A similar controversy over self versus non-self cells is gaining momentum among embryonic stem (ES) cell researchers, but in this case the evidence favours autologous cells. In recent work, researchers made the first successful autologous grafts to alleviate a mouse model of Parkinson's disease using ES cells1. The ES cells were derived in the usual way from mouse blastocysts made by nuclear transfer—by removing the nucleus from a mouse egg cell, and infusing it with DNA from the host. ES cells were then harvested from the blastocyst, and differentiated into dopamine-producing cells for grafting.

While making mouse ES cells through nuclear transfer is well established, such cells have never before resulted in grafts that cured a disease. “Nothing in this paper is new,” says Viviane Tabar, a neurosurgeon at the Sloan-Kettering Cancer Center in New York City, and an author of the paper, “everything has been done independently, but this is the first time we made the full story come together.”

After the ES cells differentiated into dopamine-producing neurons, they were transplanted into the brains of 24 Parkinson's mice. While some improvement in behaviour occurred in the control group that received allogeneic grafts, symptoms were completely alleviated in the mice that received autologous grafts. While the allogeneic treatments induced an immune response, the autologous grafts did not trigger the body's defence system at all.

But autologous cells for neural application in humans would be hard to come by. Human ES cells have yet to be created by nuclear transfer, and other techniques to create pluripotent stem cell lines require genetic modifications that prevent their use in therapy.

Besides Pranela Rameshwar of the New Jersey Medical School in Newark warns that autologous grafts could have a downside, as the mutations involved in disease progression will be present in self cells. “It might be safer to use an allogeneic system, despite the immunocompatibility issues,” she says.