Initially, primates seemed to be a hopeful choice for this process because their immune systems are most similar to humans, but there are a number of disadvantages with using an animal so closely related to humans. Even though both animals are about the right size for humans, there are more ethical concerns when using a primate which is intelligent and interacts in a social unit. Primates have a long breeding process and they have never been reproduced in large quantities for human exploitation. Finally, it is easier for the public to accept using pigs in xenotransplantation because they do not exhibit human traits. There are many advantages to understanding and using animal organs for transplantation.
Xenotransplantation offers hope of an immense supply of organs available for transplantation.
With this large supply of organs, recipients could plan their surgery rather than have the procedure done only when an organ becomes available. The differences among species in their disease resistance capabilities could be useful for transplantation. Finally, the Institute of Medicine, and the Food and Drug Administration both recognize the benefits of research on xenotransplantation, but they call for precautions and guidelines for testing and research due to medical and ethical concerns. These medical and ethical problems have the potential to effect both the individual patient as well as the general population. The spread of new or existing infectious diseases into the human population, and the compatibility of the human and animal organs are medical concerns stemming from xenotransplantation.