Black Death genetics
The genes on the list have a variety of functions. One gene, SLC45A2, is known to be involved in skin pigmentation. Others are linked to immune-system function.
One immune-related cluster included three altered genes, making it the most obvious candidate for closer perusal. The cluster, called TLR2, was already known to be involved in building the receptors on the surface of leukocytes, immune cells that recognize and destroy foreign invaders.
Because plague was such a widespread and devastating event in Europe, Netea and his colleagues reasoned that the Black Death outbreak, which occurred after the Roma arrived, might have put pressure on this gene cluster to evolve.
To test the idea, they looked at how cells engineered to express TLR2 would hold up against Y. pestis and Yersinia pseudotuberculosis, an ancestor of Y. pestis. They found that TLR2 caused a heightened immune response when exposed to both bacteria.
Other diseases could have altered the same genes, Netea said, but plague is a strong candidate, because it affected Europe and not northwest India, and because it had such a widespread, devastating influence. The findings could have medical implications even in today's world, where plague is no longer such a danger. For example, autoimmune disorders, in which the body attacks its own tissues, may arise because of immune systems programmed by epidemics to respond strongly to the threat of invasion, Netea said.
Humans "were modified, basically, by the infections," he said.
The researchers report their findings today (Feb. 3) in the journal Proceedings of the National Academy of Sciences.
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