of autoimmunity in NOD mice. NOD mice have a mutation in exon 2 of the CTLA-4 gene, which causes it to be spliced incorrectly. CTLA-4 plays a major role in suppressing the T-cell immune response. Without the proper functioning of CTLA-4, T-cells attack the insulin producing cells. This results in Type 1 Diabetes. References Laboratory mouse strains Diabetes Population genetics