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N Sarvetnick

Publications and source records attributed to N Sarvetnick.

At least 109 records · Page 6Linked to original sources
PubMed1994

Production of interleukin 10 by islet cells accelerates immune-mediated destruction of beta cells in nonobese diabetic mice.

The T helper type 2 (Th2) cell product interleukin 10 (IL-10) inhibits the proliferation and function of Th1 lymphocytes and macrophages (M phi). The nonobese diabetic mouse strain (NOD/Shi) develops a M phi and T cell-dependent autoimmune diabetes that closely resembles human insulin-dependent diabetes mellitus (IDDM). The objective of the present study was to explore the consequences of localized production of IL-10 on diabetes development in NOD/Shi mice. Surprisingly, local production of IL-10 accelerated the onset and increased the prevalence of diabetes, since diabetes developed at 5-10 wk of age in 92% of IL-10 positive I-A beta g7/g7, I-E- mice in first (N2) and second (N3) generation backcrosses between IL-10 transgenic BALB/c mice and (NOD/Shi) mice. None of the IL-10 negative major histocompatibility complex-identical littermates were diabetic at this age. Furthermore, diabetes developed in 33% of I-A beta g7/d, I-E+ N3 mice in the presence of IL-10 before the mice were 10 wk old. Our findings support the notion that IL-10 should not simply be regarded as an immunoinhibitory cytokine, since it possesses powerful, immunostimulatory properties as well. Furthermore, our observations suggest that beta cell destruction in NOD mice may be a Th2-mediated event.

Animals↗
PubMed1994

A transgenic model for studying islet development.

The regeneration of islet cells in a transgenic mouse strain harboring the interferon-gamma gene (IFN-gamma) linked to the insulin promoter DNA fragment (ins-IFN-gamma) is described. The regeneration follows the loss of islets by an immune response provoked by IFN-gamma and manifests in the proliferation of duct cells, the presence of progenitor cells, and the formation of buds and isletlike structure. All three types (A, B, and D) of four endocrine cells identified by immunolabeling are present. The progenitor cells express neuronal enzymes, tyrosine hydroxylase (TH) and glutamic acid decarboxylase (GAD), as revealed by specific antibodies. The results indicate that the islet regeneration closely resembles the embryonic islet differentiation and serves as a model for studying islet development. The expression of neuronal enzymes by islet progenitor cells signifies yet unknown relationships to the nervous tissue. GAD, recognized as an autoantigen in insulin-dependent diabetes mellitus (IDDM) and stiff-man syndrome, may provide a clue to the mechanism of autoimmune disease.

Animals↗
PubMed1994

Postnatal anti-interferon-gamma treatment prevents pancreatic inflammation in transgenic mice with beta-cell expression of interferon-gamma.

beta-Cell-targeted expression of interferon-gamma (IFN-gamma) leads to pancreatitis and immune sensitization to beta-cells. This transgenic model is used to explore the possible role of locally produced IFN-gamma in loss of tolerance to beta-cell-specific antigens in insulin-dependent diabetes mellitus (IDDM). The aim of the present study was to test if postnatal treatment with antibodies against IFN-gamma could inhibit morphological changes in the IFN-gamma transgenic pancreas, even though the transgene is expressed during embryogenesis. Treatment with a monoclonal rat anti-mouse IFN-gamma antibody for 6 weeks, starting from 5 to 7 days of age, completely inhibited IFN-gamma-induced morphological changes in the pancreas, and only a modest inflammatory reaction emerged after prolonged treatment for 12 weeks. The lack of morphological changes may reflect the ability of nonterminally differentiated neonatal pancreatic cells to compensate for transgene-induced pathological alterations occurring in utero prior to the antibody treatment. We conclude that inflammation and altered pancreas morphology in the transgenic mice is the result of the biological actions of IFN-gamma and not by disrupted islet development due to transgene overexpression in the pancreatic beta-cells. Furthermore, our treatment schedule can serve as a model for future intervention studies in the transgenic mice, elaborating the role of IFN-gamma in localized inflammatory reactions, IDDM in particular.

