A protective role of the environment in the development of type 1 diabetes?

Coming full circle in diabetes mellitus: from complications to initiation

Glycaemic control, reduction of blood pressure using agents that block the renin-angiotensin system and control of dyslipidaemia are the major strategies used in the clinical management of patients with diabetes mellitus. Each of these approaches interrupts a number of pathological pathways, which directly contributes to the vascular complications of diabetes mellitus, including renal disease, blindness, neuropathy and cardiovascular disease. However, research published over the past few years has indicated that many of the pathological pathways important in the development of the vascular complications of diabetes mellitus are equally relevant to the initiation of diabetes mellitus itself. These pathways include insulin signalling, generation of cellular energy, post-translational modifications and redox imbalances. This Review will examine how the development of diabetes mellitus has come full circle from initiation to complications and suggests that the development of diabetes mellitus and the progression to chronic complications both require the same mechanistic triggers.

The pathogenesis and natural history of type 1 diabetes

The purpose of this article is to provide an overview that summarizes much in the way of our current state of knowledge regarding the pathogenesis and natural history of type 1 diabetes in humans. This information is presented to the reader as a series of seminal historical discoveries that, when advanced through research, transformed our understanding of the roles for the immune system, genes, and environment in the formation of this disease. In addition, where longitudinal investigations of these three facets occurred, their roles within the development of type 1 diabetes, from birth to symptomatic onset and beyond, are discussed, including their most controversial elements. Having an understanding of this disorder's pathogenesis and natural history is key for attempts seeking to understand the issues of what causes type 1 diabetes, as well as to develop a means to prevent and cure the disorder.

Association of cytotoxic T-lymphocyte associated antigen 4 gene polymorphism with type 1 diabetes mellitus: a meta-analysis

To evaluate the association between costimulatory molecule cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) gene polymorphism and type 1 diabetes mellitus(T1DM), sixty-three published studies before December, 2011 were included. Meta-analysis was performed for each genotype in a random/fixed effect model. The combined odds ratio (OR) with 95% confidence interval (95%CI) was calculated to estimate the strength of the association. Overall, significant correlation was noted between CTLA-4 gene polymorphism (i.e. +49A/G, CT60A/G in a per-allele model) and the risk of T1DM (for +49A/G: OR=1.47, 95%CI=1.36-1.60, P<0.001; for CT60A/G: OR=1.31, 95%CI=1.18-1.45, P<0.001). However, no significant association was noted between C(-318)T polymorphism and T1DM. In the subgroup analysis, for +49A/G and CT60A/G, the statistically significant associations were also demonstrated in diverse racial descents (Caucasian and Asian) and age of onset (<20 years and >20 years). In conclusion, our results suggest that CTLA-4 polymorphism contributes to the susceptibility of T1DM.

Harnessing memory adaptive regulatory T cells to control autoimmunity in type 1 diabetes

Type 1 diabetes (T1D) results from autoimmune destruction of insulin-producing β-cells in the pancreatic islets. There is an immediate need to restore both β-cell function and immune tolerance to control disease progression and ultimately cure T1D. Currently, there is no effective treatment strategy to restore glucose regulation in patients with T1D. FoxP3-expressing CD4(+) regulatory T cells (Tregs) are potential candidates to control autoimmunity because they play a central role in maintaining self-tolerance. However, deficiencies in either naturally occurring Tregs (nTregs) themselves and/or their ability to control pathogenic effector T cells have been associated with T1D. Here, we hypothesize that nTregs can be replaced by FoxP3(+) adaptive Tregs (aTregs), which are uniquely equipped to combat autoreactivity in T1D. Unlike nTregs, aTregs are stable and provide long-lived protection. In this review, we summarize the current understanding of aTregs and their potential for use as an immunological intervention to treat T1D.

Type 1 diabetes mellitus and components in drinking water and diet: a population-based, case-control study in Prince Edward Island, Canada

OBJECTIVE

To determine the relationship between the risk of type 1 diabetes (T1D) and daily intake of drinking water and dietary components, including nitrate, nitrite, and nitrosamines, during the year prior to diagnosis.

METHODS

Controls (n = 105) were matched by age at diagnosis and sex to T1D cases (n = 57) newly diagnosed during 2001-2004. Food consumption was assessed using a food frequency questionnaire. Locally available samples of foods were tested for nitrate, nitrite, and nitrosamine concentrations. Water consumption was determined through an additional questionnaire, and water samples were taken from homes and tested for routine chemical components, including nitrate.

