Black Death Immunity has Negative Effects On Our Health Today, Study Finds
Black death immunity has negative effects on our health. It is possible that a genetic mutation that helped medieval Europeans escape the Black Death may also have a role, albeit a modest one, in an inflammatory condition that affects individuals today.
Scientists analyzed DNA from centuries-old bones to learn how the Black Death's bubonic plague shaped Europe's immune system. On October 19th, researchers reported in Nature that a version of a gene called ERAP2 was protective against this terrible wave of illness, leading to its increased prevalence. Scientists already knew that carrying that mutation increased the risk of Crohn's disease, a condition in which abnormal inflammationdamages the digestive tract.
The results show how these studies on ancient DNA can help actually understand diseases even now. And the trade-off is also very clear.- Says Mihai Netea, an infectious diseases specialist at Radboud University Medical Center in Nijmegen, Netherlands
The seven-year research entailed collecting DNA from three sets of skeletons found in London and Denmark: plague victims, people who died before the Black Death, and those who died 10 to 100 years after the pandemic.
London was one of the most affected areas during the 1348–1349 plague epidemic, and many of the samples were from Londoners who were interred in the East Smithfield plague pits. Human bones from five different burial sites throughout Denmark provided another 198 samples.
Researchers tested for the presence of the plague-causing bacteria Yersinia pestis by extracting DNA from dentine in the roots of patients' teeth. They looked for indications of genetic adaptation to the illness next.
It’s a LONG process, but in the end you have the sequence of those genes for those people from before, during and after the plague and you can ask: Do the genes one population carried looked different than the ones another population carried.- Professor of anthropology at McMaster University in Hamilton, Ontario, and coauthor Hendrik Poinar said in an email
Researchers isolated a form of the ERAP 2 gene that showed a striking correlation with the disease. In the London study, 40% of people who lived before the Black Death had the version of ERAP2 that protects against the plague. The mortality rate was halved after the Black Death. In Denmark, the difference in the percentages of samples buried before and after the plague was much more pronounced, shifting from roughly 45% to 70%.
Researchers have yet to determine the precise mechanism by which the ERAP 2 mutation protects individuals. Still, cultured cell investigations have shown that in those with this variant, an immune cell called a macrophage responds quite differently to Yersinia pestis, as detailed by Barreiro. In laboratory trials, macrophages from people who had the variation were more effective at eliminating germs than macrophages from those who did not have the variant.
The frequency of plague cases in modern communities is very low, so it is unknown whether or not the vaccine is still effective. Even though it hasn't been studied, likely, the change is also helpful against other infections.
The researchers found substantial evidence of genetic alterations at four chromosomal loci inside those areas, and they believe those changes were caused by the Black Death. A variation of ERAP2 was shown to be more common in subsequent studies. Hence, this development stood out.
When a host is infected with Y, immune cells from people who had this variant of ERAP2 were more effective at eliminating the plague bacterium than immune cells from people who did not have this variant. The same variation has been associated with Crohn's disease in studies of contemporary populations.
Experts in the area have suspected for some time that the same evolutionary adaptations that made our ancestors more resistant to infectious illnesses also led to harmful levels of immune activation in modern humans. This hypothesis is supported by the results of previous research on the epidemic.
The ERAP2 variation is an example of a protective mutation against the plague that has been found in genetic studies of modern Europeans looking for signs of past illness and in DNA studies of the bones of German plague victims from the 1600s.
This finding supports the idea that the genetic changes that have in the past made the human immune system stronger and better able to fight off ancient pathogens may have had unintended effects.