Animals↗
PubMed1994

Ectopic expression of gamma interferon in the eye protects transgenic mice from intraocular herpes simplex virus type 1 infections.

Transgenic (rho gamma) mice provide a model for studying the influence of gamma interferon (IFN-gamma) produced in the eye on ocular and cerebral viral infection. To establish this model, we injected BALB/c- and C57BL/6-derived transgenic and nontransgenic mice of different ages intravitreally with herpes simplex virus type 1 (HSV-1) strain F. Eye and brain tissues of these mice were assessed for pathological and immunocytochemical changes. HSV-1 infection induced severe retinitis of the injected eyes and infection of the brain in all mice. In transgenic mice inoculated with HSV-1, the left, nontreated eyes were protected from retinitis, whereas nontransgenic mice developed bilateral retinitis. Additional intravitreal injection of IFN-gamma with the virus protected the noninoculated eyes of nontransgenic mice. Three-week-old nontransgenic mice died from HSV-1 infection, whereas transgenic mice of the same age and nontransgenic mice intravitreally treated with IFN-gamma survived. Ocular IFN-gamma production increased the extent of inflammation in transgenic mice but did not have a significant influence on the growth of HSV-1 until day 3 after inoculation and did not influence the neuroinvasion of this virus. Thus, the effects of IFN-gamma were not caused by an early block of viral replication. Possible mechanisms of IFN-gamma action include activation of the immune response, alteration of the properties of the virus, and direct protection of neurons.

Animals↗
PubMed1994

Pancreatic islet production of murine interleukin-10 does not inhibit immune-mediated tissue destruction.

IL-10 inhibits macrophage-dependent antigen presentation, cytokine production, and generation of allospecific cells in vitro. These findings have lead to the widespread expectation that IL-10 may be a useful immunosuppressive agent to inhibit allograft rejection or autoimmunity in vivo. We used two experimental paradigms to study effects of murine IL-10 on in vivo immune responses. First, fetal pancreata or adult pancreatic islets from transgenic mice expressing IL-10 in pancreatic beta cells (Ins-IL-10 mice) were grafted across the MHC barrier to examine if IL-10 could inhibit allograft rejection. Second, Ins-IL-10 mice were crossed with transgenic mice expressing lymphocytic choriomeningitis virus (LCMV) antigens in pancreatic beta cells. These mice were infected with LCMV to elicit autoimmune diabetes, allowing us to ask if IL-10 protects islets from autoimmune destruction. We observed that allografts from IL-10-transgenic donors were rejected with comparable kinetics to the rejection of control nontransgenic allografts, indicating that IL-10 does not inhibit allograft rejection. After LCMV infection, IL-10 and LCMV antigen double transgenic mice developed diabetes earlier than LCMV antigen single transgenic littermates, suggesting that IL-10 does not inhibit islet antigen presentation or recognition. Our results contrast to in vitro observations and suggest that IL-10 cannot overcome immune-mediated tissue destruction within the pancreas.

Animals↗
PubMed1994

Transitional cells in the regenerating pancreas.

We examined the spectrum of intermediate cell types in the regenerating pancreas as duct epithelial cells progressed through their differentiation pathway to become mature endocrine cells. The model used was transgenic mice in which the pancreatic islets continue to grow during adulthood, unlike normal mice whose islet cell formation ceases early in life. Because the intermediate cells migrated into islet-like clusters at specific locations, we propose a specific pathway for islet development. Endocrine cells are derived from duct cells co-expressing a duct cell antigen, carbonic anhydrase II (CA II) and an exocrine enzyme, amylase. The CA II/amylase cells become amylase/endocrine intermediate cells as they exited from their lumenal location. The abluminal amylase/endocrine cells continue to differentiate to multihormone-bearing young endocrine cells, which migrated to form clusters with other differentiating endocrine cells.

