Because the onset of type 1 diabetes is characterised by the presence of autoantibodies against GAD65 and insulin in most HLA-DR3-DQ2 humans, sera of mice were tested for antibodies against murine 30-mer peptides that span the length of murine proinsulin-2, the isoform most similar to human proinsulin, and against human GAD65, which has over 95% sequence homology with the murine equivalent. The gene discussed is GAD2; the disease is type 1 diabetes mellitus.