But a great deal has changed in a year and a half. In short, the choice between medical progress and moral principle is a false dilemma. We can pursue the cure of disease in morally acceptable ways. As a consequence of further research it is clear that many irresponsible claims about the unique promise of embryonic stem cells must now be abandoned. Stem cells cannot be found in most adult tissues.
Embryonic cells are less likely to be rejected by the body's immune system.
The cells most fully protected from such rejection are a patient's own stem cells, which can be modified, stimulated, or grown in culture to repair damaged tissue. Because any foreign tissue, even embryonic cells, may lead to incompatible transplants, some embryo research proponents such as the Geron Corporation are moving toward the further abuse of making genetically matched embryos for each patient by cloning. Dr. Micheline Mathews of Harvard Medical School has cured a rare genetic disease in mice by inserting the missing gene into their own stem cells. Adult cells may produce formless tissue, but only embryonic cells can be used to create whole organs. Adult stem cells are vastly more versatile than once thought.