Amylases↗
PubMed1994

Transgenic mice expressing IFN-gamma in the retina develop inflammation of the eye and photoreceptor loss.

PURPOSE: Inflammatory mediators such as interferon-gamma (IFN-gamma) are thought to play a role in ocular disease. Although IFN-gamma was found in the vitreous of mice with experimentally induced autoimmune uveitis, intracameral injection of this cytokine did not induce intraocular inflammation in mice. Therefore, the authors created a transgenic mouse line using the rhodopsin promoter to direct the expression of IFN-gamma in the photoreceptor cells of the retina. These mice, designated rho gamma, enabled them to model intraocular inflammatory disease. METHODS: The authors fused a 2.1 kb 5' Hind III fragment from the murine rhodopsin gene to the IFN-gamma gene and introduced the DNA construct into fertilized zygotes. These were implanted into pseudopregnant C57BL/6 mice, and the resulting progeny were crossed back to balb/c mice. The transgene was identified by Southern blot hybridization. Eyes from the rho gamma mice were either fixed in zinc formalin and stained with hematoxylin and eosin or were frozen in OCT compound and processed for immunostaining using the indirect immunoperoxidase method with DAB as a chromogen. RESULTS: The rho gamma transgenic mice developed intraocular disease, manifested as intraocular cellular infiltration, loss of photoreceptors, corneal clouding, cataract formation, and epithelial and microglial proliferation. Additionally, rho gamma mice exhibited antigenic changes, comprising GFAP expression on Müller cells, accumulation of neurofilament on photoreceptors, and expression of MHC class I and class II molecules on retinal cells. CONCLUSIONS: IFN-gamma alters the antigenic properties of intraocular tissue and induces intraocular inflammation in mice. The results suggest a key position of IFN-gamma in the development of pathologic conditions related to intraocular inflammation and provide a useful animal model for the further study of inflammatory disorders, including autoimmune diseases.

Animals↗
PubMed1993

Leukocyte extravasation into the pancreatic tissue in transgenic mice expressing interleukin 10 in the islets of Langerhans.

Transgenic expression of interleukin 10 (IL-10) in the islets of Langerhans leads to a pronounced pancreatic inflammation, without inflammation of the islets of Langerhans and without diabetes. A scattered infiltration of macrophages (M pi) precedes localized accumulations of CD4+ and CD8+ T lymphocytes, B lymphocytes, and M pi. This recruitment of inflammatory cells to the pancreas is somewhat surprising, since the biological activities of IL-10 in vitro indicate that IL-10 is a powerful immunosuppressive cytokine. Since endothelial cells play a major role in leukocyte extravasation, we examined if vascular changes and extralymphoid induction of peripheral and mucosal type vascular addressins contributed to IL-10-induced homing of mononuclear cells to the pancreas. The endothelium lining small vessels was highly activated in areas of inflammation, as the endothelial cells became cuboidal, and exhibited increased expression of major histocompatibility complex class II (Ia), intercellular adhesion molecule 1, and von Willebrand Factor. Furthermore, induction of vascular addressins simultaneously with accumulation of mononuclear cells around islets and vessels indicated that the endothelial cells take on the phenotype of differentiated endothelium specialized for leukocyte extravasation. In conclusion, pancreatic inflammation and vascular changes are prominent in IL-10 transgenic mice. We hypothesize that IL-10, in addition to its immuno-inhibitory properties, is a potent recruitment signal for leukocyte migration in vivo. These effects are relevant for in vivo therapeutic applications of IL-10.

Animals↗
PubMed1993

Increasing the chemical potential of the germ-line antibody repertoire.

To augment the chemical potential of the immunological repertoire, a metal ion-binding light chain has been introduced into the murine genome. Mice containing the transgene were subsequently immunized with a fluorescein conjugate. The transgenic light chain was found at a high frequency in the anti-fluorescein memory B-cell compartment. This general method should be applicable to other cofactors and small molecules and should lead to generation of antibodies with unique catalytic activities.

