Pancreatic Islets Of NOD Mice Research Articles

A Targeted Deep Sequencing Method to Quantify Endogenous Retrovirus Gag Sequence Variants and Open Reading Frames Expressed in Nonobese Diabetic Mice.

Endogenous retroviruses (ERVs) are involved in autoimmune diseases such as type 1 diabetes (T1D). ERV gene products homologous to murine leukemia retroviruses are expressed in the pancreatic islets of NOD mice, a model of T1D. One ERV gene, Gag, with partial or complete open reading frames (ORFs), is detected in the islets, and it contains many sequence variants. An amplicon deep sequencing analysis was established by targeting a conserved region within the Gag gene to compare NOD with T1D-resistant mice or different ages of prediabetic NOD mice. We observed that the numbers of different Gag variants and ORFs are linked to T1D susceptibility. More importantly, these numbers change during the course of diabetes development and can be quantified to calculate the levels of disease progression. Sequence alignment analysis led to identification of additional markers, including nucleotide mismatching and amino acid consensus at specific positions that can distinguish the early and late stages, before diabetes onset. Therefore, the expression of sequence variants and ORFs of ERV genes, particularly Gag, can be quantified as biomarkers to estimate T1D susceptibility and disease progression.

Optimized protocol for shotgun label-free proteomic analysis of pancreatic islets.

Pancreatic islets are crucial in diabetes research. Consequently, this protocol aims at optimizing both the protein-extraction process and the proteomic analysis via shotgun methods for pancreatic islets. Six protocols were tested, combining three types of chemical extraction with two mechanical extraction methods. Furthermore, two protocols incorporated a surfactant to enhance enzymatic cleavage. The steps involved extraction and concentration of protein, protein quantification, reduction, alkylation, digestion, purification and desalination, sample concentration to ∼1 µl, and proteomic analysis using the mass spectrometer. The most effective protocol involves either a milder chemical extraction paired with a more intensive mechanical process, or a more robust chemical extraction paired with a gentle mechanical process, tailored to the sample's characteristics. Additionally, it was observed that the use of a surfactant proved ineffective for these types of samples. Protocol 5 was recently used with success to examine metabolic changes in pancreatic islets of non-obese diabetic mice exposed to low doses of fluoride ions (F-) and the primary pathways altered by the treatment.

Metabolic effect of low fluoride levels in the islets of NOD mice: integrative morphological, immunohistochemical, and proteomic analyses.

Fluoride (F) has been widely used to control dental caries, and studies suggest beneficial effects against diabetes when a low dose of F is added to the drinking water (10 mgF/L). This study evaluated metabolic changes in pancreatic islets of NOD mice exposed to low doses of F and the main pathways altered by the treatment. In total, 42 female NOD mice were randomly divided into two groups, considering the concentration of F administered in the drinking water for 14 weeks: 0 or 10 mgF/L. After the experimental period, the pancreas was collected for morphological and immunohistochemical analysis, and the islets for proteomic analysis. In the morphological and immunohistochemical analysis, no significant differences were found in the percentage of cells labelled for insulin, glucagon, and acetylated histone H3, although the treated group had higher percentages than the control group. Moreover, no significant differences were found for the mean percentages of pancreatic areas occupied by islets and for the pancreatic inflammatory infiltrate between the control and treated groups. Proteomic analysis showed large increases in histones H3 and, to a lesser extent, in histone acetyltransferases, concomitant with a decrease in enzymes involved in the formation of acetyl-CoA, besides many changes in proteins involved in several metabolic pathways, especially energy metabolism. The conjunction analysis of these data showed an attempt by the organism to maintain protein synthesis in the islets, even with the dramatic changes in energy metabolism. Our data suggests epigenetic alterations in the islets of NOD mice exposed to F levels comparable to those found in public supply water consumed by humans.

Aberrant expression of transglutaminase 2 in pancreas and thymus of NOD mice underscores the importance of deamidation in neoantigen generation.

Post-translational modifications can lead to a break in immune tolerance in autoimmune diseases such as type 1 diabetes (T1D). Deamidation, the conversion of glutamine to glutamic acid by transglutaminase (TGM) enzymes, is a post-translational modification of interest, with deamidated peptides being reported as autoantigens in T1D. However, little is known about how Tgm2, the most ubiquitously expressed Tgm isoform, is regulated and how tolerance against deamidated peptides is lost. Here, we report on the aberrant expression and regulation of Tgm2 in the pancreas and thymus of NOD mice. We demonstrate that Tgm2 expression is induced by the inflammatory cytokines IL1β and IFNγ in a synergistic manner and that murine pancreatic islets of NOD mice have higher Tgm2 levels, while Tgm2 levels in medullary thymic epithelial cells are reduced. We thus provide the first direct evidence to our knowledge that central tolerance establishment against deamidated peptides might be impaired due to lower Tgm2 expression in NOD medullary thymic epithelial cells, which together with the aberrantly high levels of deamidated peptides in NOD β-cells underscores the role of deamidation in amplifying T-cell reactivity.

