Human to Human (allotransplantation):Transplantable organs include: heart, liver, kidneys, lungs, pancreas, and thymus.
Transplantable tissues include: Bone, skin, corneas, heart valves, intestines, veins, and tendons.
Animal to Human (xenotransplantation):Insulin-producing pig cells, wrapped in seaweed to avoid immune attack, have been tested on human diabetics in Russia.
The results were encouraging, and the procedure is approved for sale in Russia. However, it will probably be some time before other countries approve this, or any xenograft procedures.
Dangers of xenotransplantation:
Heightened risk of rejection of organs, tissues, and cells, and vascular rejection.
Significant risks of disease, especially of retro (ancient) viruses, to the recipients.
Religious objections.
Ethical issues: risk of genetic alteration of the animal organs and tissues.