Autoimmunity in HLA-DQ8 transgenic mice expressing granulocyte/macrophage-colony stimulating factor in the beta cells of islets of langerhans

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Abstract
Type 1 diabetes (T1D) is a polygenic autoimmune disease with a strong HLA association particularly, HLA-DQ8. We investigated whether islet-specific expression of granulocyte/macrophage colony-stimulating factor (Ins.GM-CSF) in Aß°.NOD.DQ8 mice (HLA-DQ8 transgenic mice on a NOD background lacking endogenous mouse MHC class II molecules) would predispose to development of spontaneous autoimmune diabetes. Aß°.NOD.DQ8 mice expressing GM-CSF in the pancreatic ß cells (8+ G+) as well as litter mates lacking either HLA-DQ8 (8 − G+) or GM-CSF (8+ G − ) or both (8 − G − ) exhibited insulitis and sialadenitis of varying degrees. But none of the mice progressed to develop T1D. Other than the marked mononuclear cell infiltration in livers of mice expressing GM-CSF irrespective of HLA-DQ8 expression (8+ G+ or 8 − G+), no other changes were observed in the animals. Thus, we have shown for the first time that expression of HLA-DQ8 in the diabetes-predisposing mileu of NOD genetic background is not sufficient to predispose to development of autoimmune diabetes even when the potent immunostimulatory cytokine, GM-CSF is expressed in the pancreatic islets.