Stem cells prevent transplant rejection

Cells derived from embryonic stem cells have been used to prevent the rejection of transplanted organs in mice, report researchers from the University of Iowa and Chang Gung University College of Medicine, Taiwan.

Nicholas Zavazava and colleagues treated mouse embryonic stem cells with growth factors to transform them into blood stem cells, which express very low levels of so-called "transplantation antigens", thus protecting them from immunological rejection.

The donor blood stem cells were then injected into the recipient mouse, where the stem cells found their way into the recipient mouse's thymus and went on to develop into T-cells. Tests suggest that the recipient mouse's T-cells learned to recognize the donor blood stem cells as host cells, thus enabling the donor cells to circulate freely within the recipient mouse's blood. The researchers then implanted the donor mouse's heart into the recipient mouse. The heart was not rejected because the recipient mouse's immune system recognized it as being compatible.

If the technique is found to be successful in humans it will solve many of the problems surrounding organ transplantation, for example, it would remove the need for patients to take immunosuppressive anti-rejection drugs, whilst also preventing the sometimes fatal graft-versus-host disease.

Bonde S, Chan K-M, Zavazava N. ES-Cell Derived Hematopoietic Cells Induce Transplantation Tolerance. PLoS ONE. 2008;3:e3212. doi:10.1371/journal.pone.0003212.