GAD2 and diabetes mellitus: We show here that a class II-restricted epitope of GAD65, a key autoantigen involved in type 1 diabetes pathogenesis (9, 10), administered by direct immunization to female NOD mice inhibits the development of diabetes (83% in untreated mice versus 57% in CCGAD65-treated mice) and reduces insulitis in association with induction of antigen-specific cCD4+ T cells.