On Nov. 18, 2025, Stanford Medicine researchers reported that a combination blood stem cell and pancreatic islet cell transplant from an immunologically mismatched donor completely prevented or cured Type 1 diabetes in mice in a study. Type 1 diabetes arises when the immune system mistakenly destroys insulin-producing islet cells in the pancreas.

None of the animals developed graft-versus-host disease — in which the immune system arising from the donated blood stem cells attacks healthy tissue in the recipient — and the destruction of islet cells by the native host immune system was halted. After the transplants, the animals did not require the use of the immune suppressive drugs or insulin for the duration of the six-month experiment.

“The possibility of translating these findings into humans is very exciting,” said Seung K. Kim, MD, PhD, the KM Mulberry Professor and a professor of developmental biology, gerontology, endocrinology and metabolism. “The key steps in our study — which result in animals with a hybrid immune system containing cells from both the donor and the recipient — are already being used in the clinic for other conditions. We believe this approach will be transformative for people with Type 1 diabetes or other autoimmune diseases, as well as for those who need solid organ transplants.

The study builds on the work of the late Samuel Strober, MD, PhD, a professor of immunology and rheumatology, and his colleagues, including study co-author and professor of medicine Judith Shizuru, MD, PhD. They and other Stanford researchers had shown that a bone marrow transplant from a partially immunologically matched human donor allowed formation of a hybrid immune system in the recipient, and subsequent long-term acceptance of a kidney transplant from the same donor. In some cases, Strober and colleagues showed that transplanted donor kidney function lasted for decades, without the need for drugs to suppress rejection.

A blood stem cell transplant can be used to treat cancers of the blood and immune system, such as leukemia and lymphoma. But in those settings, high doses of chemotherapy drugs and radiation needed to treat the cancer and replace the recipient blood and immune system often result in severe side effects. Shizuru and colleagues have devised a safer, gentler avenue to prepare recipients with non-cancerous conditions such as Type 1 diabetes for donor blood stem cell transplantation — knocking their bone marrow back just enough to provide a foothold for the donated blood stem cells to settle in and develop.

Challenges remain using this approach to treat Type 1 diabetes. Pancreatic islets can be obtained only after death of the donor, and the blood stem cells must come from the same person as the islets. It is also unclear whether the number of islet cells typically isolated from one donor would be enough to reverse established Type 1 diabetes.

But, the researchers are working on solutions, which could include generating large numbers of islet cells in the laboratory from pluripotent human stem cells, or finding ways to increase the function and survival of transplanted donor islet cells. The study was published in the Journal of Clinical Investigation.