A genetic variant that boosts Crohn's disease risk may have helped people survive bubonic plague :
Researchers used DNA collected from centuries-old remains to discern the fingerprints that bubonic plague during the Black Death left on Europeans' immune systems. This devastating wave of disease tended to spare those who possessed a variant of a gene known as ERAP2, causing it to become more common, researchers report October 19 in Nature. That variant is already known to scientists for slightly increasing the odds of developing Crohn's disease, in which errant inflammation harms the digestive system.
The results show "how these studies on ancient DNA can help actually understand diseases even now," says Mihai Netea, an infectious diseases specialist at Radboud University Medical Center in Nijmegen, Netherlands, who was not involved with the study. "And the trade-off is also very clear."
Caused by the bacterium Yersinia pestis, bubonic plague once killed 60 percent of those infected. [...]
By sparing individuals whose immune systems bear certain traits, pathogens such as Y. pestis have shaped the evolution of the human immune system. Studies are teasing out the ways the massive winnowing of the plague altered Europeans' immune-related genetics.
[...] For some time now, researchers in the field have theorized that adaptations that helped our ancestors fortify their immune systems against infectious diseases can contribute to excessive, damaging immune activity. Earlier studies of plague offer support for this idea. A genetic analysis seeking traces of historical disease in modern Europeans and a study of DNA from the remains of 16th century German plague victims both turned up what appear to be protective changes against the plague that, like the ERAP2 variant, are linked with inflammatory and autoimmune conditions.
Likewise, this latest discovery suggests that genetic changes that have amped up the human immune response in the past, empowering it to better fight off ancient infections, can come at a cost. "If you turn the heat too much, that leads to disease," Barreiro says.
Journal Reference:
Klunk, J., Vilgalys, T.P., Demeure, C.E. et al. Evolution of immune genes is associated with the Black Death. Nature (2022). 10.1038/s41586-022-05349-x
