One problem that arises when the donor and recipient belong to different species is that the transplanted organ is rejected by the recipient’s immune system. Indeed, the human immune system is generally activated when a foreign entity is detected in the body. The immune system helps, for instance, to fight off invading organisms such as bacteria and viruses. In the case of a xenotransplant, the transplanted cells are recognised as non-self (unfamiliar) ultimately leading the immune system to elicit an immune response to eliminate them. As far as transplanting pig organs into primates is concerned, the four immunological barriers to overcome are: hyperacute rejection, acute humoral xenograft rejection, cellular rejection and chronic rejection. At this stage, with the progress achieved in this field in the last ten years, hyperactute rejection has been overcome and scientist are trying to prevent the onset of acute humoural xenograft rejection.
Another risk of xenotransplantation could be cross-species transmission of undetected or unidentified animal infectious agents to patients that could, in turn, be transmitted to the general public. The potential risk of cross-species infection is also facilitated by the use of immunosuppressive agents indispensable for transplantation. |