By Brandon Keim November 26, 2007
With the help of an ingenious protein hack, scientists have used stem cells to grow new immune systems in mice -- a technique that could someday treat human autoimmune diseases.
In a study published in Science, Stanford University researchers described how blood-forming stem cells generated new immune systems when injected into mouse bone marrow. That wasn't particularly surprising; the real breakthrough took place before the stem cell injections, when the researchers erased the old immune systems.
Traditionally, this is done with radiation and chemicals that also destroy surrounding tissue and sometimes cause brain damage, infertility or cancer. Instead of these scorched-earth therapies, the Stanford scientists gave the mice an antibody designed to neutralize existing blood-forming, or hemapoietic, stem cells. Hematopoietic cells are the building blocks of the immune system; with the old cells out of the way, the researchers added new ones, then sat back and watched fresh immune systems grow.
Duplicating this feat in humans is the holy grail of treatments for for autoimmune diseases, in which bodies are attacked by their own defense systems. But before that happens, more mouse work needs to be finished. The Stanford mice were engineered to possess non-functioning immune systems: they had the necessary components, but the system wasn't on-line.
The researchers must next make their technique work in fully functional mice. Then they need to figure out how to design human-specific antibodies, as the mouse antibodies targeted proteins not present in our own cells.
But if they can do this, the ramifications are enormous: an estimated 20 million Americans suffer from autoimmune diseases, including type 1 diabetes, arthritis and multiple sclerosis. Many other conditions, including chronic fatigue syndrome and obesity, are suspected of having an autoimmune component.