Animals↗
PubMed1993

Functional effects of transgenic expression of cholera toxin in pancreatic beta-cells.

Investigation of intracellular pathways of stimulus-secretion signaling in vivo is possible by transgenic expression of agents known to influence specific biochemical interactions in the cells. The objective of the present study was to establish an experimental model for analyzing signal transduction mechanisms in pancreatic beta-cells in vivo, by expressing the cholera toxin A1 subunit under control of the insulin promoter, intending a constant activation of the Gs-protein, and thereby constant generation of cAMP. Surprisingly, the transgenic mice demonstrated mild hyperglycemia and hypoinsulinemia in vivo, and diminished glucose-induced insulin release from the in vitro perfused pancreas, whereas the pancreatic insulin content was normal. These observations suggest a deficiency in either the insulin release mechanisms or glucose recognition. Although the translated cholera toxin A1 subunit was biologically active, there was no increase in the islet content of cAMP. We conclude that the observed phenotype in the cholera toxin transgenic mice may be caused by a deleterious effect of the transgene itself on beta-cell function, or that counter regulatory mechanisms may compensate for the transgene-induced changes in intracellular enzymatic pathways.

1-Methyl-3-isobutylxanthine↗
PubMed1993

Epithelial cell proliferation and islet neogenesis in IFN-g transgenic mice.

We have identified a model system for the study of pancreatic islet development and regeneration in transgenic mice bearing the interferon-gamma (IFN-g) gene expressed in the pancreatic islets. Previous studies showed that the locally produced IFN-g causes lymphocyte infiltration and islet cell destruction. Here we demonstrate that new islet cells are formed continuously from duct cells as evidenced by (1) the dramatic proliferation of duct cells, (2) the appearance of primitive cells and (3) their subsequent differentiation to endocrine cells. The IFN-g induced islet neogenesis is similar to embryonic islet morphogenesis and offers a model system for studying factors modulating islet development. Additionally, the duct cells occasionally transdifferentiate to gastrointestinal-like cell types and hepatocytes. These results underscore the lymphokine's ability to initiate a complex 'transdifferentiation' pathway, providing a window for understanding lineage interrelationships within a terminally differentiated structure.

Animals↗
PubMed1992

Genetic control of diabetes mellitus.

Genetic inheritance predisposing individuals to diabetes mellitus was discussed in this work group. The two forms of the disease, Type 1 (insulin-dependent) and Type 2 (non-insulin-dependent) were discussed separately since the pattern of inheritance and genes involved appear to be distinctly different. Within these subtypes there is considerable genetic heterogeneity, and superimposed environmental factors confound the analysis. New technologies that will allow finer molecular analysis, as well as new candidates genes, were presented.

Animals↗
PubMed1992

Transgenes in autoimmunity.

The ability of transgenic mice to express a specific protein in a specific tissue has enabled the mechanisms of self-tolerance and autoimmunity to be elucidated. Further studies, combined with more sophisticated methods of gene targeting, will provide insights into the pathway leading from loss of self-tolerance to autoimmunity.

Animals↗
PubMed1992

Effect on insulin production sorting and secretion by major histocompatibility complex class II gene expression in the pancreatic beta-cell of transgenic mice.

