Thus, both ICOSL−/−CIITA−/− and ICOSL−/−β2m−/− NOD mice were protected from diabetes, but only ICOSL−/−CIITA−/− NOD mice were protected from neuromuscular autoimmunity, confirming the major pathogenic role of CD4+ T-cells in the neuromuscular model. The gene discussed is ICOSLG; the disease is diabetes mellitus.