Researchers at Stanford University Medical School have reported what appears to be the first significant use of monoclonal antibodies to help transplant tissues in animals.

Transplant patients often have trouble incorporating foreign tissues into their bodies, and doctors have had to rely on powerful and often dangerous drugs to keep bodies from rejecting the transplants. If the Stanford discovery eventually helps humans overcome the rejection problem, it would make transplants much safer.

"This is an exciting model because we were able to create a tolerance in the animals with one course of monoclonal antibodies and no other drug treatment," said Dr. C. Garrison Fathman, associate professor of medicine at Stanford.

The experiments were conducted on mice in Fathman's laboratory, and results were published in the July 17 issue of Science.

Monoclonal antibodies -- proteins made by the immune system to fight disease -- in the past have helped control kidney transplant rejection. But this apparently is the first time that, when given to live animals, they have induced a "tolerance," or permanent truce between the animal's immune system and the tissues it wants to attack.

Fathman said his group soon will test the method in primates, but human tests are several years away. In the Science article, Fathman and his colleagues describe how they cured diabetic mice with injections of insulin-producing cells from healthy mice.

The technique, conceived by Dr. Paul Lacy at Washington University in St. Louis, is in essence a tissue transplant because the donated cells take up permanent residence in the recipient's liver. The transplanted cells secrete insulin into the bloodstream, restoring normal blood sugar levels to diabetics.

But in the past that process, tested in humans and animals, has been limited in its success because the immune system is trained to attack and destroy foreign substances.

To control that rejection, powerful drugs must be administered to suppress the immune system. But the drugs are expensive and cause many complications.

The new Stanford approach permits long-term tolerance for foreign substances without the use of drugs. It works by killing the recipient's supply of "helper" T lymphocytes, the type of white blood cell responsible for rejection.

The scientists believe that when the cells eventually grow back they are unable to recognize that the implanted tissue is foreign.