Identification of Novel Disease-Relevant Genes and Pathways in the Pathogenesis of Type 1 Diabetes: A Potential Defect in Pancreatic Iron Homeostasis.

Multiple pathways contribute to the pathophysiological development of type 1 diabetes (T1D); however, the exact mechanisms involved are unclear. We performed differential gene expression analysis in pancreatic islets of NOD mice versus age-matched congenic NOD.B10 controls to identify genes that may contribute to disease pathogenesis. Novel genes related to extracellular matrix development and glucagon and insulin signaling/secretion were changed in NOD mice during early inflammation. During "respective" insulitis, the expression of genes encoding multiple chemosensory olfactory receptors were upregulated, and during "destructive" insulitis, the expression of genes involved in antimicrobial defense and iron homeostasis were downregulated. Islet inflammation reduced the expression of Hamp that encodes hepcidin. Hepcidin is expressed in β-cells and serves as the key regulator of iron homeostasis. We showed that Hamp and hepcidin levels were lower, while iron levels were higher in the pancreas of 12-week-old NOD versus NOD.B10 mice, suggesting that a loss of iron homeostasis may occur in the islets during the onset of "destructive" insulitis. Interestingly, we showed that the severity of NOD disease correlates with dietary iron intake. NOD mice maintained on low-iron diets had a lower incidence of hyperglycemia, while those maintained on high-iron diets had an earlier onset and higher incidence of disease, suggesting that high iron exposure combined with a loss of pancreatic iron homeostasis may exacerbate NOD disease. This mechanism may explain the link seen between high iron exposure and the increased risk for T1D in humans.

Insulin specific TCR repertoire analysis reveals functional diversity of Treg TCRs

Abstract Regulatory T cells (Tregs) are critical in preventing autoimmunity and express a unique TCR repertoire with high affinity to self-antigens. However, whether Treg and effector T cell (Teff) TCR repertoires are similarly divergent in the context of autoimmunity, and whether Tregs are able to maintain TCR affinity advantage has not been clearly defined. Insulin tetramer positive Tregs isolated from pancreatic islets of NOD mice showed a higher level of self-reactivity (CD5) and TCR signaling (Nur77-GFP) than Teffs specific to the same epitope. We isolated and sequenced insulin tetramer+ Teffs and Tregs from islets of NOD mice expressing a fixed TCRα of an insulin specific TCR. Surprisingly, significant overlap was identified between Treg and Teff TCR repertoires, suggesting that similar TCRs can support autoimmune Treg and Teff development and recruitment into the autoimmune response. Both Tregs and Teffs exhibited TCRs with a broad range of reactivity to insulin epitope and Treg TCRs did not show increased reactivity. The disconnect between Nur77-GFP and TCR functional affinity suggests a Treg cell-intrinsic capacity to compete for antigen or to enhance downstream signaling. When re-expressed in vivo using the TCR retrogenic method, Treg derived TCRs showed lower Treg generation and collectively higher diabetogenicity. With comparable Treg generation, low affinity Treg TCR showed significantly lower protection against diabetes than high affinity Treg TCR. These findings indicate that in tissue specific autoimmunity Tregs can express a TCR repertoire with a broad range of functionality and have significant overlap with Teffs of the same specificity, which might negatively affect their suppressive capacity. This work was supported by the NIH (AI125301-01A1) and The Robert and Janice McNair Foundation.

