Mechanisms of autoimmunity: relevance to the pathogenesis of type I (insulin-dependent) diabetes mellitus

Local expression of transgene encoded TNF alpha in islets prevents autoimmune diabetes in nonobese diabetic (NOD) mice by preventing the development of auto-reactive islet-specific T cells

Lately, TNF alpha has been the focus of studies of autoimmunity; its role in the progression of autoimmune diabetes is, however, still unclear. To analyze the effects of TNF alpha in insulin-dependent diabetes mellitus (IDDM), we have generated nonobese diabetic (NOD) transgenic mice expressing TNF alpha under the control of the rat insulin II promoter (RIP). In transgenic mice, TNF alpha expression on the islets resulted in massive insulitis, composed of CD4+ T cells, CD8+ T cells, and B cells. Despite infiltration of considerable number of lymphoid cells in islets, expression of TNF alpha protected NOD mice from IDDM. To determine the mechanism of TNF alpha action, splenic cells from control NOD and RIP-TNF alpha mice were adoptively transferred to NOD-SCID recipients. In contrast to the induction of diabetes by splenic cells from control NOD mice, splenic cells from RIP-TNF alpha transgenic mice did not induce diabetes in NOD-SCID recipients. Diabetes was induced however, in the RIP-TNF alpha transgenic mice when CD8+ diabetogenic cloned T cells or splenic cells from diabetic NOD mice were adoptively transferred to these mice. Furthermore, expression of TNF alpha in islets also downregulated splenic cell responses to autoantigens. These data establish a mechanism of TNF alpha action and provide evidence that local expression of TNF alpha protects NOD mice from autoimmune diabetes by preventing the development of autoreactive islet-specific T cells.

Heterogeneity of autoantibodies in stiff-man syndrome

Stiff-man syndrome is a rare neurological disorder characterized by skeletal muscle rigidity and spasms in which detection of circulating anti-glutamic acid decarboxylase antibodies has suggested an autoimmune pathogenesis. To further define the role of autoimmunity in the pathogenesis, we studied anti-glutamic acid decarboxylase antibodies, as well as organ- and non-organ-specific autoantibodies in 13 patients with stiff-man syndrome and 127 patients with other neurological disorders. Thyrogastric antibodies were more frequent in patients with stiff-man syndrome (46%) than in those with other neurological disorders (12%) (p < 0.05). Non-organ-specific antibodies were found at a similar frequency in the patients with stiff-man syndrome (61%) and those with other neurological disorders (65%). Islet-cell autoantibodies and anti-glutamic acid decarboxylase antibodies were more common in stiff-man syndrome patients (38% and 31%) compared to the patients with other neurological disorders (6% and 3%, respectively; p < 0.001). With the exception of 1 patient in the other neurological disorders group, anti-glutamic acid decarboxylase antibodies were always associated with islet-cell autoantibodies. Four patients with stiff-man syndrome had an associated solid tumor: 3 of them had antibodies recognizing a 125/130-kd protein and not glutamic acid decarboxylase.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of a short prednisone regime at clinical onset of type 1 diabetes

The effect of corticosteroids on beta cell function and humoral immune response in type 1 diabetes was tested in a 2-month trial conducted on 32 newly diagnosed patients (age 22.8 +/- 1.4 years, mean +/- S.E.M.). Prednisone was administered at immunosuppressive dosage (1 mg.kg-1.day-1) during the initial 10 days and at a maintenance dosage (0.3 mg.kg-1.day-1) for 50 days. Patients (n = 32) were enrolled within 6 weeks after diagnosis and matched in pairs for age, sex, presence of islet cell antibodies (ICA) and glucagon stimulated C-peptide levels. Insulin discontinuation was not contemplated. All the patients who received prednisone became ICA during treatment but in some (4 out of 10) this effect was only transient. Insulin antibodies (IA) were significantly lower in the prednisone group at second and third month (P < 0.05). No patient experienced complete remission but in 10 prednisone and 4 control patients the insulin requirements were below 0.3 IU/kg (P < 0.05). With similar glycemia the fasting C-peptide levels were higher in the treated patients. The profile of the insulin requirements during the follow-up was different in the two groups and at 9 months the prednisone group needed less insulin than the control (P < 0.05). Interestingly, within the prednisone-treated group and after 6 months, the levels of stimulated C-peptide improved significantly among the ICA+ patients while they were steady or declined in ICA- (P < 0.01). The analysis of variance covariance confirmed a positive interaction between ICA and the administration of prednisone on the outcome of beta cell function.(ABSTRACT TRUNCATED AT 250 WORDS)

