A xenotransplant is a transplant between species (animal to human). This means that living cells, tissues, and/or organs are transferred from one species to another.
             The ideal animal to use, in an animal-to-human, xenotransplant would be the chimpanzee, because their genome is more than 98 percent identical to the human genome. But chimpanzees are an endangered species, are too costly to raise, they are slow to mature, and there is the possibility that they may harbor viruses that may be fatal to humans. With chimps out of the question, the next choice of animal is the pig. Their organs are a very similar size of that of a human, they have large litters and can be raised in a sterile environment to reduce the likelihood of transmission of disease to humans. Although there is always the worry of viruses that are part of the animal's genome and cannot be removed. Pigs have already been used to treat humans, for example as a souse of heart valves for people with damaged hearts. This however is quite different from xenotransplants because the heart valves are treated with special chemicals that kill the cells and destroy potentially dangerous agents, these do not pose the same risks as transplants of living pig cells and organs.
             The first successful xenotransplant was in 1995. A man named Jeff Getty was infected with HIV and had AIDS. Baboon bone marrow was transplanted into him in hopes to replace his crumbling immune system with an HIV-proof baboon immune system to protect him from the infection. The baboon cells only functioned for two weeks, but Getty is still alive and the researchers learned a great deal.
             • Xenotransplants could potentially provide an unlimited supply of organs, cells, and tissue, for treating human disease. About 4000 people die each year waiting for organ transplants. Any disease that is treated by human-to-human transplants could potentially be treated by xenotransplantation.
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