People who survived the bubonic plague in parts of Europe had mutations in their genes that likely offered protection against the disease, but those same mutations passed down to survivors' descendants may increase the risk of autoimmune disease, research published Oct. 19 in Nature suggests.
To conduct the study, researchers extracted DNA from people in London and Denmark who died from the plague 700 years ago. They compared what they found to DNA from people who died before the plague, also known as the Black Death, and after it.
They found several mutations that likely gave survivors protection from Yersinia pestis, the bacterium that causes the plague. One gene that stood out was a variant of ERAP2, which appeared to give people a 40 percent survival advantage from the plague.
That same gene is linked to an increased risk of certain autoimmune diseases today, such as Crohn's disease and rheumatoid arthritis. That is because the gene likely enhances an inflammatory process that clears out infection, but an overactive immune system can also lead to autoimmune diseases, researchers told NPR.