In search of predictive markers of remission from insulin dependence in type 1 diabetes: a preliminary report

We studied 18 newly diagnosed diabetic patients (8 males and 10 females, aged 18-26 years, within 10-120 days from the onset of symptoms) who were submitted for 15 days to intensive insulin therapy performed via subcutaneous insulin infusion (CSII). We investigated some metabolic and immunological parameters in order to identify a possible marker to predict the selection of patients potentially more responsive to CSII treatment for the remission of type 1 diabetes. In accordance with the International Diabetes Immunology Group we considered clinical remission as being the withdrawal of insulin therapy for at least 3 months. In order to assess beta-cell function a fasting and post-prandial serum C-peptide, blood glucose and HbA1c were performed on all patients before, and 3 days after, the discontinuation of CSII. Islet cell antibodies were determined in all sera by indirect immunofluorescence. Analysis of T-lymphocyte subpopulations was carried out before starting the therapy. The following monoclonal antibodies were used: CD4, CD8, CD57, CD25, HLA-DR. The levels of C3 and C4 and serum IgG, IgA and IgM were also evaluated. After CSII, 11 of 18 patients showed remission. At the beginning of the study we observed no major difference in metabolic parameters between the two groups. Interestingly, the patients who exhibited remission presented a statistically higher percentage of positive cells for CD57, HLA-DR and CD25 surface antigens, significantly lower C4 levels and CD4/CD8 ratio and significantly higher IgG levels compared with patients who did not show any remission.(ABSTRACT TRUNCATED AT 250 WORDS)

Islet-cell antibodies and endogenous insulin secretion in Sudanese diabetic children

Cytoplasmic islet-cell antibodies (ICA) and endogenous insulin secretion were studied in 46 Sudanese children (mean age 11.6 years) with newly diagnosed insulin-dependent diabetes mellitus (IDDM). Islet-cell antibodies were detected both by the indirect immunofluorescence (IF) and complement fixation (CF) methods. Endogenous insulin levels were measured as C-peptide concentration using radio-immunoassays. The degree of metabolic control of diabetics was judged by the presence of diabetic ketoacidosis (DKA) at onset, glycated haemoglobin (HbA1c) level and insulin requirement, expressed as dose per kg body weight per day, at the time of presentation. Twenty-nine patients (63%) had either IF-ICA or CF-ICA or both in their sera. These figures are significantly higher than those reported for African populations. Islet-cell antibody positive patients had significantly lower C-peptide concentration, higher HbA1c level, higher insulin requirement and higher prevalence of ketoacidosis at presentation. Furthermore, the C-peptide levels were higher in CF-ICA positive patients than in subjects who showed only IF-ICA positivity. Our findings show a clear association between ICA and severity of diabetes at clinical onset and also suggest that the presence of CF-ICA at or shortly after diagnosis of IDDM is indicative of preservation of some functioning beta-cell mass.

Loss of regular oscillatory insulin secretion in islet cell antibody positive non-diabetic subjects

Basal insulin secretion was compared in nine islet-cell antibody positive, non-diabetic first-degree relatives of children with Type 1 (insulin-dependent) diabetes mellitus and nine normal control subjects matched for age, sex and weight. Acute insulin responses to a 25 g intravenous glucose tolerance test were similar in the two groups (243 (198-229) vs 329 (285-380) mU.l-1 x 10 min-1, mean (+/- SE), p = 0.25). Fasting plasma insulin was assayed in venous samples taken at one min intervals for 2 h. Time series analysis was used to demonstrate oscillatory patterns in plasma insulin. Autocorrelation showed that regular oscillatory activity was generally absent in the islet-cell antibody-positive group, whereas a regular 13 min cycle was shown in control subjects (p less than 0.0001). Fourier transformation did, however, show a 13 min spectral peak in the islet-cell antibody positive group, consistent with intermittent pulsatility. We conclude that overall oscillatory patterns of basal insulin secretion are altered in islet-cell antibody positive subjects even when the acute insulin response is within the normal range.

