Why is xenotransplantation being considered?
Transplantation between members of the same species is known as allotransplantation, and in humans this is a very successful way to treat a variety of illnesses. However, few human tissues, cells or organs are available for transplantation, so that many patients who could benefit from a transplant wait in vain for a suitable donor. Transplant specialists are therefore considering animals as possible donors for human transplantation. The greatest benefit of animal-to-human transplantation would be a potentially unlimited supply of cells and tissues for use in humans. Organ transplants are the most complicated type of xenotransplantation because unlike cells and tissues, organs require lots of blood vessels to supply the organ with oxygen and nutrients. Some researchers are looking at temporarily transplanting pig livers into humans who have liver failure. Some patients with liver failure need to undergo urgent liver transplants, usually within 24 to 36 hours. If a compatible human liver
