Allogeneic stem cells, clinical transplantation and the origins of regenerative medicine.

The therapeutic use of stem cells is a popular topic that is often in the news. Stem cells are of particular relevance to the transplant community, as stem cell-based therapies will probably be derived from allogeneic sources. Stem cells may be obtained from somatic (adult) cell or embryonic cell origin. The ability to establish stem cell lines in vitro means that we can standardize therapeutic grafting applications, which is a prerequisite for the widespread application of stem cell therapy. This attribute also means that we can produce large batches of allogeneic terminally differentiated cells, which can be administered to patients. Three important barriers to the deployment of this therapy currently exist; in addition to the many ethical issues facing the widespread use of stem cell therapy, it is also important to develop methods to derive pure terminally differentiated cells for transplantation and to induce immune tolerance to these allogeneic cells, as daily anti-rejection therapy cannot be justified for many potential applications.