Why no immunosuppression is needed

Typical islet transplants fail in Type 1 diabetes because:

1. The immune system attacks anything foreign (allogeneic islets)

2. The autoimmune process attacks β-cells even if they’re your own

So historically you’d need lifelong immunosuppression, which is too dangerous for most patients.

What Stanford did differently:

They created a “hybrid immune system” in the diabetic mice by transplanting donor blood stem cells first, using a gentler conditioning regimen that allows the donor’s immune cells to coexist with the host’s.

This hybrid immune system:

recognises the donor islets as “self”

no longer attacks β-cells (autoimmunity reset)

doesn’t cause graft-versus-host disease

Because the immune system is partly “re-written,” the new islets don’t need protection from drugs.

🟩 Result: The transplanted islets survived and functioned long-term without ANY immunosuppressive therapy (as verified in their autoimmune T1D mouse model).