|MadSci Network: Medicine|
Your question is both an interesting and a timely one. The primary side-effect of concern with xenotransplantation is the risk of rejection, which is considerably higher than with human organ transplants. This is due to a number of reasons, but mostly because of differences in the major histocompatibility antigens and blood group antigens. Rejection can be controlled by immunosuppressive drugs, but the person would have to take these drugs for the rest of their lives - leaving them very susceptible to infection much like an AIDS patient. The second area of concern is the risk of disease. Pigs & baboons, the leading 'candidates' for xenotransplants into humans, carry a number of diseases that could potentially infect humans. In fact, one pig retrovirus has already been shown to have infect a human recipient of a pig organ. The danger here is the potential development of another virus like HIV, or perhaps even something worse. Those in favor feel that they can successfully screen for such viruses, but you can't screen for a virus you don't know exists. Beyond those two issues, however, the question of how an animal organ functions in a human body has not been that well examined. Species are different genetically, and their responses to stimuli and stress are (as a result) very different. I've included some links below that can provide additional information that can answer your question. These are all science links, and provide a considerable amount of information both for and against xenotransplants. http://www.cdc.gov/ncidod/EID/vol2no1/michler.htm http://xenotransplant.ineu.org/xenotrans/online.htm http://www.nature.com/nm/web_specials/xeno/
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