SUN-658 CHL1 Increases Insulin Secretion&Negatively Regulates the Poliferation of Pancreatic β Cell

CHL1 Increases Insulin Secretion & Negatively Regulates The Poliferation Of Pancreatic β Cell Objective: CHL1 belongs to neural recognition molecules of the immunoglobulin superfamily, is mainly expressed in the nervous system. CHL1 is involved in neuronal migration, axonal growth, and dendritic projection. RNA sequencing of single human islet cells confirmed that CHL1 had an expression difference in β cells of type 2 diabetes and healthy controls. However, whether CHL1 gene regulates islet function remained to be explored. Methods: PCR and Western Blot were applied to investigate the tissue distribution of CHL1 in wild-type C57BL/6J mice. The islet expression of CHL1 gene was observed in pancreatic islets of NOD mice and high-fat-diet C57BL/6J mice of different ages. MIN6 cells with siRNA to silence CHL1 or with lentivirus to overexpress CHL1 were constructed. Effects of the gene on proliferation, apoptosis, cell cycle and insulin secretion were determined by using CCK8, EdU, TUNEL, AV/PI, GSIS, electron microscopy and flow cytometry. Results: CHL1 was localized on the cell membrane and expressed in the nervous system, islet of pancreas and gastrointestinal tract. CHL1 was hypoexpressed in the pancreatic islets of obese mice, hyperexpressed in the pancreatic islets of NOD mice and in vitro after treated with cytokines. After silencing CHL1 in MIN6 cells, insulin secretion decreased in 20 mM glucose with down-regulation of INS1, SLC2A2 gene, and transmission electron microscope showed the number of insulin secretary granules <50nm from the cell membrane was significantly reduced. Silencing of CHL1 in MIN6 cells induced cell proliferation, reduced apoptosis rate, prolonged the S phase of cell cycle and shortened the G1 phase with downregulated expression of p21, p53 and up-regulated expression of cyclin D1, opposite results were found in CHL1 over-expressing MIN6 cells. Proliferation induced by silencing of CHL1 was inhibited by ERK inhibitor (PD98059), which indicates that ERK pathway is essential for signaling by these molecules in pancreatic β cell. Conclusion: The expression of CHL1 gene was significantly decreased in the pancreatic islets of obese mice induced by high-fat diet. The low expression of CHL1 gene promotes the proliferation of MIN6 cells through the ERK pathway and affect cell cycle through the p53 pathway. This may be one of the mechanisms that pancreatic β cells compensatory hyperplasia in the stage of obesity-induced pre-diabetes.

Pharmacological Inhibition of Neutrophil Elastase Attenuates Insulitis and Autoimmune Diabetes in Mice

Background: Type 1 diabetes is an autoimmune disease resulted from self-destruction of insulin-producing pancreatic beta-cells. However, the pathological pathways that trigger the autoimmune destruction remain poorly understood. Our previous studies demonstrated that increased circulating neutrophil elastase (NE) is closely associated with beta-cell autoimmunity in patients with T1D. Here we investigate the role and mechanism whereby NE participates in the pathogenesis of T1D, and to explore the therapeutic potential of the pharmacological NE inhibitors for autoimmune diabetes. Method: Biochemical and immunological analysis were adopted to determine the dynamic change in the infiltration and activation of neutrophils in pancreas of NOD mice. NE-specific endogenous (pre-elafin/elafin) or pharmaceutical (sivelestat) inhibitors were supplemented into NOD mice to evaluate their effects on diabetes incidence and insultitis. Flow cytometry was employed to explore the effects of NE in mediating the crosstalk of immune cells. Results: A dynamic change in the infiltration of neutrophils was observed in pancreatic islets of NOD mice, leading to a transient elevation of local NE activity. Supplementation of NE-specific inhibitors rectified the elevated pancreatic NE activity, alleviated insulitis and reduced the development of T1D in NOD mice. Inhibition of NE activity significantly attenuated the infiltration of pro-inflammatory macrophages into pancreas, reduced the production of inflammatory cytokines. In vitro studies showed that NE directly induced inflammatory responses in both min6 beta-cells and RAW264.7 macrophages through the activation of TLR4-IκB-NFκB pathway. Discussion: NE-mediated crosstalk between beta-cell and macrophages forms a vicious feedback loop, resulting in the exaggerated beta-cell damage in NOD mice. Pharmacological inhibition of NE may represent a promising therapeutic strategy for treatment of autoimmune diabetes. Disclosure S. Lingling: None. L. Zhong: None. R. Hoo: None. A. Xu: None.

