Since the first kidney transplant in 1950 and the first heart transplant in 1967 the field of transplant immunology has grown by leaps and bounds.  As successful as transplant medicine has become, there is still a major problem:  not enough donors.  This has led many scientists to explore the field of

xenotransplantation, using non-human animals as a source for organs. 

Other than the circumstance of receiving an organ from an identical twin, human to human transplants require immunosuppressive therapy to prevent immune rejection from occurring.  As good as this therapy has become, long-term rejection still occurs. 

Current research, therefore, centers on two areas:  genetics and immunology.  The genetic aspect involves genetically engineering the donor animal.  Two already successful inroads to this end are producing chimeras and immune cloaking.  A chimera is a genetically modified animal that expresses human antigens.  Immune cloaking involves a process that “hides” the animal antigens from immune scrutiny.  These techniques have been proven to work in animal models allowing rat pancreas to be transplanted into a mouse.  So, the future of human health may lie with our porcine and bovine brethren.