist after their return to Earth, said researchers in the study, published in the journal Science Advances. This immune deficiency can leave them more vulnerable to infection and lead to the reactivation of latent viruses in the body.