Contribution of Class III MHC to Susceptibility to Type 1 Diabetes in the NOD Mouse

: A recombinant major histocompatibility complex (MHC) with the same class III region as the NOD mouse, but different class II region from the NOD mouse was identified in the NON mouse, and NOD mice congenic for this recombinant MHC, NOD.NON‐H2, was established. None of the congenic mice homozygous for the NON MHC developed type 1 diabetes, indicating that the NOD MHC is necessary for the development of type 1 diabetes. A small portion of MHC heterozygotes developed late‐onset type 1 diabetes, suggesting the contribution of class III MHC to type 1 diabetes susceptibility.