In a setback for medical research in the United States, researchers have announced that all the country’s federally approved lines of human embryonic stem cells are contaminated with a molecule from mice. If eventually used for patient therapies, they could provoke an immune reaction that would destroy their ability to deliver hoped-for cures for diseases such as Parkinson’s, Alzheimer’s and diabetes.

The research finding was reported yesterday in the journal “Nature Medicine.” And it turns up the heat on the Bush administration’s policy of providing federal funding only for research using specific embryonic stem cell lines created before August 2001.

Fred Gage, professor of genetics at the Salk Institute for Biological Studies in La Jolla, California and co-author of the study, explains how the stem cell lines came to be contaminated in the first place.

Guests:

Fred Gage, professor of genetics at the Salk Institute, who co-wrote the paper on the stem cell findings in the current issue of Nature Magazine.