Transplantation analysis of B cell destruction in (NOD x CBA)F1 mouse bone marrow chimeras

The Type 1 Diabetes-Resistance Locus Idd22 Controls Trafficking of Autoreactive CTLs into the Pancreatic Islets of NOD Mice

Type 1 diabetes (T1D) has a strong genetic component. The insulin dependent diabetes (Idd)22 locus was identified in crosses of T1D-susceptible NOD mice with the strongly T1D-resistant ALR strain. The NODcALR-(D8Mit293-D8Mit137)/Mx (NOD-Idd22) recombinant congenic mouse strain was generated in which NOD mice carry the full Idd22 confidence interval. NOD-Idd22 mice exhibit almost complete protection from spontaneous T1D and a significant reduction in insulitis. Our goal was to unravel the mode of Idd22-based protection using in vivo and in vitro models. We determined that Idd22 did not impact immune cell diabetogenicity or β cell resistance to cytotoxicity in vitro. However, NOD-Idd22 mice were highly protected against adoptive transfer of T1D. Transferred CTLs trafficked to the pancreatic lymph node and proliferated to the same extent in NOD and NOD-Idd22 mice, yet the accumulation of pathogenic CTLs in the islets was significantly reduced in NOD-Idd22 mice, correlating with disease resistance. Pancreatic endothelial cells from NOD-Idd22 animals expressed lower levels of adhesion molecules, even in response to inflammatory stimuli. Lower adhesion molecule expression resulted in weaker adherence of T cells to NOD-Idd22 endothelium compared with NOD-derived endothelium. Taken together, these results provide evidence that Idd22 regulates the ability of β cell-autoreactive T cells to traffic into the pancreatic islets and may represent a new target for pharmaceutical intervention to potentially prevent T1D.

Cell Surface Modification by Activated Polyethylene Glycol Prevents Allosensitization after Islet Transplantation

The necessity to transplant islet tissue without the need for immunosuppressant therapy has led to the development of materials for immune modulation. Pegylation makes islets antigenically silent, protecting them from the adsorption of foreign protein and thus avoiding immune injury. The aim of this study is to determine whether pegylation of islets prolongs islet survival and function both during tissue culture and posttransplantation. We used cyanuric chloride-activated methoxy-polyethylene glycol for cell surface modification. To detect the pegylation effect on splenocytes, we measured antibody binding inhibition and abrogation of lymphocyte proliferation. To detect the pegylation effect on islet grafts, we performed rodent islet transplantation. Islet viability and function were maintained after pegylation. Pegylated islets showed a 90% decrease in antibody binding and decreased lymphocyte proliferation in a mixed lymphocyte culture. However, when pegylated islets were transplanted, no prolongation of graft survival was observed. When a subtherapeutic dose of immunosuppressant was given at the time of transplantation of pegylated islets, islet graft survival was significantly prolonged. In addition, when rats were sensitized with donor splenocytes, graft survival was prolonged by pegylation. We observed that pegylation of islets, combined with a subtherapeutic dose of immunosuppressant, protects the graft from rejection. Prolonged graft survival in sensitized recipients showed that pegylation of islets shifted the pattern of rejection from an acute humoral response to a less aggressive cellular alloresponse.

Mechanisms underlying resistance of pancreatic islets from ALR/Lt mice to cytokine-induced destruction

