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Query: UMLS:C0011854 (type 1 diabetes)
 20,749 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This paper introduces a model which incorporates fetal thymus organ culture (FTOC) from NOD mice to replicate thymic development of diabetogenic T cells. NOD fetal pancreas organ culture (FPOC) co-cultured with 13-16 day NOD FTOC for an additional 14-21 days produced less insulin than FPOC cultured alone. Insulin production from the FTOC of non-diabetic strains C57BL/6 and BALB/c was not inhibited by co-culture with FTOC from their syngeneic counterparts. Sections of the NOD co-cultures showed peri-islet infiltration with lymphocytes. Insulin reduction by FTOC/FP co-culture was prevented by co-culture of the NOD FT with FT from immunologically incompetent C.B-17 SCID/SCID mice. Co-culture of NOD FP with NOD FT prior to the development of T cells prevented generation of diabetogenic FTOC. Thus, early exposure of NOD T cell precursors to the thymic stromal elements of C.B-17 SCID/SCID FT or to islet antigens can negatively select for diabetogenic T cells or activate immuno-regulatory cells that can suppress diabetogenic T cell activity. The addition of blocking F(ab')2 fragments of anti-CD3epsilon monoclonal antibody to NOD FTOC/FP co-cultures prevented insulin reduction, implicating a role for TcR-mediated recognition in this "in vitro IDDM" model. The addition of activating whole anti-CD3epsilon caused the complete ablation of insulin production in FTOC/FP co-cultures from all strains tested. Transfer of unprimed syngeneic FTOC cells to prediabetic NOD mice prevented the onset of IDDM while transfer of islet-cell primed FTOC/FP cells slightly increased disease incidence. These data suggest that while diabetogenic T cells are present in the FT, they are normally suppressed, even after organ culture. However, these cells can induce the destruction of islet cells, in vitro and in vivo, if they are appropriately activated with pancreatic tissue.
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PMID:NOD fetal thymus organ culture: an in vitro model for the development of T cells involved in IDDM. 937 74

T cells from NOD mice display an age-dependent, TCR-inducible proliferative hyporesponsiveness that may be causal to IDDM. Exogenous IL-4 completely restores this hyporesponsiveness in vitro and prevents IDDM in vivo when administered to NOD mice. We therefore tested the hypothesis that stimulation of a Th2 response by either IL-4 or CD28 costimulation may block progression to IDDM. Low-dose IL-4 treatment beginning at 2 weeks of age (pre-insulitis) protects NOD mice from insulitis, sialitis, and thyroiditis, indicating that IL-4 modulates T cell migration to these inflammatory sites. Cytokine secretion profiles of stimulated T cells and assays of intrapancreatic cytokine concentrations revealed that IL-4 treatment prevents IDDM by stabilizing a protective Th2-mediated environment in the thymus, spleen, and pancreatic islets. Whereas treatment of NOD mice with an anti-CD28 mAb between 2 to 4 weeks of age inhibits destructive insulitis and protects against IDDM by enhancing IL-4 production by T cells, anti-CD28 treatment between 5 to 7 weeks of age does not prevent IDDM. Simultaneous anti-IL-4 treatment abrogates the protective effect conferred by anti-CD28 treatment. Our data demonstrate that stimulation of a Th2-cell-enriched environment in the pancreas during the inductive phase of disease development blocks progression to IDDM in NOD mice.
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PMID:Cytokine- and costimulation-mediated therapy of IDDM. 941 41

