The Black Death Still Affects the Human Immune System | CNN

Sign up for CNN’s Wonder Theory science newsletter. Explore space with news about fascinating discoveries, scientific advances, and more. CNN — The world’s deadliest epidemic, the Black Death, killed half of the population of medieval Europe in seven years in the 14th century and changed the course of human history. But what about the survivors of the event that remains the largest fatality ever recorded? Who lives and who dies is more important than luck, according to a new study published Wednesday in the journal Nature. According to a study published in the journal Nature, analysis of the centuries-old DNA of plague victims and survivors identified key genetic differences that helped people survive the plague. These genetic differences still shape the human immune system today, and genes that once provided protection against infectious diseases are now linked to greater susceptibility to autoimmune diseases such as Crohn’s disease and rheumatoid arthritis, the study found. “We are descendants of people who have survived epidemics of the past … Understanding the evolutionary mechanisms that contributed to our survival is not only important from a scientific point of view, but can inform today about the mechanisms and genetic determinants of susceptibility to disease. .” Study co-author Luis Barreiro, professor of genetic medicine at the University of Chicago, said in an email. The seven-year study involved the extraction of DNA isolated from the remains of three different groups unearthed in London and Denmark. Plague victims, those who died before the Black Death, and those who died between 10 and 100 years after the outbreak of the plague. More than 300 samples came from London, a city particularly hard hit by the plague, including individuals buried in the East Smithfield plague pit used for mass burials when the outbreak peaked in 1348-1349. An additional 198 samples were taken from human remains buried in five locations in Denmark. By extracting DNA from dentin in the root of an individual’s teeth, the researchers were also able to confirm the presence of Yersinia pestis, the bacterium that causes the plague. Then they searched for signs of genetic adaptation to the disease. “It’s a long process, but eventually you have the genetic sequence of those people before, during, and after an epidemic, and you can ask yourself: Do the genes in one group look different from the genes in another?” Co-author Hendrik Poinar, professor of anthropology at McMaster University in Hamilton, Ontario, said in an email. The team identified a mutation in a specific gene known as ERAP 2 that appears to be strongly associated with infectious diseases. ERAP2 variants that had been shown to protect against the plague before the Black Death were found in 40% of individuals included in the London study. After the Black Death, it was 50%. In Denmark, the percentile disparity was even more pronounced. Changed from about 45% of samples buried before the Black Death to 70% of samples buried after. The team doesn’t yet know exactly why this variant conferred a protective function, but laboratory experiments on cultured cells showed that in people with the ERAP 2 mutation, immune cells known as macrophages induced very different responses to Yersinia pestis, says Barreiro. explained. . Macrophages from individuals with the mutation were better able to kill bacteria in laboratory experiments than macrophages from individuals without the mutation. “Given the very small number of cases in the current population, I don’t know if the epidemic can still be prevented, but I guess it should be done,” he said. Although this strain is not part of the study, it may also be beneficial against other pathogens. A disadvantage of this variant is that it is associated with greater susceptibility to autoimmune diseases such as Crohn’s disease, in which the immune system becomes overactive. “This suggests that the population that survived the Black Death has paid a price,” Barreiro said. “It’s the immune system that increases our susceptibility to ourselves,” said Barreiro. He said the Covid-19 outbreak is unlikely to shape our immune systems in a similar way. The main reason is that the disease effectively kills people after reproductive age. This is because the genes that confer protection are less likely to be passed on to the next generation. David Enard, a professor of ecological and evolutionary biology at the University of Arizona who was not involved in the study, said changes in human genetic makeup that occur in decades are rare examples of rapid natural selection. In a commentary accompanying the study, he said: “The advantages of the study were that it analyzed a large number of samples and the narrow time period during which the samples were taken. “Evolutionary biologists have previously wondered about the possibility of natural selection during the Black Death, but many samples A proper investigation would not have been possible without accurate dating of

#Black #Death #Affects #Human #Immune #System #CNN

Leave a Comment

Your email address will not be published. Required fields are marked *