Early T-cell defects in pre-type 1 diabetes

Alterations of lymphocyte subsets have been recently reported in pre-type 1 diabetes but the relation with other immunological markers, in particular islet cell antibodies (ICA), is still unknown. In the present study, we have investigated prospectively changes of lymphocyte subsets in 86 first-degree relatives of patients affected by type 1 diabetes and correlated such modifications with ICA titres. Among individuals with persistent ICA, 8 had ICA titres of more than 20 JDF units, 14 had ICA titres between 5 and 20 JDF units and 64 had ICA titres between 0 and 5 JDF units. First-degree relatives with ICA titres of more than 20 JDF units had significantly decreased proportions of CD3 cells. This reduction was predominantly in the CD4 subset, giving rise to a decreased CD4/CD8 lymphocyte ratio. Those with ICA titres between 5 and 20 JDF units showed abnormalities in both CD3 and CD4 lymphocytes, but not in CD4/CD8 lymphocyte ratio. Further characterization of the CD4 cell subset was performed using three other monoclonal antibodies, CD45RO (UCHL1), CD45RA and CD29, phenotyping memory T-cells, the inducer cells of suppressor function and helper-inducer cells, respectively. The proportions of total CD45RO and CD45RA were not significantly different among first-degree relative with distinct ICA titres in a cross-sectional study, whereas a trend towards a reduced proportion of CD4/CD45RA cells was observed. The longitudinal study demonstrated that individuals potentially susceptible to the development of type 1 diabetes and who possess high titres of ICA have impairment of CD4/CD8 lymphocyte ratio, mainly due to a reduction in the CD4 subset.(ABSTRACT TRUNCATED AT 250 WORDS)

Autoantibodies to glutamic acid decarboxylase (GAD) detected by an immuno-trapping enzyme activity assay: relation to insulin-dependent diabetes mellitus and islet cell antibodies

It has recently been proposed that the islet 64,000 Mr protein autoantigen (64K) of insulin-dependent diabetes mellitus (IDDM) is glutamic acid decarboxylase (GAD). We evaluated, by means of a newly developed immunotrapping enzyme activity assay (ITEAA), the prevalence of circulating GAD-autoantibodies (Ab) in a large population of IDDM patients (n = 168), blood donors (n = 87) and non-diabetic autoimmune patients (n = 40). The latter two groups were used as controls. Overall, GAD-Ab were found in 22% of IDDM patients, but in none of the two control groups (P = 0.007). These specificities were invariably associated with islet cell antibodies (ICA) (31.6% in IDDM with ICA vs 0 in IDDM without ICA, P = 0.0001), and this prevalence was higher in sera with high titer ICA (54.5% in IDDM with ICA greater than 80 JDF-units vs 22.6% of IDDM with ICA 5-80 JDF units; P = 0.002). Moreover, GAD-Ab were associated with the female sex (P = 0.002) and the concomitant presence of thyroid and/or gastric antibodies (P = 0.002). No correlation was observed between GAD-Ab and age of the patients, duration of IDDM, or associated non-organ specific antibodies. Our study indicates that GAD-Ab measured by ITEAA are: (1) detected in a proportion of IDDM patients; (2) strongly associated with ICA; (3) preferentially found in IDDM female patients with autoimmune polyendocrine serology; and (4) detected with lower frequency than that reported for 64K-Ab in IDDM.

