Diabetic mouse incorrectly typed.

In our report "Three recessive loci required for insulin-dependent diabetes in nonobese diabetic mice" (1), we outcrossed diabetes-susceptible strain NOD mice with diabetes-resistant strain NON, backcrossed the resistant F1 hybrids to the susceptible NOD parental strain, and analyzed segregation of diabetogenic genes. We reported that 1 of 19 mice developing diabetes at first backcross apparently exhibited recombination within the major histocompatibility complex (MHC) on chromosome 17. Microcytotoxicity testing of splenic leukocytes with monoclonal antibodies and complement indicated homozygosity for the H-2Kd allele (NOD type), but expression of I-Ek (NON type). Since a recessive diabetogenic allele (Idd-lS) tightly linked to MHC was