A recent study indicates that the immune systems of humans and other complex life forms may have evolved from an ancient group of microorganisms known as Asgard Archaea. These microbes, believed to have existed around 2 billion years ago, have offered new insights into the origins of crucial proteins that help organisms combat viral infections. The research, led by microbiologists Pedro Lopez-León from Radboud University and Brett Baker, an associate professor at the University of Texas at Austin, provides a deeper understanding of how our immune system came to be.
The Significance of Asgard Archaea
The evolution of life is typically divided into three main domains: Bacteria, Eukaryotes, and Archaea.. Bacteria consist of simple cells that lack a nucleus, while eukaryotes are more complex organisms that contain their DNA within a nucleus and have specialized organelles.
although they do not have a nucleus, share energy-processing characteristics similar to those of eukaryotes.
Within the Archaea domain, the Asgard superfamily, discovered in 2015, is crucial for bridging the evolutionary divide between bacteria and eukaryotes. These archaea received their name from Norse mythology, as they were found near a hydrothermal vent in the Arctic known as “Loki’s Castle.”
Immune Proteins with Ancient Roots
The researchers analyzed thousands of genomes across a diverse range of life forms, identifying tens of thousands of viral defense mechanisms. Their research focused on two proteins common to all three domains of life: viperin and argonaute. Viperin is an integral part of the human innate immune system, helping to combat viruses by inhibiting their replication within infected cells. Argonaute, initially discovered in plants, also prevents viral replication by degrading their genetic material.
The genes for these proteins show striking similarities between archaea and eukaryotes, suggesting they originated from a shared ancestor within the Asgard lineage, as detailed in findings published in Nature Communications. Furthermore, crucial catalytic sites in these proteins have remained relatively unchanged for over two billion years, hinting at their effectiveness in defending against viral threats.
