Page 1113 - Veterinary Immunology, 10th Edition

obtained from a donor who is usually unrelated to the graft
VetBooks.ir recipient. Because the major histocompatibility complex (MHC) and

blood group molecules on the allograft are different from those of
their host, allografts induce a strong immune response that causes

graft rejection. This rejection process must be suppressed if the
grafted organ is to survive.
Xenografts are organ grafts transplanted between animals of
different species. Thus the transplant of a pig liver into a human is a

xenograft. Xenografted tissues differ from their host both
biochemically and immunologically. As a result, they provoke a
rapid, intense rejection response that is very difficult to suppress.
Clinical grafting in domestic animals is a recent procedure.

However, renal allografting is now routine in dogs and cats, and
bone marrow allografts promise to be very useful in some forms of
tumor therapy. Most current organ grafts are obtained from healthy
donor animals. This raises ethical issues as to whether it is

appropriate to subject a donor animal to major surgery in order to
provide an organ for another animal. Although the benefits of
allografting to the recipient are obvious, it is unclear how the donor
animal might benefit. Unlike human donors driven by altruism, an

animal donor is given no choice in the matter. It is possible,
however, to justify organ donation if thereby an animal would be
saved from inevitable euthanasia and if the donor could be
provided with a good home. For this reason, many animal

transplantation centers require that the donor animal be adopted
and cared for by the owner of the recipient animal.

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