Dendritic cells from nonobese diabetic mice exhibit a defect in NF-κB regulation due to a hyperactive IκB kinase

Insulin-dependent diabetes mellitus (IDDM) is characterized by the T cell-mediated destruction of insulin-producing beta cells. Accordingly, APCs, such as macrophage, have also been shown to be important in the disease process. However, the role(s) of dendritic cells (DCs) that exhibit potent APC function remains undefined in IDDM. Here we demonstrate that DCs derived from nonobese diabetic (NOD) mice, a model for IDDM, are more sensitive to various forms of stimulation compared with those from C57BL/6 and BALB/c mice, resulting in increased IL-12 secretion. This property is a consequence of hyperactivation of NF-KB, a transcription factor known to regulate IL-12 gene expression. Specifically, NOD DCs exhibit persistent hyperactivation of both I kappaB kinase and NF kappaB in response to stimuli, in addition to selective degradation of I kappaB epsilon. Transfection of NOD DCs with a modified form of I kappaB alpha significantly reduced IL-12 secretion, suggesting that hyperactivation of NF-kappaB was in part responsible for increased IL-12 production. An enhanced capacity of NOD DCs to secrete IL-12 would be expected to contribute to the development of pathogenic Th1 (Tc1) cells during the diabetogenic response.