Transgenic expression of murine chemokine decoy receptor D6 by islets reveals the role of inflammatory CC chemokines in the development of autoimmune diabetes in NOD mice

Autoimmune diabetes results from a progressive destruction of insulin-producing beta cells in the pancreatic islets by chemokine-attracted lymphocytes. Because islet cells in NOD mice produce chemokines during the development of autoimmune diabetes, we investigated the role of inflammatory CC chemokines in disease progression in these mice. We generated a transgenic NOD mouse model that overproduces the inflammatory CC chemokine decoy receptor D6 in pancreatic islets. The frequency of diabetes and insulitis scores of transgenic mice were decreased significantly, compared with non-transgenic control littermates. Transgenic expression of D6 (also known as Ccbp2) did not affect systemic lymphocyte development or alter: (1) the T cell subsets such as T helper (Th)1, Th2 and T regulatory cells; or (2) antigen-presenting cells such as dendritic cells or macrophages. The percentages and numbers of T and B lymphocytes were decreased significantly in the pancreas. Activation status, autoantigen-specific proliferation and diabetogenicity of lymphocytes were also markedly reduced. Inflammatory CC chemokines play a critical role in the development of autoimmune diabetes. Transgenic expression of D6 in pancreatic islets of NOD mice reduced this pathogenic process by suppressing activation of autoreactive lymphocytes and by reducing migration of lymphocytes to the pancreas.

Islet Expression of M3 Uncovers a Key Role for Chemokines in the Development and Recruitment of Diabetogenic Cells in NOD Mice

Type 1 diabetes is an autoimmune disease characterized by a local inflammatory reaction in and around islets followed by selective destruction of insulin-secreting beta-cells. We tested the hypothesis that chemokines affect different mechanisms responsible for the development of diabetes in NOD mice. We examined chemokine expression in islets of NOD mice and tested their functional relevance to development of diabetes using transgenic mice expressing the mouse herpesvirus 68-encoded chemokine decoy receptor M3 (NOD-M3 mice) in insulin-secreting beta-cells. Multiple chemokines were expressed in pancreatic islets of NOD mice before development of diabetes. Islet-specific expression of the pan-chemokine inhibitor M3 dramatically reduced leukocyte infiltration and islet destruction and completely blocked development of diabetes in NOD-M3 mice. M3 blocked diabetes by inhibiting the priming of diabetogenic cells in the pancreatic lymph nodes and their recruitment into the islets. This effect was specific to the pancreatic islets because M3 expression did not affect other ongoing autoimmune processes. These results demonstrate that chemokines mediate afferent and efferent immunity in type 1 diabetes and suggest that broad chemokine blockade may represent a viable strategy to prevent insulitis and islet destruction.

Expression of interferon inducible protein-10 in pancreas of mice

To investigate the expression of interferon inducible protein-10 (IP-10) in pancreas of mice and to discuss its possible role in the pathogenesis of type 1 diabetes. Non-obese diabetic (NOD) mice were used as experiment group and BALB/c mice as non-diabetic prone model. Immunohistochemistry method was used to evaluate the expression of IP-10 in the pancreas of NOD mice and BALB/c mice. Immunoelectron microscope was used to show the location of IP-10 in pancreatic islet beta cells. Pancreatic islets were positively stained in all the NOD mice. Insulitis could be found in mice at the age of 4 wk. The weakly positive results were found in control group with no insulitis. Immunoelectron microscopy further demonstrated that IP-10 was produced by pancreatic beta cells and stored in cytoplasm of the cells. IP-10 can be largely produced in pancreatic islets of NOD mice at the age of 2 wk when there is no significant insulitis, and may play an important part in the pathogenesis of type 1 diabetes by attracting immune cells to infiltrate the pancreatic islets.

Immunolocalization of caspase-3 in pancreatic islets of NOD mice during cyclophosphamide-accelerated diabetes.

Apoptosis may be a major mechanism of beta cell loss during insulin-dependent diabetes mellitus. Caspase-3 is a key enzyme involved in the terminal steps of this death process. Here, the intra-islet expression of caspase-3 in the NOD mouse was examined immunohistochemically following acceleration of the disease with cyclophosphamide. Female NOD mice were treated at day 95 with cyclophosphamide, and caspase-3 expression in pancreatic sections was studied at days 0, 4, 7, 11, and 14 and compared with age-matched control tissue. In the treated group at day 0, caspase-3 labeling was seen in several peri-islet macrophages and only extremely rarely in beta cells. At day 4, only a few beta cells weakly expressed the enzyme. From day 7, caspase-3 expression began to increase in intra-islet macrophages and reached a peak at days 11 and 14, when a small number of CD4 and CD8 T cells also showed positive labeling. Beta cell expression of caspase-3 at days 11 and 14 was rare. At this stage, several intra-islet immune cells with positive labeling for the enzyme coexpressed either Fas or interleukin-1beta. Only a small proportion of intra-islet caspase-3 cells showed apoptotic nuclei judged by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL). We conclude that, during cyclophosphamide-accelerated diabetes, the predominant caspase-3 immunolabeling in intra- and extra-islet macrophages suggests that apoptosis of macrophages may be an important mechanism for their elimination. The virtual absence of caspase-3 immunolabeling in most beta cells even during the height of beta cell loss supports the need for developing other markers of early beta cell apoptosis in the NOD mouse.

