A carbohydrate-containing antigen, termed Pk blood group which is distinct from the well known ABO and Rh blood grouping systems, is present at variable levels on the surface of white and red blood cells in the general population.
Their study shows that cells from rare individuals ( 1 in a million) who produce excess of this blood group antigen have dramatically reduced sensitivity to HIV infection.
Conversely, another slightly more common subgroup of people who do not produce any Pk ( 5 in a million) was found to be much more susceptible to the virus. "This study is not suggesting that your blood type alone determines if you will get HIV. However, it does suggest that individuals who are exposed to the virus, may be helped or hindered by their blood status in fighting the infection," said lead author Dr Don Branch of Canadian Blood Services.
Increasing the level of the Pk antigen in cells in the laboratory also resulted in heightened resistance to HIV, while lowering it increased susceptibility.
"This discovery implicates the Pk level as a new risk factor for HIV infection and demonstrates the importance of blood-group-related science," said Dr Olsson. The study is published in Blood, which is currently available online.&13;