Nuclear and mitochondrial genomes combine in ALR/Lt mice to produce systemically elevated defenses against free radical damage, rendering these mice resistant to immune-mediated pancreatic islet destruction. We analyzed the mechanism whereby isolated islets from ALR mice resisted proinflammatory stress mediated by combined cytokines (IL-1beta, TNF-alpha, and IFN-gamma) in vitro. Such damage entails both superoxide and NO radical generation, as well as peroxynitrite, resulting from their combination. In contrast to islets from other mouse strains, ALR islets expressed constitutively higher glutathione reductase, glutathione peroxidase, and higher ratios of reduced to oxidized glutathione. Following incubation with combined cytokines, islets from control strains produced significantly higher levels of hydrogen peroxide and NO than islets from ALR mice. Nitrotyrosine was generated in NOD and C3H/HeJ islets but not by ALR islets. Western blot analysis showed that combined cytokines up-regulated the NF-kappaB inducible NO synthase in NOD-Rag and C3H/HeJ islets but not in ALR islets. This inability of cytokine-treated ALR islets to up-regulate inducible NO synthase and produce NO correlated both with reduced kinetics of IkappaB degradation and with markedly suppressed NF-kappaB p65 nuclear translocation. Hence, ALR/Lt islets resist cytokine-induced diabetogenic stress through enhanced dissipation and/or suppressed formation of reactive oxygen and nitrogen species, impaired IkappaB degradation, and blunted NF-kappaB activation. Nitrotyrosylation of beta cell proteins may generate neoantigens; therefore, resistance of ALR islets to nitrotyrosine formation may, in part, explain why ALR mice are resistant to type 1 diabetes when reconstituted with a NOD immune system.

Fine-mapping of the mouse T lymphocyte fraction (Tlf) locus on chromosome 9: association with autoimmune diabetes

Tlf (T lymphocyte fraction) defines a locus that governs the unusually high fraction of circulating T lymphocytes in the nonobese diabetic (NOD) mouse. We previously mapped Tlf to proximal Chromosome 9 in BC1 mice. Here, Tlf was tine-mapped on Chromosome 9 using 8 markers covering the 43 cM interval from D9Mit90 at 9 cM to D9Mit35 at 52 cM. Markers for diabetic genes on Chromosomes 3, 4, 5, 6, and 17 were also examined for effects on the Tlf phenotype. By both parametric and nonparametric tests. Tlf associated with two areas on Chromosome 9, one with the segment bounded by D9Mit66 (15 cM) and D9Mit2 (17 cM) and a second region near D9Mit71 (29 cM). This linkage pattern was observed both in BC1 and F2 populations. Thus, the Tlf phenotype is possibly governed by two genes on Chromosome 9. An influence by sex on the penetrance of Tlf was evident in that linkage was strongest for female F2 mice and male BC1 mice. One locus controlling the T lymphocyte fraction may be Idd2 since historically a subline of NOD mice with a low T cell fraction showed a low incidence of diabetes. Candidate genes for Tlf are Ets1 and Fli1, proximally and Igif distally.

Subcongenic Analysis of the Idd13 Locus in NOD/Lt Mice: Evidence for Several Susceptibility Genes Including a Possible Diabetogenic Role for β2-Microglobulin

Although they share ∼88% of their genome with NOD mice including the H2g7 haplotype, NOR mice remain free of T cell-mediated autoimmune diabetes (IDDM), due to non-MHC genes of C57BLKS/J (BKS) origin. NOR IDDM resistance was previously found to be largely controlled by the Idd13 locus within an ∼24 cM segment on Chromosome 2 encompassing BKS-derived alleles for H3a, B2m, Il1, and Pcna. NOD stocks carrying subcongenic intervals of NOR Chromosome 2 were utilized to more finely map and determine possible functions of Idd13. NOR- derived H3a-Il1 (∼6.0 cM) and Il1-Pcna (∼1.2 cM) intervals both contribute components of IDDM resistance. Hence, the Idd13 locus is more complex than originally thought, since it consists of at least two genes. B2m variants within the H3a-Il1 interval may represent one of these. Monoclonal Ab binding demonstrated that dimerizing with the β2ma (NOD type) vs β2mb isoform (NOR type) alters the structural conformation, but not total expression levels of H2g7 class I molecules (e.g. Kd, Db). β2m-induced alterations in H2g7 class I conformation may partially explain findings from bone marrow chimera analyses that Idd13 modulates IDDM development at the level of non-hematopoietically derived cell types controlling selection of diabetogenic T cells and/or pancreatic β cells targeted by these effectors. Since trans-interactions between relatively common and functionally normal allelic variants may contribute to IDDM in NOD mice, the search for Idd genes in humans should not be limited to functionally defective variants.