Novel considerations on the antibody/autoantigen system in type I (insulin-dependent) diabetes mellitus

Insulin dependent diabetes (IDDM) has an autoimmune pathogenesis. Included is the presence of antibodies to pancreatic islet cells. The first identified were islet cell antibodies (ICA), detected by indirect immunofluorescence, and which react with all cells within islets. Importantly, the autoantibodies are found several years prior to disease and although a pathogenic role for the autoantibodies is unclear, they have become useful markers of prediabetes. A number of studies of twins discordant for IDDM and of first degree relatives of IDDM patients have established that there is an increased risk for disease in individuals who have ICA, especially when ICA levels are high. This high predictive value of ICA decreases in the general population where the incidence of IDDM is lower than in first degree relatives, and both ICA and the disease risk associated with ICA, appear to be influenced by a genetic susceptibility. This has been sustained in a study of patients with endocrine autoimmunity and ICA (Polyendocrine Study) where the predictive value of very high levels of ICA is less than 50% in patients without a first degree relative with IDDM. Hence, there remain a substantial number of patients with ICA who do not develop disease. From these patients, it was demonstrated that ICA include at least two distinct specificities, one of which is beta cell specific and is not associated with a high risk for IDDM.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of viruses in the pathogenesis of IDDM

Insulin-dependent diabetes mellitus (IDDM), also known as type I diabetes, results from the destruction of pancreatic beta cells. During the past few decades, genetic factors, autoimmunity and viral infections have been extensively studied as the possible cause of beta cell destruction. The evidence for virus-induced diabetes comes largely from experiments in animals, but several studies in humans also point to viruses as a trigger of this disease in some cases. There are at least two possible mechanisms for the involvement of viruses in the pathogenesis of IDDM: (a) cytolytic infection of beta cells may result in destruction of the cells without the induction of autoimmunity, or may be a final insult leading to the clinical onset of diabetes in individuals with an already decreased beta cell mass resulting from an autoimmune process; and (b) persistent viral infection (e.g. retrovirus, rubella virus, cytomegalovirus) may result in the triggering of autoimmune IDDM in certain circumstances. Regarding the latter possibility, viruses may insert, expose, or alter antigens in the plasma membrane of the beta cell, which may initiate autoimmunity leading to the destruction of the cells.

Islet cell antibodies are not specifically associated with insulin-dependent diabetes in Tanzanian Africans

The prevalence of islet cell antibodies (ICA and CF-ICA) together with other organ-specific auto-antibodies was investigated in 122 newly presenting black Tanzanian diabetic patients in Dar es Salaam. ICA were found in three (8.6%) IDDM patients and five (6.8%) insulin-requiring NIDDM patients; six of the eight were also CF-ICA positive. Altogether 22% of patients showed one or more positive autoantibody result but there was no clustering of response, and no association of ICA with other antibodies except for two NIDDM subjects who showed one other positive result. There were no differences between insulin-requiring (IDDM) and NIDDM subjects or between younger (less than 30 years) and older patients. We conclude that there is no major association between diabetes and islet cell antibodies in black Tanzanians.