Genetic studies have identified a number of loci demonstrating linkage to type 1 diabetes. One of the largest single contributors to genetic susceptibility, after the major histocompatability complex, is the IDDM2 locus, which maps to a nontranscribed variable number of tandem repeats (VNTR) minisatellite upstream of the insulin (INS) and insulin-like growth factor 2 (IGF2) genes. In a progression from population to functional studies, recent reports have shown that VNTR susceptibility alleles (class I) have different transcriptional effects on INS than protective VNTR alleles (class III) in thymus and pancreas, two tissues important in the pathogenesis of the disease. Similar VNTR transcriptional effects on IGF2 have also been proposed as a mechanism by which the IDDM2 locus confers susceptibility in addition to, or instead of, effects on INS. We evaluated this hypothesis by comparing IGF2 expression levels from chromosomes with the protective class III alleles to those with class I alleles in tissues relevant to type 1 diabetes pathogenesis. In thymus, class III alleles were associated with an IGF2 mRNA level of 4.7 +/- 0.9 (mean +/- SE, arbitrary units, n = 12) compared with 4.7 +/- 1.3 for class I alleles (n = 17). The same absence of a significant difference was found in pancreas, where class III alleles were associated with a level of 28.4 +/- 4.2 (n = 7) and class I alleles with a level of 29.5 +/- 5.2 (n = 6). There was a significant correlation between fetal age and IGF2 in both tissues, but fetal ages were not different in the genotype groups compared. We therefore did not detect any significant difference in IGF2 mRNA levels associated with the protective class of VNTR alleles as compared with the predisposing class. This is evidence against the hypotheses that have suggested IGF2 is a mediator of IDDM2-encoded susceptibility and corroborates previous studies suggesting insulin is the gene involved.
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PMID:A functional analysis of the role of IGF2 in IDDM2-encoded susceptibility to type 1 diabetes. 958 57

IDDM results from the destruction of pancreatic beta-cells by autoreactive T-cells that appear to avoid deletion early in development, possibly due to improper interaction with antigen-presenting cells (APCs) resident in the thymus or periphery. In the nonobese diabetic (NOD) mouse, there exists a defect in APC function characterized by its failure to fully mature upon stimulation. The NOD mouse thus provides an excellent model for the investigation of APC dysfunction and development and how these relate to the incidence of autoimmune diabetes. We initiated studies of APC function in the NOD mouse with respect to antigen processing and presentation, using a well-characterized antigen hen egg lysozyme (HEL) and comparing it with the closely related, major histocompatibility complex (MHC) (I-Ag7) identical, diabetes-resistant mouse strain NOR. Proliferation assays comparing NOD and NOR HEL-specific T-cells demonstrated that the T-cell proliferation response of the NOD mouse to both native and denatured forms of the antigen is lower than that of NOR. When crisscross proliferation experiments were conducted using purified T-cells and irradiated spleen cells as APCs from both strains, the results demonstrated that the defect in proliferation resided in the APC compartment of activation. The levels of intracellular glutathione (GSH) were compared in splenic macrophages from NOD and NOR mice; it was found that on antigenic stimulation, NOR macrophages produced significantly more intracellular GSH than did NOD macrophages, even under hyperglycemic (50 mmol/l glucose) conditions. The lower amount of GSH seen in the NOD may result in less efficient processing of antigen, and subsequently, lower levels of T-cell activation.
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PMID:Splenic macrophages from the NOD mouse are defective in the ability to present antigen. 970 19

The IDDM2 susceptibility locus in type 1 diabetes corresponds to a variable number of tandem repeats (VNTR) upstream of the insulin (INS) and insulin-like growth factor 2 (IGF2) genes. Large VNTR alleles (class III) are dominantly protective, whereas small alleles (class I) are predisposing. IGF2 has been considered a prime candidate for mediating IDDM2-encoded susceptibility because of its proximity to the VNTR, mitogenic properties and parental effects at IDDM2 suggest the involvement of an imprinted gene. IGF2 is imprinted with exclusive expression of the paternal gene. However, there is polymorphic relaxation of IGF2 imprinting in leukocytes. VNTR allelic variation affecting either the extent of relaxation or transcription independent of parental origin might explain the IDDM2 effect. To test this, we compared IGF2 expression between chromosomes with a class III or I allele in leukocytes and stimulated lymphocytes. No significant difference was detected between the two classes. Furthermore, the (+) allele of an ApaI polymorphism in the 3'-untranslated region of IGF2 was associated with significantly higher IGF2 messenger ribonucleic acid levels than the (-) allele, but was not associated with type 1 diabetes. The absence of transcriptional effects in leukocytes on IGF2 by the VNTR, which is the disease-predisposing locus, and the presence of a strong association between IGF2 levels and ApaI, which is not associated with the disease, argue against IGF2 expression in leukocytes as the mediator of IDDM2-encoded susceptibility. Taken together, these results support studies suggesting that INS expression in the thymus is a primary target of the IDDM2 susceptibility locus.
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PMID:Divergence between genetic determinants of IGF2 transcription levels in leukocytes and of IDDM2-encoded susceptibility to type 1 diabetes. 970 72