Abnormal T cell selection on nod thymic epithelium is sufficient to induce autoimmune manifestations in C57BL/6 athymic nude mice

To investigate the role of primary T cell repertoire selection in the immunopathogenesis of autoimmune diseases, pure thymic epithelium (TE) from nonobese diabetic (NOD) embryos was grafted into non autoimmune prone newborn C57BL/6 athymic mice. The results show that NOD TE selects host T cell repertoires that establish autoimmunity in otherwise nondiabetic animals. Thus, such chimeras regularly show CD4 and CD8 T cell-mediated insulitis and sialitis, in contrast with syngeneic or allogeneic chimeras produced with TE from nonautoimmune strains. This is the first demonstration that autoimmunity to pancreatic beta cells and salivary glands can be established by the sole alteration of the thymic environment involved in T cell selection, regardless of the nature and presentation of both major histocompatibility complex and tissue-specific antigens on the target organ. These data indicate that T cell repertoire selection by the NOD thymic epithelium is sufficient to induce specific autoimmune characteristics in the context of an otherwise normal host.

Lack of preservation of higher brain function during hypoglycaemia in patients with intensively-treated IDDM

Severe hypoglycaemia with cognitive dysfunction is 3 times more common in intensively, rather than conventionally, treated insulin-dependent diabetes mellitus (IDDM). To investigate the effect of diabetes control on higher brain function during acute hypoglycaemia, we studied one of the earliest detectable changes in cognitive function, i.e. the four-choice reaction time, and symptomatic and hormonal responses during euglycaemic and hypoglycaemic clamping in human subjects. There were no changes in symptoms or counterregulatory hormones and four-choice reaction time was stable during 220 min of euglycaemic insulin clamping in five men with IDDM, with a coefficient of variation of less than 2.2% (1% for accuracy) for the cognitive function test. During stepped hypoglycaemic clamping however, hormonal responses and subjective awareness of hypoglycaemia occurred in all groups but started at much lower blood glucose concentrations in eight intensively-treated diabetic subjects (Group 1) than in ten conventionally-treated (Group 2) or in eight non-diabetic subjects (Group 3). For example, for adrenaline, plasma glucose thresholds were 2.7 +/- 0.2 vs 3.4 +/- 0.2 and 3.2 +/- 0.1 mmol/l, respectively, p < 0.05, Group 1 vs Groups 2 or 3 and for subjective awareness of hypoglycaemia 2.3 +/- 0.2 vs 3.0 +/- 0.1 and 3.2 +/- 0.1 mmol/l, p < or = 0.003), as in previous studies. In contrast, deterioration in reaction time occurred at 3.2 +/- 0.3, 3.2 +/- 0.2 and 3.0 +/- 0.2 mmol/l, respectively (p = NS), thus occurring at higher glucose levels than subjective awareness in the intensively-treated subjects only. The altered hierarchy of responses to hypoglycaemia in well-controlled intensively-treated diabetes explains the increased risk of severe hypoglycaemia without warning seen in such patients.

Autoimmune polyendocrine failure--type 1 (insulin-dependent) diabetes mellitus and hypothyroidism--after allogeneic bone marrow transplantation in a patient with lymphoblastic leukaemia

In this report we describe a patient who, after allogeneic bone marrow transplantation from her HLA-identical sister, developed polyendocrine failure in the form of Type 1 (insulin-dependent) diabetes mellitus and hypothyroidism. This was the result of the transfer of donor lymphoid cells which were activated by allogeneic bone marrow transplantation. The full chimerism of the recipient was demonstrated by restriction fragment length polymorphism analysis from nucleated blood cells and fibroblast DNA. During the 9-year follow-up, the donor developed hypothyroidism and signs of pre-Type 1 diabetes. This clinical observation resembles the adoptive transfer of diabetes observed in non-obese-diabetic mice and BB rats and confirms the role of immune processes in the pathogenesis of this disease.

