November 24, 2013
Modern Spy-Like Immune Gene May Have Come From Neanderthals
Ranjini Raghunath for redOrbit.com - Your Universe Online
A team of European researchers has recently discovered a protein molecule that helps the immune system identify threats and invaders. The molecule, a receptor belonging to the human leukocyte antigen (HLA) system, may have been inherited from Neanderthals, they report.
HLA receptors help the immune system identify threats by tagging cells as either friendly or foreign. When a protein looks suspicious, immune cells called macrophages break it down into pieces. HLA receptors then act as presenting “platforms,” holding out these pieces for patrolling immune cells called T-cells. Like an inspector checking for quality, T-cells scan these pieces of proteins to find out if they belong to the human body or to a foreign organism.
"This function can be compared to a text which is identified by a spy as being suspicious, based on just a few letters of a word,” said Professor Norbert Koch, University of Bonn immunologist and senior author of the paper, in a statement.
If there is no foreign protein, the receptors present proteins belonging to our own cells to the T-cells.
These receptors are assembled from just eight amino acids (the building blocks of proteins) in more than 1000 different combinations. More combinations mean a wider range of foreign proteins that the receptor can bind to and present to T-cells – a function that is crucial to identifying the millions of foreign organisms that enter our body.
So far, three receptors had been identified. Now, a fourth has jointly been discovered by the researchers from the University of Düsseldorf, the Technical University of Munich, Jacobs University Bremen, Cambridge University and the University of Bonn.
The collaborative team also identified the gene sequences that control how the receptor is assembled. These gene sequences are present in more than two-thirds of modern-day Europeans.
The researchers also found that these gene sequences were rare in sub-Saharan African populations. This pointed to the fact that these genes might have appeared much later in the evolutionary timescale, around the time Neanderthals colonized Europe.
"When early man, the ancestor of today's humans, left Africa and migrated a few hundred thousand years ago to Europe, he did not yet have this receptor,” Koch stated.
With this in mind, the researchers compared the receptor gene sequences to those present in the Neanderthal gene database put together by Prof. Svante Pääbo from the Max Planck Institute for Evolutionary Anthropology in Leipzig in 2010.
"The identified Neanderthal gene sequence is almost identical with that of modern humans," Koch stated.
The presence of this receptor in Neanderthals helped them develop immunity to various pathogens and gave them a distinctive “evolutionary advantage,” the researchers believe.
The study was published online in the Journal of Biological Chemistry.