MHC expression is required for protection in addition to IL-4 secretion. (A) Class I and class II MHC expression on DCs from normal or MHC−/− NOD mice. (B) Similar expression of CD11c, CD40 and transduction efficiency in DCs from normal or MHC−/− NOD mice. (C) Incidence of diabetes after IV treatment of 12-wk old prediabetic female NOD mice with either PBS, DC/IL-4 or MHC−/− DC/IL-4 (7.5x105 GFP+ DCs/mouse). Statistical analysis (Log Rank test): PBS vs DC/IL-4, p=0.02; PBS vs MHC−/− DC/IL-4, p=0.6; MHC−/− DC/IL-4 vs DC/IL-4, p=0.05.