Transplantations: Allotransplantation and Xenotransplantation

Xenotransplantation involves the donation of cells, tissue, organs, or body parts from one species to a recipient of another species. The tissue (graft) collected from the donor is called the xenograft. Xenotransplantation has been proposed because of the gap between the number of human donors and the number of people on the waiting list for transplants.

Pigs have been proposed as the animals of choice for providing xenografts to humans. Research focuses primarily on the heart, but also on the kidneys and the islet cells of the pancreas. Some advantages of using pigs are that pig organs are similar in size to human organs, they have large litters (up to 12 piglets), and can be housed in sterile, controlled environments to decrease the chance of disease being transferred to the human recipient.

Due to being more closely genetically related, nonhuman primates were considered and attempted for xenotransplantation in humans. However, ethical concerns, a greater risk of disease transfer to humans, and the greater difficulty in the confinement of nonhuman primates resulted in certain governments, such as the UK, banning nonhuman primates as candidates for transplantation.

An allograft is a tissue that is being transplanted from one individual to another individual of the same species. For example, a liver from one individual is the allograft that is donated to the recipient in an allotransplantation.

An autograft is tissue that is taken from one part of an individual's body and placed in a different location on the same individual. Since this tissue is genetically identical, the immune system will not reject the graft. Examples of autografts include skin, blood vessels, bone, and bone marrow. The most common autograft is skin. The patient's skin may have been damaged by burns, injury, disease, or infection. Healthy tissue from the individual will be collected from areas such as the back, abdomen, or inner thigh. The surgeon will overlay the healthy tissue over the damaged area of the skin and apply staples or stitches to secure the graft. A dressing will be applied to protect the area. The patient will be advised to keep the area clean, refrain from heavy activity, and take medication to manage the pain. The area the graft was taken from usually heals more quickly than the area with the new graft. Sometimes, the first graft will not adhere properly and a second graft is required.

Allograft vs Autograft

An allograft is tissue transplanted from an individual of the same species while an autograft is a tissue transplanted from one part of an individual's body to another.

If the patient has torn their anterior cruciate ligament (ACL), surgery might be recommended to repair the damage. There are advantages and disadvantages to using allografts or autografts. An allograft would involve transplanting a tendon from a deceased donor. With an allograft, there might be a quicker recovery time, due to needing only one incision in the recipient, but rejection and infection from the donated tissue are a possibility.

Transplantation is the surgical transfer of cells, tissue, organs, or body parts from one place to another. Allotransplantation is the transfer of cells, tissues, organs, or body parts from one individual of the species to the same or another individual of the same species. The most common allotransplantations are liver, kidney, and heart. The species involved does not need to be human. For example, transplantation of dog kidneys has been successfully performed. The donor does not need to be deceased to donate a graft. Kidney transplants can be given by a living donor, both the donor and recipient will each have a fully functional kidney. . Xenotransplantation involves the transfer of cells, tissues, organs, or body parts from a member of one species to a member of another species. So far, we haven't had a successful xenotransplantation into a human.