Alien germs in outer space may pose threat to human immune system, create risk for future missions: Study
The discovery of ocean worlds within our solar systems has brought some cheer for alien life hunters. Even if these space bodies are home to tiny germs, a chance encounter with them might present challenges to mammals, including humans.
Giving rise to the theory is a new study that looked at how the immune cells of mice responded to alien germs. "Although studies on mice are often comparable to what would happen in humans, we can only speculate that human cells would behave in the same way," lead author Dr Katja Schaefer, of the University of Exeter, told MEA WorldWide (MEAWW).
The study comes at a time before NASA's Mars 2020 mission to look for signs of past life on the Red Planet takes off. Experts are hoping to bring back rock samples too. In 2025, the space agency is aiming to send the first women and the next man to the moon. Further, the presence of liquid water in the moons of Saturn and Jupiter have also raised the possibility of finding microbes. NASA has also updated its policies for robotic and space missions to safeguard other planetary bodies, including our Earth, from possible contamination.
"The world is now only too aware of the immune challenge posed by the emergence of brand new pathogens," said Dr Neil Gow, Deputy Vice-Chancellor at the University of Exeter. "As a thought experiment, we wondered what would happen if we were to be exposed to a microorganism that had been retrieved from another planet or moon where life had evolved," he added.
On Earth, life depends on 22 essential amino acids, which make up proteins. The researchers believe that space germs could have different ones. So they artificially produced two extra-terrestrial peptides -- a combination of amino acids. These alien peptides hitched a ride on meteorites that crashed into our planet. "Some very unusual organic building blocks exist outside of the planet Earth, and these could be used to make up the cells of such alien microbes," Gow added.
The team designed experiments to test how a specific immune cell called T cells responds to the extra-terrestrial peptides. These cells play a crucial role in protective immunity by recognizing peptides from pathogens and clearing them from the body, Dr Schaefer explained.
When exposed to extra-terrestrial peptides -- isovaline and α-aminoisobutyric acid -- the T cells failed to activate to its full potential, the researchers observed. Their activation levels ranged between 15% and 61%, which pales in comparison to 82%, and 91% achieved when exposed to Earth's natural peptides. Dr Schaefer speculates that contact with extra-terrestrial microorganisms might pose an "immunological risk for space missions that retrieve organisms from exoplanets and moons."
For T cells to get efficiently activated, they need to be able to recognize a foreign peptide. They also should successfully process the alien agent. "Reduced T cell activity could result from altered activity during any of the steps that lead to T cell activation," explained Dr Schaefer. Further studies can investigate the reasons behind the reduced T cell repsonse, she added.
The researches have looked at one part of the immune system's response. "Additional future studies could go a step further to answer the question if the mammalian immune system would produce antibodies against exo-peptides," she questioned.
The study is published in Microorganisms.