MHC class II molecules function by selective binding of antigenic peptides, thereby both shaping the T-cell receptor (TCR) repertoire in the thymus and influencing presentation of immunogenic peptides to CD4+ T cells in the periphery. The strong association between a number of human autoimmune diseases (type 1 diabetes, rheumatoid arthritis, and multiple sclerosis) and certain HLA-DR/DQ alleles suggests that it may be possible to alter pathological autoimmune responses by deliberate introduction of autoantigenic peptides in a "tolerogenic" manner. Since there are likely to be differences in epitope selection and epitope spreading in different patients over time, this approach requires identification of all the immunogenic CD4+ T-cell epitopes (dominant, subdominant, or cryptic) of an autoantigen which elicit T-cell responses restricted to the HLA-DR/DQ alleles predisposing to these autoimmune diseases. This paper describes a new approach for the identification of immunogenic peptide epitopes of human autoantigenic proteins using HLA-DR and DQ transgenic mice. These mice are engineered to select a full TCR repertoire which can identify immunogenic peptide epitopes similar or identical to human subjects of the same HLA-DR/DQ genotype. This experimental system also allows comparison of autoantigenic immune responses restricted to disease-susceptible and disease-resistant HLA-DR/DQ alleles.
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PMID:Identification of autoantigen epitopes in MHC class II transgenic mice. 979 71

Type 1 diabetes is associated with autoimmunity to insulin. Genetic susceptibility to type 1 diabetes is polygenic and includes the INS VNTR-IDDM2 locus which may regulate the expression of insulin in pancreas and thymus. In order to determine whether insulin autoimmunity could be attributed to a genetic susceptibility conferred by the INS VNTR-IDDM2 locus, peripheral blood T cell proliferation to human insulin and insulin autoantibodies (IAA) was measured in patients with new onset type 1 diabetes and control subjects. IAA were detected in 21 of 53 patients and in none of 25 control subjects, while T cell responses were low (stimulation index range 0.4-7.2) and similar in both groups. Both antibody and T cell responses were higher in younger subjects and IAA were more prevalent in patients with the HLA-DR4 allele. No relationship was observed between humoral and cellular responses to insulin. No association was found between the INS VNTR-IDDM2-susceptible allele and insulin autoimmunity. Increased T cell responses and IAA were found in patients with either the diabetes-susceptible or the diabetes-protective INS VNTR-IDDM2 locus genotypes, and increased T cell responses were also found in control subjects with either susceptible or protective INS VNTR-IDDM2 locus genotypes. This study confirms that primary T cell proliferative responses to insulin are low and detectable also in control subjects. The detection of T cell proliferation and autoantibodies to insulin in subjects with and without the protective INS VNTR-IDDM2 locus genotypes does not support the hypothesis of an allele-specific capacity for tolerance induction which could determine a susceptibility to develop autoimmunity against the insulin protein and subsequently diabetes.
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PMID:Autoimmune responses to the beta cell autoantigen, insulin, and the INS VNTR-IDDM2 locus. 984 45