Transfer of insulin-dependent diabetes between HLA-identical siblings by bone marrow transplantation

Insulin-dependent diabetes was observed in a woman, aged 29, 4 years after transplantation of bone marrow from her HLA-identical brother with insulin-dependent diabetes. Both had classic symptoms and insulin dependency from onset. At diagnosis of diabetes the recipient was positive for high-titre islet cell antibodies (ICA) whereas she had been ICA negative before transplantation. Chromosomal analyses verified that all circulating leucocytes were of male donor type. These findings suggest transfer of insulin-dependent diabetes by bone marrow cells and confirm the immune nature of the disease.

Diabetes intervention therapy

The involvement of autoreactive T cells in autoimmune diseases suggests the potential for intervention therapy in the setting of insulin-dependent diabetes mellitus. In the nonobese diabetic mouse, diabetes and insulitis have been inhibited by the modification of an amino acid in the major histocompatibility complex and by administration of anti-I-A antibody. T-cell vaccination has been shown to prevent autoimmune disease in animal models, and research is ongoing to develop monoclonal antibodies to a variety of T-cell receptor components. Strategies assessed in the clinical context include the administration of azathioprine, cyclosporine, and the antioxidant nicotinamide. Other potential strategies include the induction of specific oral tolerance, insulin prophylaxis, immunoenhancement therapy, and dietary manipulation.

Beta cell expression of endogenous xenotropic retrovirus distinguishes diabetes-susceptible NOD/Lt from resistant NON/Lt mice

Endogeneous retroviral expression in beta cells is a feature of prediabetes in nonobese diabetic (NOD) mice. The purpose of this study was to characterize the class-specific pattern of retroviral gene expression in NOD/Lt beta cells versus a related, but diabetes-resistant strain, NON/Lt. Electron microscopic comparison of beta cells from both strains indicated low constitutive expression of the intracisternal type A (IAP) retroviral class. However, NOD beta cells, in contrast to NON beta cells, expressed an additional intracisternal retroviral form resembling a type C particle. Antibodies against both IAP and type C were detected in NOD, with the humoral response to type C, but not IAP, preceding decline in beta cell function. RNA was extracted from freshly isolated islets from NOD and NON males. Comparative Northern blot analysis of total type C retroviral gene expression using a gag-pol DNA probe corroborated expression of endogenous type C proviruses in both NOD and NON islet cells and thymus. Use of class-specific retroviral probes identified the class of expressed endogenous retrovirus distinguishing the two inbred strains. The single ecotropic provirus present in both the NOD and NON genome (Emv-30) was not expressed in islets or thymus of either strain. Comparison of endogenous xenotropic provirus content by Southern blot analysis revealed two unique xenotropic loci (Xmv-65, -66) in NOD; 8.4 and 3.0 kb xenotropic envelope (env) RNA transcripts were detected in NOD, but not NON islets and thymus. NON contained three xenotropic loci common to other inbred strains (Xmv-21, -25, and -28). Both strains were partially characterized for content of recombinant (polytropic and modified polytropic) proviruses. IAP RNA expression was common to both NOD and NON islets and hence could not be specifically associated with the unique intracisternal type C particle found in NOD, but not NON beta cells. In conclusion, this study shows that expression of xenotropic type C but not IAP distinguishes retroviral activity in NOD/Lt versus NON/Lt beta cells. The potential pathogenic role of retroviral gene expression in NOD beta cells is discussed.

Intervention therapies for insulin-dependent diabetes

Treatment of insulin-dependent diabetes remains problematic since there continues to be high rates of morbidity and mortality among affected patients. Good outcomes are most likely to be more common among patients who maintain endogenous insulin reserves for the longest time following diagnosis. The disease process can now be identified in its early, pre-symptomatic stages and thus, the time has come for the investigation of preventive therapies through multicenter clinical trials. A wide variety of strategies are available and their choice should be dependent on the pathogenic stage of disease at which treatment is initiated. This stage-specific approach to prevention is discussed with a particular focus on those therapies that will soon be tested in clinical trials.