Fas and Fas ligand immunolocalization in pancreatic islets of NOD mice during spontaneous and cyclophosphamide-accelerated diabetes.

During insulin-dependent diabetes mellitus, immune cells which infiltrate pancreatic islets mediate beta cell destruction over a prolonged asymptomatic prediabetic period. The molecular mechanisms of beta cell death in vivo remain unresolved. At least two major molecular processes of destruction have been proposed. One involves the Fas-FasL (Fas-Fas ligand) system and the other, the perforin pathway. Here, dual-label immunohistochemistry was employed to examine the intra-islet expression, distribution and cellular sources of Fas and FasL in the NOD mouse, during spontaneous diabetes (days 21, 40 and 90) and following acceleration of diabetes with cyclophosphamide (days 0, 4, 7, 11 and 14 after cyclophosphamide administration). The expression of the proteins was correlated with advancing disease. FasL was expressed constitutively in most beta cells but not in glucagon or somatostatin cells or islet inflammatory cells and paralleled the loss of insulin immunolabelling with advancing disease. It was also expressed in beta cells of non-diabetes prone CD-1 and C57BL/6 mice from a young age (day 21). Strong immunolabelling for Fas was first observed in extra-islet macrophages and those close to the islet in NOD and non-diabetes-prone mice. During spontaneous and cyclophosphamide diabetes, it was observed in a higher proportion of islet infiltrating macrophages than CD4 and CD8 T cells, concomitant with advancing insulitis. In cyclophosphamide-treated mice, the proportion of Fas-positive intra-islet CD4 and CD8 T cells at day 14 (with and without diabetes) was considerably higher than at days 0, 4, 7 and 11. At days 11 and 14, a proportion of Fas-positive intra-islet macrophages co-expressed interleukin-1beta and inducible nitric oxide synthase. Fas was not detectable in beta cells and other islet endocrine cells during spontaneous and cyclophosphamide induced diabetes. Our results show constitutive expression of FasL in beta cells in the NOD mouse and predominant expression of Fas in intra-islet macrophages and to a lesser extent in T cells prior to diabetes onset. Interleukin-1beta in intra-islet macrophages may induce Fas and inducible nitric oxide synthase expression in an autocrine and paracrine manner and mediate beta cell destruction or even death of some macrophages and T cells. However, other mechanisms of beta cell destruction during spontaneous and cyclophosphamide-accelerated diabetes and independent of Fas-FasL, require examination.

Immunoexpression of interleukin-1beta in pancreatic islets of NOD mice during cyclophosphamide-accelerated diabetes: co-localization in macrophages and endocrine cells and its attenuation with oral nicotinamide.

During insulin-dependent diabetes mellitus, islet invading immune cells destroy beta cells over a prolonged asymptomatic pre-diabetic period. Cytokines synthesised and secreted by specific immune cells within the islet infiltrate may be crucial effectors of beta cell destruction or protection during the disease. Interleukin-1beta may be a key cytokine which may act in concert with other cytokines in initiating and/or promoting beta cell destruction. We have examined this hypothesis in NOD mice by assessing the intra-islet expression and co-localization of interleukin-1beta at different time-points following cyclophosphamide administration. We have also tested the effects of long-term oral nicotinamide given to NOD mice in suppressing intra-islet expression of the cytokine in this accelerated model. Cyclophosphamide was administered to day 95 female NOD mice. Pancreatic tissues were examined by dual-label confocal immunofluorescence microscopy for the expression and co-localization of interleukin-1beta at days 0, 4, 7, 11 and at onset of diabetes (day 14). Diabetes developed in 7/11 mice 14 days after administration of cyclophosphamide while nicotinamide completely prevented the disease. At day 0, interleukin-1beta immunolabelling was observed in selective intra-islet macrophages, several somatostatin cells and in a few beta cells. However, at day 4, it was seen mostly in somatostatin and some beta cells. At day 7, an increasing number of interleukin-1beta cells were observed within the islets and co-localized to several somatostatin cells, beta cells and macrophages. The mean number of intra-islet interleukin-1beta cells reached a peak at day 11 and was significantly higher than at day 7 (p = 0.05) and at day 14 (onset of diabetes; p = 0.03). At day 11, interleukin-1beta immunolabelling was also present in selective macrophages which co-expressed inducible nitric oxide synthase. At onset of diabetes, some macrophages, residual beta cells and somatostatin cells showed immunolabelling for the cytokine. Exposure of NOD mice to oral nicotinamide was associated with a considerably reduced expression of interleukin-1beta cells within the islet at day 11 (p = 0.002). We conclude that cylophosphamide treatment enhances the expression of interleukin-1beta in selective macrophages, somatostatin and beta cells during the course of the disease. Its expression reaches a maximum immediately prior to onset of diabetes. Interleukin-1beta present in intra-islet macrophages, somatostatin and beta cells may influence its expression by autocrine and paracrine means. Interleukin-1beta expression within islet macrophages may also up-regulate inducible nitric oxide synthase within the same macrophage or adjacent macrophage populations. These intra-islet molecular events may corroborate with other local cytotoxic processes leading to beta cell destruction. Oral nicotinamide may attenuate intra-islet expression of interleukin-1beta and thus inducible nitric oxide synthase during prevention of Type 1 diabetes in this animal model. The expression of interleukin-1beta in specific islet endocrine cell-types shown in this study requires further investigation.

