For example, pigs harbour endogenous retroviruses that can infect human cells. Scientists have identified infectious viruses in the blood plasma of pigs. Also, the recipient's DNA could interact with viral DNA, to create new and even deadlier viruses (Windsor 23). The patient receiving the organ could also suffer a more severe implant reaction since the organ is not human (Melo 431). The unsuccessful use of xenotransplantation raises concerns regarding the potential infection of recipients. For example, Simian Immunodeficiency Virus (SIV) is common in many African monkeys and does not cause disease in some species. However, it is widely accepted that SIV was transmitted to humans where it mutated into the Human Immunodeficiency Virus (HIV), causing the worldwide AIDS pandemic. HIV is a retrovirus that many researchers believe was transmitted to humans from monkeys. (Windsor 24) Recent outbreaks of the Ebola Virus have crossed into humans from monkeys and reached fatality rates as high as 88 percent. (Windsor 25) There is no guaranteed way to eliminate the infectious deadly viruses that may cause a global health catastrophe.
Secondly, the human body's immune system is vigilant against foreign invaders. The body has a unique protein-based 'tissue type', shown in our blood and on the surface of all our cells. Any part transferred to another person, whether blood or an organ, will be recognised as foreign by the recipient's body. The immune system may attack it, leading to rejection; this can happen very quickly. The body's immune system is designed to recognise pathogenic organisms and eliminate them. The same response causes rejection of transplanted tissues if the tissues are not extremely well matched. All rejection can be prevented by suppressing the immune response, as people who have had a transplant are prescribed to take immunosuppressive drugs. While these drugs are often successful, they leave the patient vulnerable to many infections.