Expression of major histocompatibility complex (MHC) class II protein in islet beta-cells of transgenic mice causes severe diabetes without an attendant autoimmune component. Little is known of the aberrant beta-cell function and site of biological lesions responsible for the diabetic state. Therefore, changes in (pro)insulin production, processing, sorting, storage, and secretion were evaluated using the in vitro perfused pancreas from male hyperglycemic BALB/cBYJ Tg (O pinsproA alpha d pinsproA beta d) mice and a RIA capable of detecting mouse insulin or proinsulin with quantitative equivalency. Results were compared to control pancreases from normal BALB/cBYJ mice. Extractable pancreatic insulin plus proinsulin content in the transgenics was 4% of normal. Normal pancreases responded characteristically with a diphasic insulin release during 30-min stimulation by glucose, a response that was enhanced by subsequent forskolin. In contrast, hormone release from transgenic pancreases was undetectable; based on the sensitivity of the immunoassay, fractional secretion of the residual pancreatic hormone content from the transgenic pancreases was less than 25% of normal. Proinsulin or insulin constitutive release was also not detected in the absence or presence of glucose-containing stimuli even when experiments were extended to 3 h. In contrast, fractional secretion in response to nonglucose stimuli (carbachol-leucine and arginine-leucine) was greater than normal from the transgenic diabetic pancreases. Responses to glucose stimuli did not normalize even after 90 min in the absence of glucose. In other experiments, pancreases were stimulated with carbachol/leucine/forskolin for 90 min, and the proportion of proinsulin to insulin released by the regulated pathway was determined after Sep-Pak and HPLC separation of combined eluates. Proinsulin was undetectable (and, therefore, accounted for less than 10% of the total hormone secretion). It is concluded from the observations of hyperglycemia, low pancreatic insulin content, and impaired release that insulin production in the pancreas of the MHC diabetic transgenic is severely depressed. The limited insulin production and chronic hyperglycemia do not (as speculated) cause missorting to a constitutive pathway or impaired conversion of proinsulin to insulin, since a proportionately increased proinsulin release does not occur. Although the response of the secretory process to glucose-containing stimuli is almost completely destroyed, fractional secretion in response to nonglucose stimuli is enhanced. The possible contribution of hyperglycemia-induced beta-cell desensitization or specific lesions in the glucose recognition signals induced by MHC expression are discussed. Results suggest that expression of MHC class II protein causes highly specific beta-cell lesions which, in themselves, could be a contributing factor in human insulin-dependent diabetes.

Animals↗
PubMed1990

Loss of pancreatic islet tolerance induced by beta-cell expression of interferon-gamma.

Interferon-gamma (IFN-gamma) is produced during the response to infection and participates in immunostimulatory events. We have previously reported the induction of diabetes in transgenic mice (ins-IFN-gamma) in which the expression of the lymphokine IFN-gamma is directed by the insulin promoter. This diabetes is a result of the progressive destruction of pancreatic islets that occurs with the influx of inflammatory cells. Here we demonstrate that this islet cell loss is mediated by lymphocytes, that engrafted histocompatible islets are destroyed, and that lymphocytes from the transgenic mice are cytotoxic to normal islets in vitro. These results indicate that the pancreatic expression of IFN-gamma can result in a loss of tolerance to normal islets, consistent with its role as an inducer of costimulatory activity, which is essential for lymphocyte activation during an immune response.

Animals↗
PubMed1990

Interferon-gamma and the sexual dimorphism of autoimmunity.

The sexual difference in the incidence of autoimmune diseases has remained an enigma for many years. In the examination of the induction of autoimmunity in transgenic mice, evidence has been obtained further implicating the lymphokine interferon-gamma in the etiology of autoimmunity. Sex steroid regulation of the production of this molecule, as well as other cytokines, may help explain the gender-specific differences in the immune system, including autoimmunity.

Animals↗
PubMed1989

A mouse chromosome 17 gene encodes a testes-specific transcript with unusual properties.

We have characterized a novel mouse gene (D17Si11) on chromosome 17 that expresses a major transcript observed uniquely in the testes. The D17Si11 locus has been mapped to the central region of chromosome 17 between H-2 and C3. Sequence analysis demonstrates several unusual features of this locus and its transcript: first is the presence of complementary sets of alternating purine and pyrimidine residues within the 3' region of the transcript that could form double-stranded, hairpin-like secondary structures with properties similar to that of Z-DNA; second is the existence of a hypothetical, long open reading frame in the nucleotide strand that is complementary to the testes transcripts. This complementary strand open reading frame is three times the size of the longest potential open reading frame present in the transcript itself. Although a function for D17Si11 has yet to be determined, the gene is relatively nonpolymorphic in mice and appears conserved in mammals.

Amino Acid Sequence↗