Temporal relationship between immune cell influx and the expression of inducible nitric oxide synthase, interleukin-4 and interferon-gamma in pancreatic islets of NOD mice following adoptive transfer of diabetic spleen cells.

Beta cell destruction in NOD mice can be accelerated by adoptive transfer of diabetic spleen cells into irradiated adult NOD mice. Here mice receiving diabetic spleen cells were examined at days 0, 7, 14, 21 and at onset of diabetes for the resulting insulitis and the number of intra-islet CD4 and CD8 cells and macrophages. The progression of insulitis and the number of intra-islet CD4 and CD8 cells and macrophages were correlated with the expression and co-localization of inducible nitric oxide synthase, interferon-gamma and interleukin-4 by dual-label light and confocal immunofluorescence microscopy. Diabetes developed in 7/8 mice by 27 days following cell transfer. The insulitis score increased slightly by day 7 but rose sharply at day 14 (p = 0.001) and was maintained until diabetes. The mean number of intra-islet CD4 and CD8 cells and macrophages showed a similar trend to the insulitis scores and were present in almost equal numbers within the islets. Immunolabelling for inducible nitric oxide synthase was observed at day 7 in only some cells of a few islets but increased sharply from day 14. It was restricted to islets with insulitis and was co-localized in selective macrophages. Weak intra-islet interleukin-4 labelling was observed at days 7 and 14 but became more pronounced at day 21 and at onset of diabetes, being present in selective CD4 cells. Intra-islet labelling for interferon-gamma was first observed at day 21, but became more intense at onset of diabetes and was co-localized in a proportion of macrophages. Both cytokines were expressed in islets with advanced insulitis. Interferon-gamma staining was also observed within endothelial cells located in the exocrine pancreas. We conclude that transfer of diabetic spleen cells results in a rapid influx of CD4 and CD8 cells and macrophages within the pancreas of recipient mice. During the period of heightened insulitis, selective immune cells begin to express inducible nitric oxide synthase and the opposing cytokines, interferon-gamma and interleukin-4. Expression of these molecules becomes more pronounced immediately prior to and during the onset of diabetes.

Exclusive expression of MHC class II proteins on CD45+ cells in pancreatic islets of NOD mice

Exclusive expression of MHC class II proteins on CD45+ cells in pancreatic islets of NOD mice

Exclusive Expression of MHC Class II Proteins on CD45+ Cells in Pancreatic Islets of NOD Mice

The expression of MHC class II molecules on beta-cells of the pancreatic islet has been proposed to play a role in the genesis of insulin-dependent diabetes mellitus in the NOD mouse. We investigated this by immunofluorescent double labeling of islet cells with anti-MHC and anti-CD45 to identify cells of hematopoietic origin. MHC class I expression increased with age on CD45- islet cells. MHC class II expression was not observed on CD45- islet cells at any age; the only cells in the islet that were MHC class II positive were also CD45+. This indicates that all MHC class II-positive cells in the islet are lymphoid cells that infiltrate the islet, whereas the islet endocrine cells express no MHC class II molecules. However, an increase in MHC class I expression occurred on beta-cells, and this may play a role in immunopathogenesis.

Cytotoxic T lymphocytes from pancreatic islets of NOD mice

Cytotoxic T lymphocytes from pancreatic islets of NOD mice