Deviation of islet autoreactivity to cryptic epitopes protects NOD mice from diabetes.

To better understand loss of self-tolerance in diabetes-prone NOD mice, we are generating ICA69 transgenes under control of the tetracycline-regulated tet07 minimal promoter. In vitro pilot studies showed leaky transgene expression, but addition of beta-globin genomic insulator flanks prevented leakage and dramatically enhanced transgene expression even in transient transfection, with excellent suppression by Doxycycline. In vivo, the accidental loss of insulator flanks during transgene insertion in one transgenic NOD founder, tet1, re-established leakiness with high level, exclusive ICA69-transgene expression in stromal elements of thymus and spleen.

Autoimmune islet destruction in spontaneous type 1 diabetes is not beta-cell exclusive.

Pancreatic islets of Langerhans are enveloped by peri-islet Schwann cells (pSC), which express glial fibrillary acidic protein (GFAP) and S100beta. pSC-autoreactive T- and B-cell responses arise in 3- to 4-week-old diabetes-prone non-obese diabetic (NOD) mice, followed by progressive pSC destruction before detectable beta-cell death. Humans with probable prediabetes generate similar autoreactivities, and autoantibodies in islet-cell autoantibody (lCA) -positive sera co-localize to pSC.