Neanderthal genes gave humans immunity boost, allergies: study

Interbreeding of Neanderthals with modern humans in Europe thousands of years ago may have left us with gene variations that increased our ability to ward off infection, new research suggests.
However, this inheritance from Neanderthals may have also left some people more prone to allergies, researchers said.
The findings reported in two studies add to evidence for an important role for interspecies relations in human evolution and specifically in the evolution of the innate immune system, which serves as the body's first line of defence against infections.
The researchers focused on a list of 1,500 genes known to play a role in the innate immune system.

They then examined patterns of genetic variation and evolutionary change in those regions relative to the rest of the genome at an unprecedented level of detail.
Finally, they estimated the timing of the changes in innate immunity and the extent to which variation in those genes had been passed down from Neanderthals.

"We found that interbreeding with archaic humans - the Neanderthals and Denisovans - has influenced the genetic diversity in present-day genomes at three innate immunity genes belonging to the human Toll-like-receptor family," said Janet Kelso of the Max Planck Institute for Evolutionary Anthropology in Germany.
"These, and other, innate immunity genes present higher levels of Neanderthal ancestry than the remainder of the coding genome," said Lluis Quintana-Murci of the Institute Pasteur and the CNRS in France.

Earlier studies have shown that one to six per cent of modern Eurasian genomes were inherited from ancient hominins, such as Neanderthal or Denisovans.
Both the studies highlight the functional importance of this inheritance on Toll-like receptor (TLR) genes - TLR1, TLR6, and TLR10.
These TLR genes are expressed on the cell surface, where they detect and respond to components of bacteria, fungi, and parasites.
These immune receptors are essential for eliciting inflammatory and anti-microbial responses and for activating an adaptive immune response.
"What has emerged from our study as well as from other work on introgression is that interbreeding with archaic humans does indeed have functional implications for modern humans, and that the most obvious consequences have been in shaping our adaptation to our environment - improving how we resist pathogens and metabolise novel foods," said Kelso.

The research was published in the American Journal of Human Genetics.