Findings from two recently published studies in the Journal Cell, demonstrated that individuals with African ancestry are more likely to have a stronger immune response to infection than those of European ancestry.
The Canadian-US research team led by Luis Barreriro, assistant professor at the University of Montreal’s Department on Pediatrics and researcher at the Sanite-Justine University Hospital Center, conducted their study by drawing white blood cells from 175 Americans, 80 from African decent and the remainder were European descent.
In a controlled laboratory environment, the researchers infected the white blood cells with listeria and salmonella bacteria so they could monitor the response. Nearly 24 hours after the infection, the white blood cells of African-Americans killed the bacteria three times faster than in European Americans.
The second study examined genetic differences in RNA sequencing between African-American and European genomes. The French research team, led by Lluis Quintana-Murci at the Pasteur Institute in France, had findings similar to the Canadian-US team. However, in addition to differences in inflammatory response between African Americans and European Americans, there was also an evolutionary component, signaled by natural selection that affected the immune system response.
It turns out that introducing Neanderthal variations into the Europeans genomes, decreased the pro-inflammatory immune responses to bacterial and viral infections for Europeans. Both teams suggested that the genetic divergence could be explained by the Neanderthals who colonized Europe, but not Africa before their extinction about 40,000 years ago. Researchers also speculated that there may some other evolutionary factors that contribute to the genetic variations between African American and European American ancestry.
Senior researcher Luis Barreiro commented that, “The strength of the immune response was directly related to the percentage of genes derived from African ancestors. "Basically, the more African you have in your genome, the stronger you're going to respond to infection," Barreiro said.
Scientists believe that these findings might lead to treatments that may reduce chronic health risks for African-Americans. However, there also seems to be a downside.
While it’s true that a strong immune response triggers the inflammatory response, which attacks and defeats infection, too much inflammation can also cause greater susceptibility to other diseases. Too much inflammation can lead to high blood pressure, damage to organs such as heart and liver, and increase the susceptibility for autoimmune diseases such as Lupus and Crohn’s disease.
Barreiro and his colleagues concluded that, “The genes and pathways we’ve identified constitute good candidates to explain differences we are seeing in disease between the two population groups,”. Barreriro further said, “Now that we have these genetic variants, we can test if these variants are associated with differences in susceptibility to diseases”.
These results may also help to further explain some biological differences that contribute to health disparities. Overall, there is these studies only represent a beginning point for exploring why individuals of different ancestry react differently to the presence of viruses and bacteria.
Future studies will also examine the influence of other factors such as environment and behavior on differences in immune response. Both studies were published online in the October 20th issue of the journal Cell.