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Recent research suggests that the immune systems of mammals, including humans, may have difficulty detecting and responding to germs from other planets.
Microorganisms (such as bacteria and viruses) could exist beyond Earth, and there are plans to look for signs of them on Mars and some of Saturn and Jupiter’s moons.
Such organisms could be based on different amino acids (key building blocks of all life) than life forms on Earth.
Scientists at the universities of Aberdeen and Exeter tested how mammalian immune cells responded to peptides (combinations of amino acids) that contain two amino acids that are rare on Earth but commonly found in meteorites.
The immune response to these “extraterrestrial” peptides was “less efficient” than the reaction to the common ones on Earth.
The study, conducted in mice, whose immune cells function similarly to humans, suggests that extraterrestrial microorganisms could pose a threat to space missions, and on Earth if they were returned.
“The world is now too aware of the immune challenge posed by the emergence of new pathogens,” said Professor Neil Gow, deputy vice chancellor (Research and Impact) at the University of Exeter.
“As a thought experiment, we wonder what would happen if we were exposed to a microorganism that had been recovered from another planet or moon where life had evolved.
“There are some very unusual organic building blocks outside of planet Earth, and these could be used to form the cells of such alien microbes.
“Would our immune system be able to detect proteins made from these non-terrestrial building blocks if such organisms were discovered and brought back to Earth and then accidentally escaped?
“Our article addresses this hypothetical event.”
The study was led by scientists at the MRC Center for Medical Mycology, who moved from Aberdeen to Exeter last year.
The researchers examined the reaction of T cells, which are key to immune responses, to peptides containing amino acids commonly found in meteorites: isovaline and α-aminoisobutyric acid.
The response was less efficient, with activation levels of 15% and 61%, compared to 82% and 91% when exposed to peptides made entirely of amino acids that are common on Earth.
“Life on Earth depends on 22 essential amino acids,” said lead author Dr. Katja Schaefer of the University of Exeter.
“We hypothesized that life forms that evolved in an environment of different amino acids could contain them in their structure.”
“We chemically synthesize ‘exopeptides’ that contain amino acids that are rare on Earth, and we tested whether a mammalian immune system could detect them.
“Our research showed that these exopeptides were still being processed and T cells were still activated, but these responses were less efficient than those of ‘ordinary’ Earth peptides.
“Therefore, we speculate that contact with extraterrestrial microorganisms could pose an immunological risk to space missions aimed at recovering organisms from exoplanets and moons.”
The discovery of liquid water in various places in the solar system increases the possibility that microbial life may have evolved outside of Earth and could therefore accidentally enter the Earth’s ecosystem.
Which came first? Experiment in primordial protein reconstruction solves long-standing puzzle
Katja Schaefer et al., A weakened immune response to synthetic exopeptides predicts a potential biosecurity risk in exo-microorganism recovery, Microorganisms (2020). DOI: 10.3390 / microorganisms8071066
Provided by the University of Exeter
Citation: Mammalian Cells Might Fight to Combat Space Germs (2020, July 23) Retrieved July 23, 2020 from https://phys.org/news/2020-07-mammal-cells-struggle-space-germs .html
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