Current status of animal-to-human transplantation.

The transplantation of animal organs into humans as a way of treating organ failure has been pursued for 100 years. Clinical xenotransplantation, as such, has always failed because the transplanted organ is rejected by the recipient. Recent advances in transplant immunology have revealed some mechanisms underlying the rejection of xenografts, and these discoveries have sparked efforts to use genetic engineering of animals and therapeutics directed at the recipient to overcome this problem. This paper reviews the current understanding of the mechanisms of xenograft rejection and efforts to overcome rejection and other hurdles.