Prof. Yehu Moran from the Hebrew University, one of the leaders of the research: "Sea lilies have been alive and thriving for the past 600 million years despite the presence of many viruses, so their immune system is probably effective. A possible disadvantage that I can suggest is that complex systems have a significant metabolic (energetic) cost." And also: what can be learned from this about the human immune system?
Viruses are absolute parasites. They live inside us, their hosts, and multiply inside our cells, as they waste our resources and may even kill us. In fact, they cannot reproduce outside our bodies or outside the bodies of any animals, from sea urchins to humans. This is how an evolutionary arms race takes place, between the viruses and their hosts, and in which antiviral immune systems change at high speed. As a result, the immune system of vertebrates such as fish, mice and humans is very different from that of worms and insects for example. in the laboratory of Prof. Yehu Moran from the Department of Ecology, Evolution and Behavior at the Hebrew University, the researchers examined the difference between the antiviral immune system of vertebrates, and that of The starry sea lily nematostella vectensis, An animal belonging to an ancient group, whose evolutionary split from vertebrates is much earlier than that of worms and insects. This rose is a species of weed that can be grown in the lab and researchers can genetically engineer it.
In the last decade and a half, the sequencing of the genomes of animals representing ancient groups of animals such as the stingrays (sea anemones, jellyfish, corals, etc.) has revealed a surprising finding - even though the time of the group's split from the vertebrates is earlier than that of the insects, their genomes sometimes show points of unmistakable similarity expected for genomes of vertebrates that are not shared by insects and worms.
Prof. Moran and the people of his laboratory focused on the systems that exist inside the rosette cells and allow the individual cell to notice that it has been infected with a virus and to respond to the infection. These systems have been designed during evolution to recognize characteristics of a virus that are not present in a healthy cell of the host. Because these systems work differently and use different components in vertebrates versus invertebrates, it was assumed that in simple animals like sea anemones the system would work like in worms or flies. Unexpectedly, he showed up A new study published in the scientific journal Molecular Biology and Evolution of the Society for Molecular Biology and Evolution, led by Prof. Moran's research group, Because the antiviral system in sea anemones is extremely complex and includes components that exist in worms, but also components that until now were considered unique to vertebrates, when it was widely assumed that they appeared only at a late stage of evolution.
The "modern" components include many proteins that participate in the cellular response to interferon, a molecule unique to vertebrates. The interferon is secreted from the cell attacked by the virus and signals the immune system about the damage. As a result, specialized cells of the immune system are sent to the damaged cell to attack the virus. Although the sea anemone does not have interferon, a central part of its antiviral response is reminiscent of the response of vertebrates to this molecule, the corresponding mechanism in the sea anemone, and the researchers believe that in the near future they may discover a protein in the anemone that corresponds to interferon in terms of activity, and probably preceded it in evolution.
The researchers used advanced genetic sequencing methods to identify which genes respond to the viral markers, and biochemical methods to identify receptors used by the rosette cells in recognizing and binding these markers. Also, they used genetic methods in order to prevent the activity of the receptors, which resulted in the cessation of the antiviral response and proved the involvement of the receptors in the recognition. The results of the study indicated that ancient animals that lived 600 million years ago, and from which the invertebrates such as sea anemones, flies and worms as well as vertebrates such as the fish and mammals evolved, used a complex immune system. In addition, The conclusion from the study is that each of the animal groups, with the exception of the anteaters, lost different components of this complex system during evolution. This is an example of how the level of complexity and sophistication of a biological system does not always increase throughout evolution, and sometimes a loss of components occurs due to the specialization of the system in other defense strategies that use other components.
High energy price
What are the shortcomings found regarding this ancient immune system? "Sea lilies have lived and thrived in the sea for the last 600 million years despite the presence of many viruses, so their immune system is probably effective. A possible downside I can suggest is that complex systems have a significant metabolic (energetic) cost. That is, maintenance of a complex system with many components requires a significant investment of energy from the animal. Conversely, when a system is 'specialized' and has fewer components, it is 'cheaper' to maintain. That is, it requires an investment of less energy," explains Prof. Moran.
In addition to the published research, Prof. Moran's group also intends to begin investigating the composition of the antiviral system of corals - distant cousins of the sea lily, which are of tremendous ecological importance, and which in recent years suffer from deadly diseases whose origin is often unclear and may be viruses that have not yet been identified .
Can the research say anything about the human immune system? Prof. Moran emphasizes that the human immune system has lost certain components that were present in our common ancestor and the sea lily. On the other hand, humans have had the expansion and specialization of certain parts of the system such as the interferon in the immune system (humans are mammals and mammals are part of the vertebrates). "I believe that further research will be able to deal with the question of this connection, and teach us more about the development of the immune system in animals from prehistory to the present day," concluded the researcher.
More of the topic in Hayadan:
