The findings are reported in the June 7 issue of Current Biology by Dr. Franck Prugnolle and colleagues at the University of Cambridge.
HLA class I proteins are critical players in the recognition of antigens--bits of foreign protein derived from invading pathogens--and in the presentation of the antigens on the surfaces of cells. HLA proteins and the antigens they present are recognized by specialized immune cells, resulting in immune responses that combat disease. But why should HLA genes be so diverse? Numerous factors could contribute, but a leading idea has been that pathogens themselves play a role. Past work had offered clues to this effect--for example, individuals with some HLA genotypes are more susceptible (or more resistant) to some pathogens than others. If different versions of HLA proteins can influence how the immune system deals with a particular pathogen, it follows that, in theory, HLA genes should evolve to deal most effectively with the various antigens humans encounter.
This kind of evolution, leading to diverse HLA genotypes in which individuals possess two different versions, or alleles, of the various HLA genes, forms the basis for the idea of "pathogen-driven balancing selection," or PDBS.
In their new work, the researchers set out to test the PDBS hypothesi
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Contact: Heidi Hardman
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Cell Press
6-Jun-2005