The role of viruses and environmental factors in the induction of diabetes

The development of IDDM results from the destruction of pancreatic beta cells. Genetic factors, various immune system alterations, and environmental factors have been studied as the possible causes of IDDM. The concordance rate for developing IDDM between monozygotic twins approaches 50%, suggesting that genetic factors are necessary, but nongenetic factors such as various immune system alterations and environmental factors also influence the clinical expression of genetic susceptibility. Environmental factors (e.g., viruses, chemicals, and diet) affecting the induction of diabetes may act as primary injurious agents which damage pancreatic beta cells or as triggering agents of autoimmunity. Certain viruses including EMC-D and Mengo virus 2T can directly infect pancreatic beta cells and replicate in the cells. The replication of viruses in the beta cells results in the destruction of the cells within 3 days, and the infected mice develop a diabeteslike syndrome in 3-4 days without the involvement of autoimmunity. In contrast, rubella virus appears to be somewhat weakly associated with autoimmune IDDM in hamsters. In addition, endogenous retrovirus expressed in pancreatic beta cells is clearly associated with the development of insulitis and diabetes in NOD mice. In man, there appears to be no correlation between the detection of islet cell autoantibodies and anti-Coxsackie B viral antibodies in newly diagnosed IDDM. In contrast, persistent infection of CMV and rubella virus appears to be associated with the presence of autoantibodies in newly diagnosed IDDM patients. It is particularly noteworthy that human CMV can induce islet cell autoantibodies that react specifically with a 38 kDa islet cell protein which may represent islet cell-specific antigens in a proportion of CMV-associated IDDM cases. These observations suggest that the association of diabetes with Coxsackie B viruses might be due to cytolytic infection of the beta cells with no link to autoimmunity, while both rubella virus and CMV are probably associated with autoimmune IDDM. A number of structurally diverse chemicals including alloxan, streptozotocin, chlorozotocin, Vacor, and cyproheptadine are diabetogenic mainly in rodents and sometimes in man. Possible mechanisms for beta cell destruction by these chemicals include (a) generation of oxygen free radicals and alteration of endogenous scavengers of these reactive species; (b) breakage of DNA and a consequent increase in the activity of poly-ADP-ribose synthetase, an enzyme depleting nicotinamide adenine dinucleotide in beta cells; and (c) inhibition of active calcium transport and calmodulin-activated protein kinase activity. (ABSTRACT TRUNCATED AT 400 WORDS)

Lessons from the NOD mouse for the pathogenesis and immunotherapy of human type 1 (insulin-dependent) diabetes mellitus

Suitable animal models of human Type 1 (insulin-dependent) diabetes mellitus have long been sought, in particular a model that would permit detailed histological and immunological investigation of changes in the islet preceding the metabolic disorder. This would allow hypotheses as to pathogenesis of the condition to be examined and interventions such as immunotherapy to be tested. The most widely studied models include the low-dose streptozotocin induced diabetic mouse and the BB rat, but both differ in important respects from the human disease. In this review we describe one highly successful model, the non obese diabetic mouse. Selected aspects of pathogenesis and immunotherapy are presented and analogies with human Type 1 diabetes discussed.

TNF-alpha gene polymorphisms in type 1 (insulin-dependent) diabetes mellitus

Type 1 (insulin-dependent) diabetes mellitus, like some other autoimmune diseases, is linked to certain alleles coded by genes in the HLA-D region. Sequence analysis of DQ beta chains indicates that aspartic acid at codon 57 confers resistance to the development of Type 1 diabetes. However, a full explanation for the HLA-association of Type 1 diabetes, particularly the increased susceptibility of DR3/4 heterozygotes is still awaited. The localisation of tumour necrosis factor genes on the short arm of chromosome 6 between HLA-B and the complement genes (Class III) prompted us to investigate a possible polymorphism of TNF-alpha at the genomic level in relation to Type 1 diabetes susceptibility. A dialleleic TNF-alpha restriction fragment length polymorphism was found with Ncol and its segregation with HLA-haplotypes analysed in diabetic families. We describe here a strong linkage of TNF-alpha alleles with certain DR haplotypes. For example, the common extended haplotype HLA A1-B8-DR3 was almost exclusively associated with the 5.5 kb TNF-alpha allele whereas Bw62-DR4 with the 10.5 kb allele. Thus both alleles segregate to diabetic patients. DR matched haplotypes of affected family members differed significantly from those of the non-affected at the TNF alpha locus. All affected sibling pairs in 11 multiplex affected families were identical for TNF-alpha alleles, even if they were only haploidentical for HLA-B-DR haplotypes. In addition, heterozygosity for the TNF-alpha alleles was significantly more frequent in the patients. This tight linkage of TNF-alpha alleles with some extended haplotypes could help to explain the HLA-association of Type 1 diabetes as well as some other autoimmune diseases.