Thymic epithelium, including nurse cells (TEC/TNC), as well as other thymic stromal cells (macrophages and dentritic cells), express a repertoire of polypeptide belonging to various neuroendocrine protein families (such as the neurophypophysial, tachykinin, neurotensin and insulin families). A hierarchy of dominance exists in the organization of the thymic repertoire of neuroendocrine precursors. Oxytocin (OT) is more expressed in the TEC/TNC than vasopressin (VP); insulin-like growth factor 2 (IGF-2) thymic expression predominates over IGF-1, and much more over (pro)insulin. Thus, OT was proposed to be the self antigen of the neurohypophysial family, and IGF-2 the self antigen precursor of the insulin family. The dual role of the thymus in T-cell life and death is recapitulated at the level of the thymic neuroendocrine protein repertoire. Indeed, thymic polypeptides behave as accessory signals involved in T-cell development and positive selection according to the cryptocrine model of signaling. Moreover, thymic neuroendocrine polypeptides are the source of self antigens presented by thymic MHC molecules to developing pre-T cells. This presentation might induce the negative selection of T cells bearing a randomly rearranged antigen receptor (TCR) oriented against neuroendocrine families. Using an animal model of autoimmune type 1 diabetes (BB rat), we have shown a defect in intrathymic expression of the self antigen of the insulin family (IGF-2) and in IGF-2-mediated T-cell education to recognize and tolerate the insulin family. Altogether these studies have enlightened the crucial role played by the thymus in the induction of the central self tolerance of neuroendocrine families. The tolerogenic properties of thymic self peptides could be used in a novel type of vaccination for the prevention of autoimmune diseases.
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PMID:The thymic repertoire of neuroendocrine-related self antigens: biological role in T-cell selection and pharmacological implications. 987 42

Continuing progress has been made in elucidating the genetic factors involved in type 1 diabetes (insulin-dependent diabetes mellitus [IDDM]) in the past year. Two genome scans suggested additional susceptibility intervals and provided supporting evidence for several previously reported linkages. Other studies focused on the confirmation of linkage using multipoint sibpair analyses with densely spaced markers and multiethnic collections of families. Although significant and consistent linkage evidence was reported for the susceptibility intervals IDDM8 (on human chromosome 6q27), IDDM4 (on 11q) and IDDM5 (on 6q25), evidence for most other intervals varies in different data sets -probably due to a weak effect of the disease genes, genetic heterogeneity or random variation. Linkage disequilibrium mapping has become an increasingly important tool for both the confirmation and fine-mapping of susceptibility intervals, as well as identification of etiological mutations. Functional studies indicate, firstly, that the susceptible and protective HLA class II molecules HLA-DR and -DQ bind and present nonoverlapping peptides and, secondly, that the variable number of tandem repeats at the 5' end of the insulin gene (susceptibility interval IDDM2) regulates insulin expression in the thymus.
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PMID:Genetic susceptibility factors in type 1 diabetes: linkage, disequilibrium and functional analyses. 991 16

MHC class I and II molecules play a central role in the immune response against a variety of invading microorganisms and cells that have undergone malignant transformation by shaping the T cell repertoire in the thymus and by presenting peptide antigens from endogenous and exogenous antigens in the periphery to CD8+ cytotoxic T cells and CD4+ helper T cells. In certain situations MHC-peptide complexes may, however, also initiate and perpetuate an autoimmune attack mediated by autoaggressive T cells leading to diseases such as insulin dependent diabetes mellitus (IDDM), rheumatoid arthritis (RA) and multiple sclerosis (MS). Such MHC-peptide complexes are a desirable target for novel approaches in immunotherapy. Targeted delivery of toxins or other cytotoxic drugs to cells which express specific MHC-peptide complexes that are involved in the immune response against cancer or viral infections and specific masking of MHC-peptide complexes that are involved in autoimmune reactions would allow for a specific immunotherapeutic treatment of these diseases. We have recently demonstrated that antibodies with the antigen-specific, MHC restricted specificity of T cells can be readily generated by taking advantage of the selection power of phage display technology.
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PMID:Recombinant antibodies with the antigen-specific, MHC restricted specificity of T cells: novel reagents for basic and clinical investigations and immunotherapy. 1023 Oct 96


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