The diabetes-prone NZO/HILt strain. I. Immunophenotypic comparison to the related NZB/BINJ and NZW/LacJ strains

New Zealand Obese (NZO)/HILt male mice exhibit a polygenic obesity and approximately 50% develop type 2 diabetes. This strain is known to produce a variety of autoantibodies, including autoantibodies to the insulin receptor. Because of their relatedness to the autoimmune-predisposed New Zealand Black (NZB) and New Zealand White (NZW) inbred strains, we compared NZO to its two related strains for shared hematologic and immunologic characteristics. Comparison of the three strains by serotyping and genotyping methods indicated that NZO shared with NZW the rare (recombinant) H2(z) haplotype at the major histocompatibility complex. Similar to the NZB and NZW strains, spleens from NZO mice contained increased numbers of CD19(+)CD43(+) IgM(-) B-1 B cells, a phenotype associated with natural autoantibody production. NZO mice developed a progressive microcytic anemia that was distinguished from NZB hemolytic anemia by absence of demonstrable antierythrocyte antibodies in the former. Outcross of NZO females with NZB males accelerated development of obesity and diabetes in F1 males. NZO males made B-lymphocyte-deficient by a disrupted immunoglobulin heavy chain gene did not become diabetic. These results suggest that NZO mice should be useful to investigators interested in studying the genetic contributions to autoimmunity made by the related NZW and NZB strains. Further, these results, combined with the pancreatic histopathology contained in the companion manuscript, suggest that B lymphocytes may be important contributors to diabetes pathogenesis in the NZO mouse.