Half of the European population has been wiped out and society as a whole has been devastated.
The plague bacterium Yersinia pestis was present in Europe between 1347 and 1353 and is known as one of the greatest killers of all time.
And now scientists in the Nature magazine that the bacterium has also left an indelible mark on our genetic material, making diseases such as rheumatoid arthritis, diabetes and chronic intestinal inflammation more common today.
Study the cemeteries of the plague
In the new study, scientists analyzed up to 516 ancient DNA samples, taken from the bones and teeth of people who died before, during or shortly after the plague outbreaks in London and Denmark, respectively.
One of their theories was that the bubonic plague caused significant changes in the development of our immune system during its deadly journey through Europe, Asia and Africa. And they were right.
In the genes that regulate the immune system, the researchers found four genetic variations that either protected against Y. pestis or increased susceptibility to it. For example, changes have determined who survived the pandemic and who did not.
Genes strengthen the soldiers of the body
They found the most striking change around the ERAP2 gene, which ensures that the immune system can detect and fight infections.
This is done by the immune system’s “scavengers”, macrophages, who ingest and digest viruses and bacteria. The macrophages then cut the bacteria and carry them to the B and T cells of the immune system, so they can attack. It works a bit like an alarm system.
The new study shows that people with two identical copies of the ERAP2 gene were 40 percent more likely to survive the plague than those who didn’t.
Increased risk of serious illness
Survivors could then pass these changes on to their descendants, who then had an advantage in subsequent pandemics.
But while genetic variations in the Middle Ages served primarily as a defense against the common plague, today the same changes can increase the risk of autoimmune diseases such as rheumatoid arthritis, diabetes, and chronic intestinal inflammation, where the immune system attacks the body’s own tissues. body. The researchers write this in their report.
Research leader Hendrik Poinar of McMaster University in Hamilton, Canada compares the two copies of the ERAP2 gene with scissors that cut bacteria and viruses.
In the Middle Ages these scissors were crucial for the survival of the individual, while now paradoxically they can have a harmful side effect.
“The genes you got from your ancestors to survive the Black Death go back to a time when infectious diseases were a major threat. But now hyperactive scissors see your own tissue as an enemy and attack it,” he says. Mail online.
