Fig 1.
Interaction of the human immune system with alien microorganisms.
In one scenario, the human immune system will interact with modified Earth microbes that have grown and adapted to an alien environment. In a second scenario, the human host defenses will encounter completely alien microbes, which may have different metabolic and cellular structures. It is a matter of speculation whether immune cells will be able to recognize such structures or, in contrast, to overreact to such an immune challenge.
Fig 2.
Interactions between modified Earth microorganisms and altered human immunity.
Different space environmental factors that could impact on the one hand the microorganisms and on the other the immune system of the astronauts, leading to different outcomes of these host–pathogen interactions. AAMP, alien associated molecular patterns.