In a new review, researchers found that some of the same genetic mutations allowing humans to fend off deadly infections also make us more prone to certain inflammatory and autoimmune diseases, such as Crohn’s disease.
They describe how ancestral origins impact the likelihood that people of African or Eurasian descent might develop immune-related diseases.
The authors also share evidence that the human immune system is still evolving depending on a person’s location or lifestyle.
The research was done by a team at Radboud Institute for Molecular Life Science in the Netherlands.
In the past, people’s lifespans were much shorter, so some of these inflammatory and autoimmune diseases that can appear in the second half of life were not so relevant.
Now that people live so much longer, it is possible to see the consequences of infections that happened to ancestors.
One of the body’s best defenses against infectious diseases is inflammation.
The team compiled data from genetics, immunology, microbiology, and virology studies and identified how the DNA from people within different communities commonly infected with bacterial or viral diseases was altered, subsequently allowing for inflammation.
The found while these changes made it more difficult for certain pathogens to infect these communities, they were also linked to the emergence—over time—of new inflammatory diseases such as Crohn’s disease, Lupus, and inflammatory bowel disease.
The team says there seems to be a balance. Humans evolve to build defenses against diseases, but they are not able to stop the disease from happening, so the benefit they obtain on one hand also makes them more sensitive to new diseases on the other hand.
The team also writes about how the early-human ancestors of Eurasians lived in regions still inhabited by Neanderthals and interbred.
Today, people with remainders of Neanderthal DNA can be more resistant against HIV-1 and ‘staph’ infections but are also more likely to develop allergies, asthma, and hay fever.
The team plans to see how human immune systems are evolving in real-time because of modern lifestyle changes.
African tribes that still engage in hunting have greater bacterial gut diversity than urbanized African-Americans that eat store-bought foods.
Also, changes in hygiene patterns seen in the last two centuries have improved sanitation, drinking water, and garbage collection, and have led to reduced exposure to infectious pathogens relative to previous times.
As humans move toward processed foods and stricter hygiene standards, their bodies adapt by developing what researchers call “diseases of civilization,” such as type 2 diabetes.
The lead author of the study is Jorge Dominguez-Andres, a postdoctoral researcher.
The study is published in the journal Trends in Immunology.
Copyright © 2019 Knowridge Science Report. All rights reserved.
