Induction of insulin-dependent diabetes mellitus in PVG.RT1u rats

The iddm4 locus segregates with diabetes susceptibility in congenic WF.iddm4 rats

Viral antibody-free BBDR and WF rats never develop spontaneous diabetes. BBDR rats, however, develop autoimmune diabetes after perturbation of the immune system, e.g., by viral infection. We previously identified a disease-susceptibility locus in the BBDR rat, iddm4, which is associated with the development of autoimmune diabetes after treatment with polyinosinic:polycytidylic acid and an antibody that depletes ART2(+) regulatory cells. We have now developed lines of congenic WF.iddm4 rats and report that in an intercross of N5 generation WF.iddm4 rats, approximately 70% of animals either homozygous or heterozygous for the BBDR origin allele of iddm4 became hyperglycemic after treatment to induce diabetes. Fewer than 20% of rats expressing the WF origin allele of iddm4 became diabetic. Testing the progeny of various recombinant N5 WF.iddm4 congenic rats for susceptibility to diabetes suggests that iddm4 is centered on a small segment of chromosome 4 bounded by the proximal marker D4Rat135 and the distal marker D4Got51, an interval of <2.8 cM. The allele at iddm4 has 79% sensitivity and 80% specificity in prediction of diabetes in rats that are segregating for this locus. These characteristics suggest that iddm4 is one of the most powerful non-major histocompatibility complex determinants of susceptibility to autoimmune diabetes described to date.

Thymectomy and radiation-induced type 1 diabetes in nonlymphopenic BB rats

Spontaneous type 1 diabetes in BB rats is dependent on the RT1(u) MHC haplotype and homozygosity for an allele at the Lyp locus, which is responsible for a peripheral T-lymphopenia. Genetic studies have shown that there are other, as yet unidentified, genetic loci contributing to diabetes susceptibility in this strain. BB rats carrying wild-type Lyp alleles are not lymphopenic and are resistant to spontaneous diabetes (DR). Here we show that thymectomy and exposure to one sublethal dose of gamma-irradiation (TX-R) at 4 weeks of age result in the rapid development of insulitis followed by diabetes in 100% of DR rats. Administration of CD4(+)45RC(-) T-cells from unmanipulated, syngeneic donors immediately after irradiation prevents the disease. Splenic T-cells from TX-R-induced diabetic animals adoptively transfer type 1 diabetes to T-deficient recipients. ACI, WF, WAG, BN, LEW, PVG, and PVG.RT1(u) strains are resistant to TX-R-induced insulitis/diabetes. Genetic analyses revealed linkage between regions on chromosomes 1, 3, 4, 6, 9, and 16, and TX-R-induced type 1 diabetes in a cohort of nonlymphopenic F(2) (Wistar Furth x BBDP) animals. This novel model of TX-R-induced diabetes in nonlymphopenic BB rats can be used to identify environmental and cellular factors that are responsible for the initiation of antipancreatic autoimmunity.

T Cell Reconstitution of BB/W Rats After the Initiation of Insulitis Precipitates the Onset of Diabetes

One of the diabetes susceptibility genes of the BB/W (Biobreeding/Worcester) rat maps to the lyp locus on chromosome 4. The BB/W lyp allele is responsible for a severe peripheral T lymphopenia. Correction of this lymphopenia by transfer of normal, histocompatible T cells prevents diabetes, providing T cell reconstitution is initiated before insulitis. We have analyzed this time-dependent regulation of the diabetogenic process by normal T cells. We demonstrate that T cell reconstitution after the initiation of insulitis precipitates the onset of diabetes through the recruitment of donor T cells to the autoimmune process. This inability of normal T cells to regulate primed diabetogenic BB/W T cells and their own autoreactive potential were observed when normal T cells outnumbered pathogenic T cells by approximately 1000-fold. Analysis of donor-derived T cells recovered from BB/W rats that were reconstituted before insulitis, and hence protected from diabetes, demonstrates that early T cell reconstitution of BB/W rats does not result in a long term physical or functional depletion of islet cell-specific T cell precursors among donor cells or in the expansion of T cells that can regulate the activation and expansion of diabetogenic T cells.