In type 1 diabetes, autoreactive T-cells attack insulin-producing islet cells in the pancreas (frame 1). Fiorina and colleagues showed that the network of genetic regulatory factors controlling production of a protein called PD-L1 is altered in blood stem cells from diabetic mice and humans. They then showed that PD-L1 production could be stimulated by treating blood stem cells with gene therapy or with small molecules (frame 2). The treated stem cells, now bearing PD-L1, home to the pancreas (frame 3), where they bind to the autoreactive T-cells, rendering them harmless (frame 4). In a mouse model, this reverses type 1 diabetes.