Mandelkow, E. 1999. The Tangled Tale of Tau. Nature, Volume 402. Newsweek, January 31, 2000. Because of the high demand for whole organ transplants, research scientists in academia and in pharmaceutical companies are investigating xenotransplantation, the grafting of organs and tissue from one species to another.
Scientists are particularly interested in the pig as an organ donor.
The pig is similar enough to humans of justify hope that the transplants will ultimately be successful, is different enough from humans to make disease transmission less of a problem, and can be raise quickly and efficently by well-tried modern agricultural methods. Serious obstacles remain before humans will be able to receive pig organs as replacements, however, including cross-species immunological barriers to such graft, and the threat of some unforeseen disease transmission which could prove disastrous to humans. Hyperacute rejection results from the presence of antibodies in humans to a certain carbohydrate expressed on the lining of pig blood vessels. The complement system participates in hyperacute reactions. Genetically-engineered pigs have been developed which express a protein that regulates complement and thus blocks hyperacute rejection.