Pathogens maketh man
7 January 2004 9:00 GMT
by Jane Bradbury

The infectious activity of pathogens over the centuries has left an
indelible mark on the human genome, report evolutionary biologists.
Now, protection that evolved against pathogens that blighted human
populations hundreds of years ago appears to have evolved into protection
against more recent arrivals, such as HIV.

Researchers at Duke University in Durham, North Carolina have found that
infection throughout history may have driven the selection of a single
nucleotide polymorphism in the promoter of the gene encoding the cytokine
interleukin 4 (IL-4).

Gene variants like this that regulate the expression of genes particularly
interest Duke evolutionary biologist Matthew Rockman. Many of them are
present at varying frequencies in different human populations, he explains.
"As evolutionary biologists, we want to understand how these different
frequencies arise."

High IL-4 expression, which shifts T-cells towards the so-called Th2
phenotype and induces B cells to secrete IgE, is associated with allergies
and some respiratory infections. Nevertheless, the -524T allele of IL-4,
which increases IL-4 expression threefold compared with the -524C allele, is
common in some human populations.

Read the rest at BioMedNet
http://gateways.bmn.com/news/story?day=040108&story=1

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