Research reveals that the human immune system comes from Asgard
All living organisms on Earth are divided into three groups: simple bacteria that do not have a nucleus to protect their genes inside the cells, complex eukaryotes that have a nucleus, and complex archaea that do not have a nucleus. Research results have been published that suggest that the immune mechanism that eukaryotes, including humans, have to fight viruses originates from the
Asgard archaea defense systems and their roles in the origin of eukaryotic immunity | Nature Communications
https://www.nature.com/articles/s41467-024-50195-2
Defense system common to all life came from 'Asgard' | Live Science
https://www.livescience.com/planet-earth/evolution/defense-system-common-to-all-life-came-from-asgard
Scientists first described a newly discovered group of archaea that bridges the gap between bacteria and eukaryotes in 2015. Named Asgard Archaea after the world of Norse gods, after its discovery in Loki's Castle, a hydrothermal vent on the ocean floor in the Arctic, the archaea have been positioned to revolutionize our understanding of the evolution of complex life.
Subsequent research suggested that the Asgard archaea that lived on Earth about 2 billion years ago were the ancestors of eukaryotes.
by Center for Geobiology/U. of Bergen
To gain a deeper understanding of how complex life evolved, Brett Baker and his team at the University of Texas at Austin focused on genes related to proteins that fight viruses.
After analyzing thousands of genomes and identifying tens of thousands of viral defense systems, the team decided to focus on genes that code for two proteins,
Argonaute is a protein named after the shape of a mutant found in the plant Arabidopsis, which resembles an octopus called Argonauta argo. It works by cutting up the genes of viruses, thereby preventing them from multiplying.
Meanwhile, viperin is the first innate immune system protein reported in humans, and plays a role in fighting off various viruses, including hepatitis C virus and human immunodeficiency virus (HIV).
As mentioned above, Argonaute and Viperin were found throughout the organisms analyzed, but the genetic similarity between Archaea and Eukaryotes was much higher than between Bacteria and the other two domains.
In particular, the team points out that the catalytic site, a part of the protein that is important for its function, has remained almost unchanged since eukaryotes diverged from the Asgard archaea about 2 billion years ago.
Baker says the fact that the catalytic site has remained largely unchanged over the years speaks to how well the system works.
'Our findings support the idea that Asgard archaea played an important role in the origin of eukaryotic antiviral defense systems,' the team wrote in their paper.
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