Europeans who survived the plague left their descendants with a genotype with a tendency to arthritis

Scientists have identified the genetic traits of those who survived the Black Death more than 700 years ago, but which today are associated with increased susceptibility to certain autoimmune diseases.

A study of centuries of DNA from victims and survivors of the 14th-century bubonic plague found that people with what scientists call a “good” variant of a particular gene, known as ERAP2, survived much more frequently.

The results, published in the journal Nature, shed light on how the Black Death, which wiped out about 50% of Europe’s population, affected the evolution of immune genes like ERAP2, setting the course for how people today respond to disease.

The researchers noted that a “selective” ERAP2 variant is also a known risk factor for Crohn’s disease and has been linked to other autoimmune diseases such as arthritis.

Luis Barreiro, professor of genetic medicine at the University of Chicago Medical Center in the US and co-author of the study, said: “To my knowledge, this is the first demonstration that the Black Death was indeed an important selective pressure.”

More than 500 ancient DNA samples have been extracted for the study from human remains, including those buried in London’s East Smithfield plague pits, which were used for mass graves in 1348 and 1349.

They then looked for signs of any genetic adaptation associated with the plague caused by the bacterium Yersinia pestis. It has been found that having two copies of the “good” ERAP2 gene allows people to produce functional proteins – molecules that help the immune system recognize infection.

According to scientists from McMaster University, the University of Chicago, the Pasteur Institute and others, these copies of ERAP2 allowed “immune cells to neutralize Y pestis more effectively.”

Having the variant would have made a person about 40% more likely to survive the Black Death, compared to those who didn’t have it.

genomes, but go unnoticed in modern populations.

“These genes balance selection — what provided amazing protection during hundreds of years of plague epidemics now brings autoimmune diseases to the owners of these genes,” he added.

“An overactive immune system may have been great in the past, but today in the environment it may not be as helpful,” the scientist noted.