Rejection Hurts

A new study published in Nature is giving researchers pause as they consider the usefulness of induced pluripotent stem cells in treating disease, says The New York Times' Andrew Pollack. The study reports that tissues made from iPS cells may be rejected by a patient's immune system — even tissues derived from cells from the same patient, Pollack says. Although it is unclear whether these results from mice will hold true in humans, experts say they are nonetheless surprised, and that it will now be more difficult to take stem cells to the clinic. The University of California, San Diego, researchers who conducted the study found no immune response to implanted embryonic stem cells, but their immune systems "attacked" iPS cells, Pollack says. "Further experiments suggested that the reaction was caused by the abnormal activation of certain genes in the iPS cells, resulting in the production of proteins that seemed foreign to the immune systems of the mice," he adds.