Mammal cells could struggle to fight space germs

July 23, 2020

The immune systems of mammals - including humans - might struggle to detect and respond to germs from other planets, new research suggests.

Microorganisms (such as bacteria and viruses) could exist beyond Earth, and there are plans to search for signs of them on Mars and some of Saturn and Jupiter's moons.

Such organisms might be based on different amino acids (key building blocks of all life) than lifeforms on Earth.

Scientists from the universities of Aberdeen and Exeter tested how mammal immune cells responded to peptides (combinations of amino acids) containing two amino acids that are rare on Earth but are commonly found on meteorites.

The immune response to these "alien" peptides was "less efficient" than the reaction to those common on Earth.

The study - conducted in mice, whose immune cells function in a similar way to those of humans - suggests extra-terrestrial microorganisms could pose a threat to space missions, and on Earth if they were brought back.

"The world is now only too aware of the immune challenge posed by the emergence of brand new pathogens," said Professor Neil Gow, Deputy Vice-Chancellor (Research and Impact) 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.

"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.

"Would our immune system be able to detect proteins made from these non-terrestrial building blocks if such organisms were discovered and were brought back to Earth and then accidently escaped?

"Our paper addresses this hypothetical event."

The study was led by scientists at the MRC Centre for Medical Mycology, which moved from Aberdeen to Exeter last year.

Researchers examined the reaction of T cells, which are key to immune responses, to peptides containing amino acids commonly found on 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 relies on essential 22 amino acids," said lead author Dr Katja Schaefer, of the University of Exeter.

"We hypothesised that lifeforms that evolved in an environment of different amino acids might contain them in their structure.

"We chemically synthetised 'exo-peptides' containing amino acids that are rare on Earth, and tested whether a mammal immune system could detect them.

"Our investigation showed that these exo-peptides were still processed, and T cells were still activated, but these responses were less efficient than for 'ordinary' Earth peptides.

"We therefore speculate that contact with extra-terrestrial microorganisms might pose an immunological risk for space missions aiming to retrieve organisms from exoplanets and moons."

The discovery of liquid water at several locations in the solar system raises the possibility that microbial life may have evolved outside Earth, and could therefore be accidently introduced into the Earth's ecosystem.
-end-
The study was funded by the Medical Research Council (MRC) and Wellcome.

The paper, published in the journal Microorganisms, is entitled: "A weakened immune response to synthetic exo-peptides predicts a potential biosecurity risk in the retrieval of exo-microorganisms."

University of Exeter

Related Immune System Articles from Brightsurf:

How the immune system remembers viruses
For a person to acquire immunity to a disease, T cells must develop into memory cells after contact with the pathogen.

How does the immune system develop in the first days of life?
Researchers highlight the anti-inflammatory response taking place after birth and designed to shield the newborn from infection.

Memory training for the immune system
The immune system will memorize the pathogen after an infection and can therefore react promptly after reinfection with the same pathogen.

Immune system may have another job -- combatting depression
An inflammatory autoimmune response within the central nervous system similar to one linked to neurodegenerative diseases such as multiple sclerosis (MS) has also been found in the spinal fluid of healthy people, according to a new Yale-led study comparing immune system cells in the spinal fluid of MS patients and healthy subjects.

COVID-19: Immune system derails
Contrary to what has been generally assumed so far, a severe course of COVID-19 does not solely result in a strong immune reaction - rather, the immune response is caught in a continuous loop of activation and inhibition.

Immune cell steroids help tumours suppress the immune system, offering new drug targets
Tumours found to evade the immune system by telling immune cells to produce immunosuppressive steroids.

Immune system -- Knocked off balance
Instead of protecting us, the immune system can sometimes go awry, as in the case of autoimmune diseases and allergies.

Too much salt weakens the immune system
A high-salt diet is not only bad for one's blood pressure, but also for the immune system.

Parkinson's and the immune system
Mutations in the Parkin gene are a common cause of hereditary forms of Parkinson's disease.

How an immune system regulator shifts the balance of immune cells
Researchers have provided new insight on the role of cyclic AMP (cAMP) in regulating the immune response.

Read More: Immune System News and Immune System Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.