Mouse to Primate XenoStem Transplant

Saint-Mande, France -

The ability of various stem cell types to be immune privileged is well known. For example, it is known that mesenchymal stem cells can act as veto cells under specific conditions.

While mesenchymal stem cells are derived usually from the bone marrow, and it would make sense for them to suppress immune hyperactivation since immune response in the marrow has detrimental effects to hematopoiesis, there is no real scientific reason for why embryonic stem cells should be immune privileged. Despite this, numerous groups in the field hold the wishful belief that embryonic stem cells would be able to survive in an allogeneic, or even xenogeneic environment without immune suppression. While this belief is wrong, what is even wronger, is using non-appropriate experiments to demonstrate lack of immune privilege.

A recent paper (Bonnevie L et al. Is Xenotransplantation of Embryonic Stem Cells a Realistic Option? Transplantation. 2007: 83(3):333-335) is making the case that embryonic stem cells can not be used xenogeneically due to immune mediated destruction. Although the notion of xenogeneic transplantation is interesting, the investigators made several mistakes. Firstly, they transplanted mouse ES cells into baboons. Since baboons have high levels of preformed antibodies to cells from lower level animals, the hyperacute rejections should instantly clear the transplanted cells. Accordingly, the fact that the investigators in the paper did not witness any therapeutic effects in the myocardial infarct model, using mouse embryonic stem cells should not be surprising.

Unfortunately, good immunology experiments are lacking in the field of stemcellology !