French researchers have recently identified a protein in humans, whose role remained a mystery until today. Baptized SIRAL, this protein area would be at the heart of a principle of biological conservation opening the way to progress in immunotherapy, a type of medical treatment stimulating the immune system of patients.
A field of expanding research
As a reminder, innate immunity is the first line of non -specific defense of the organization Against pathogens and other threats. This brings together physical barriers (skin, mucous membranes), chemical barriers (mucus, tears) but also, cells such as phagocytes and other lymphocytes. For a long time, science thought it had identified most of these defenses but that was without counting The notion of ancestral immunity.
This is an increasingly explored field of research, as indicated by a publication of the National Institute of Health and Medical Research (Inserm) on July 24, 2025, relating a study published in the journal Science on the same day. The objective? Understand the evolutionary links between bacterial and human proteins and more precisely, identify proteins involved in innate immunity in humans while the latter
derive from those present in bacteria.
A protein area with a very important role
At the Institut Curie, a team from the Immunity and Cancer Unit (U932) has reconstructed the evolutionary history of genes by phylogeny (or phylogenesis). Researchers have highlighted in humans the presence of the SIRAL protein domaina counterpart in the SIR2 domain in bacteria. Note that Sir2 plays an important role against phages, viruses infecting bacteria. After the entry of a phage, the protein domain triggers the degradation of an essential molecule to cellular metabolism and causes the death of the infected cell. The objective of this action is Protect the rest of the healthy cells.
The fact is that scientists have demonstrated the role of Siral in innate immunity in humans, as well as its ability to degrade an essential molecule for cellular metabolism and energy production: nicotinamide adenine dinucleotide (NAD). This discovery is all the more interesting since it concerns not a single protein but a whole family usually present in 19 % of eukaryotic genomes analyzed and distributed in five large lines.
Credits: Inserm
Future treatments taking into account bacterial evolution
In addition, specialists have shown that Siral was acting like a central regulator of the Toll-Like Receptors receptor route (TLR). TLRs are receptors capable of detecting typical signals from pathogens. Thus, the Siral could Facilitate the expression of pro-inflammatory genesthen the trigger for the immune reaction. Conversely, the non -presence of the SIral is synonymous with a strong alteration of the inflammatory response, whether it is a question of a viral or bacterial infection.
“With Siral, we show that elements inherited from bacteria can play a central role in eukaryotic immune mechanisms, especially human. But more broadly, ancestral immunity gives us access to an unsuspected reservoir of immune mechanisms. »»said Enzo Poirier, team leader in the U932 unit.
For researchers, their discovery is proof that if immune mechanisms of bacterial origin are actually present in organisms, they are subject to a
Large conservation within the living. In addition, there is potentially a question of involvement in all eukaryotic organizations, including humans. The study authors believe that their work can open the way for the development of immunotherapy treatment taking into account bacterial evolution.
