A biological trick that deceives the immune system may one day make it possible to cure diabetes with the transplantation of insulin-producing pig cells, a Harvard Medical School researcher says.
Dr. Denise Faustman reports in Friday's edition of the journal Science that she and her team have developed a way to transplant cells, and perhaps whole organs, from one species to another without having to use drugs to block rejection by the immune system of the recipient.She proved the technique by successfully transplanting human insulin-making cells into laboratory mice.
"We did it without having to treat the mice with drugs to prevent rejection of the cells," said Faustman. "This has a major advantage over the current way of transplantation where the whole immune system has to be suppressed with drugs. We're treating the tissue, not the patient."
Faustman said the trick is in hiding the presence of foreign tissue from lymphocytes, which are the patrolling cells of the immune system.
The lymphocytes, the white cells in the blood, seek out antigens on the surface of foreign tissue. When the white cells find these antigens, they attack by coating the cells with antibodies and calling in other lymphocytes. This starts the rejection process.
"What we've done is make it so the lymphocytes can't recognize the antigens," said Faustman.
This is done by coating the foreign cells with a modified antibody before the cells are transplanted into the recipient.
In the mouse experiment, Faustman and her team got human pancreatic islets, cells that produce insulin, and immersed them in a solution of the modified antibodies. The antibodies blocked the foreign tissue antigens that normally would be spotted by the white blood cells.
The treated human cells were then inserted into the kidneys of 40 laboratory mice. A similar number of mice received untreated human pancreatic islets.