Ten-year follow-up study of islet-cell antibodies and childhood diabetes mellitus

To find out whether subclinical autoimmunity precedes onset of nonfamilial insulin-dependent diabetes mellitus (IDDM), 4806 schoolchildren aged 5-19 years from a township in Holland were followed-up for at least ten years after blood was sampled for measurement of islet-cell antibodies (ICA). ICA positivity conferred a relative risk of IDDM of 533 (95% CI 145-1955). In the 10 years of follow-up 4 of the 8 ICA-positive subjects became insulin dependent, whereas the probability of being free of IDDM was 99.9% for those who were ICA-negative at the start of the study. The findings suggest that, although chronic autoimmunity involving the pancreatic beta-cells may precede non-familial IDDM by many years, a positive ICA test on a single occasion predicts the development of IDDM in only 4 out of 8 subjects over a period of 10 years.

Retrovirus-like sequences in Graves' disease: implications for human autoimmunity

On Southern blotting of DNA extracted from thyroid glands of five patients with Graves' disease, two probes (720 bp and 942 bp) for gag human immunodeficiency virus type 1 (HIV-1) gave a positive hybridisation signal in all samples tested. DNAs from peripheral blood mononuclear cells hybridised with the 720 bp gag HIV-1 probe in three of the five patients, none of whom had antibodies to HIV-1. Negative results were obtained with DNA from normal thyroid glands, thyroid neoplasms, various unrelated normal tissues, and virus-infected human cell lines. The intensity of the signal and the pattern of bands observed with the DNA of Graves' patients were heterogeneous and, in general, were not the same in the thyroid glands and peripheral blood mononuclear cells of individual patients. Similarly, no correlation was found between the positive hybridisation signals and other genetic and immunological indices or the duration of anti-thyroid drug treatment at the time the patients were investigated. The findings suggest the presence of a novel retrovirus, and the retrovirus-like sequences seem to be closely associated with thyroid autoimmunity.

Effect of probucol on development of diabetes mellitus in BB rats

Insulin-dependent diabetes mellitus (IDDM) results from an inflammatory process leading to destruction of the insulin-producing beta cells of the pancreas. Genetically mediated autoimmune processes are considered the most likely explanation for IDDM in humans, while viral infections, toxic agents, nutritional alterations and stress are also considered possibilities. The precise mechanisms by which autoimmunity, infections, toxins or other agents produce beta cell damage are not known. Toxin-induced diabetes in animals can be prevented by antioxidant therapy, while an agent that inhibits hydroxyl radical formation, desferrioxamine, extends the survival time of free allotypic islets in nonobese diabetic mice. The BB/W rat develops IDDM secondary to a pervasive autoimmune defect. This well-studied animal model develops IDDM with a highly predictable frequency and timing. This study describes the effects of the potent antioxidant, probucol, on the development of diabetes in BB rats by introducing it into standard rat chow at a 1% concentration at the time of weaning, and continuing this feeding schedule through 160 days of life. Control rats from split litters received standard chow only. Diabetes developed in 86.2% of the control rats at a mean age of 90.4 days. Probucol administration was associated with a reduction to 62% and a delay in diabetes diagnosis to 99.6 days. These very preliminary results suggest that probucol may be altering the inflammatory process, resulting in beta cell destruction in these genetically diabetes-prone rats.

Predicting insulin-dependent diabetes

719 first-degree relatives of diabetic children were followed up to assess the value of HLA haplotype sharing and of islet-cell antibodies (ICA) for prediction of insulin-dependent diabetes (IDDM). Within a maximum of 8 years' follow-up (3384 patient-years of observation) 16 unaffected relatives (5 parents and 11 siblings) became insulin dependent. The cumulative risk of becoming insulin dependent by age 25 was 16% for siblings sharing two HLA haplotypes with the proband, 9% for those sharing one haplotype, and zero for those sharing none. 13 of 24 (54%) subjects positive for complement-fixing ICA on three or more occasions became insulin dependent, as against 1 of 30 (3%) with noncomplement-fixing ICA alone and 2 of 665 (0.3%) ICA-negative subjects; by life-table analysis the risks after 8 years of known ICA status are 76%, 3%, and 0.6%, respectively. In terms of total time at risk ICA-positive family members had a relative risk of 75.2 compared with ICA-negative individuals. With positivity for complement-fixing ICA the relative risk was 188.5.