In what could prove to be a setback for an already controversial area of research, scientists say all federally approved lines of embryonic stem cells are contaminated with a non-human molecule.Because the human immune system typically seeks out and destroys cells bearing this molecule, therapies using the contaminated stem cells may fail, explained researcher Dr. Ajit Varki, a specialist in cell biology at the University of California, San Diego."Even worse, in the process of killing the contaminated cells, the patient might have a bad reaction,” Varki explained. “It could be like receiving a bad blood transfusion."The full details of the study are published in the Jan. 23 issue of Nature Medicine after being outlined to a panel of stem cell experts at the National Academies of Science in October.The findings could put the brakes on a type of research already under fire from conservative policymakers in the United States, experts said.
