Racial immunology
The immune system of African Americans reacts more strongly to infections
Professor of the Faculty of Pediatrics at the University of Montreal (Canada) Luis Barreiro and his colleagues have found that Americans of African descent have stronger immunity against bacterial infections compared to their white fellow citizens. As it turned out, the causes of this phenomenon are mostly genetic in nature. The results of the study are published in the journal Cell (Nédélec et al., Genetic Ancestry and Natural Selection Drive Population Differences in Immune Responses to Pathogens), they are summarized in a press release of the University Immune system of African Americans responds more strongly to bacterial infection.
175 Americans took part in the study, half of whom were from Africa, and the other half were of European origin. Scientists isolated macrophages (agents of the immune system) from their blood samples and set them against bacteria of the genus listeria and salmonella. Over the next day, macrophages from the blood of African Americans killed pathogenic microbes three times faster. The research team also established the genetic causes of this phenomenon.
However, the authors of the study warn against a straightforward interpretation of their conclusions. The "strength" of the immune system in this case does not mean that it is better. For example, people with a highly sensitive immune response are more likely to suffer from autoimmune diseases. Perhaps this is why Americans of African descent are more susceptible to tuberculosis and scleroderma.
"Although we found these differences in immune responses between African and European Americans, we are still unable to demonstrate that evolution led to the observed differences. One of our hypotheses is that in the prehistoric period, after human populations migrated from Africa, they were exposed to fewer pathogenic microorganisms (bacteria, viruses, parasites), which led to a decrease in the immune response and, thus, reduced the phenomena of tissue inflammation. This decrease in the immune response (and, consequently, inflammation) is most likely an advantage due to the adverse effects of acute or chronic inflammation, which become the main factors contributing to the development of autoimmune inflammatory diseases," says Dr. Barreiro.
Another hypothesis is that the weaker immune response found in Europeans is a consequence of less vigorous natural selection in an environment in which there was a less diverse, or at least a different pathogenic environment, compared to Africa.
Neanderthal genes, which are present in all people who have developed outside Africa, also play a role in the immune response to infection. The analysis showed that about 3% of the genes involved in differences in immune responses in European Americans are of Neanderthal origin.
"We still have a lot to do. For example, we have not yet studied the immune response to the presence of viruses and parasites. In addition, genetics explains only about 30% of the observed differences in immune responses. Our future research should focus on other factors, including the influence of the environment and our behavior. The idea is to find immune mechanisms that can explain why people react differently to infection with certain viruses and bacteria," says Luis Barreiro.
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25.10.2016