RESULTS

After controlling for age, age, sex, and daily energy intake, nitrate intake from food sources showed a non-significant positive trend (odds ratios and 95% confidence intervals for quartiles = 1.00, 1.63 (0.58, 4.63), 1.71 (0.54, 5.40), 3.02 (0.78, 11.74); p for trend = 0.13). Nitrite and nitrosamine intake were not related to T1D risk (p for trend = 0.77 and 0.81, respectively). When food and water components were combined, zinc and calcium intakes were marginally and inversely related to T1D risk (p for trend = 0.07 and 0.06, respectively). After further model adjustment of possible confounders and significant risk factors, an increased intake of caffeine marginally increased the risk of T1D (p = 0.07).

CONCLUSION

Dietary components from both food and water sources may influence the risk of developing T1D in young persons.

Etiology of type 1 diabetes

Recent genetic mapping and gene-phenotype studies have revealed the genetic architecture of type 1 diabetes. At least ten genes so far can be singled out as strong causal candidates. The known functions of these genes indicate the primary etiological pathways of this disease, including HLA class II and I molecules binding to preproinsulin peptides and T cell receptors, T and B cell activation, innate pathogen-viral responses, chemokine and cytokine signaling, and T regulatory and antigen-presenting cell functions. This review considers research in the field of type 1 diabetes toward identifying disease mechanisms using genetic approaches. The expression and functions of these pathways, and, therefore, disease susceptibility, will be influenced by epigenetic and environmental factors. Certain inherited immune phenotypes will be early precursors of type 1 diabetes and could be useful in future clinical trials.

Food consumption and the risk of type 1 diabetes in children and youth: a population-based, case-control study in Prince Edward Island, Canada

OBJECTIVE

The objective of this study was to determine if the consumption of certain foods during the year prior to diagnosis of type 1 diabetes mellitus (T1D) was associated with the risk of developing T1D in children and youth residing in Prince Edward Island, Canada.

METHODS

Cases (n = 57) consisted of newly diagnosed patients with T1D during 2001 to 2004. Controls (n = 105) were randomly selected from the province's population, and matched to cases by age at diagnosis and sex. Food consumption in cases and controls was assessed using two previously validated food frequency questionnaires, and a survey was developed to collect information on potential environmental and genetic risk factors.

RESULTS

The median age at diagnosis was nine years, and 67% of cases were male. After controlling for the matched variables and four significant environmental and genetic risk factors (family members with T1D, the number of infections during the first two years of life, place of residence, and father's education) in the final logistic regression model, the consumption of regular soft drinks (OR = 2.78, 95% CI = 1.21, 6.36) and eggs (OR = 2.50, 95% CI = 1.09, 5.75) were significant risk factors of T1D, when consumed once per week or more often.

CONCLUSION

Diet may play a role in the development of T1D. However, further research is needed to confirm these observed associations.

Seasonality of month of birth differs between type 1 diabetes patients with pronounced beta-cell autoimmunity and individuals with lesser or no beta-cell autoimmunity

OBJECTIVE

To establish whether children with type 1 diabetes mellitus (T1D) with signs of pronounced beta-cell-specific autoimmunity as reflected by high autoantibody titers or positivity for several beta-cell-specific autoantibodies show a different pattern of month of birth (MOB) compared with children with T1D and low beta-cell autoimmunity and that of the general population.

RESEARCH DESIGN AND METHODS

Cosinor analysis was used to analyze MOB rhythmicity in Swedish children with new onset T1D (n = 572), in whom the glutamate decarboxylase autoantibody (GAD65Ab) titer was determined and compared with that in 833 healthy children, and in 505 children with T1D in Berlin, in whom the titers of autoantibodies to insulin, GAD65, and islet antigen-2 were compared with the MOB pattern in the general population (n = 446 571).

RESULTS

In both cohorts of children with T1D, we found that children with either a high GAD65Ab titer (above the 80th percentile) or positivity for three beta-cell-specific autoantibodies differed in their pattern of MOB from the healthy population.

CONCLUSIONS

Our past and present observations support the hypothesis that the autoimmune process leading to childhood T1D is in part triggered in the perinatal period by viral infections in genetically susceptible individuals. The present study suggests that the process is linked to titer levels of autoantibodies.

Robust associations of four new chromosome regions from genome-wide analyses of type 1 diabetes

The Wellcome Trust Case Control Consortium (WTCCC) primary genome-wide association (GWA) scan on seven diseases, including the multifactorial autoimmune disease type 1 diabetes (T1D), shows associations at P < 5 x 10(-7) between T1D and six chromosome regions: 12q24, 12q13, 16p13, 18p11, 12p13 and 4q27. Here, we attempted to validate these and six other top findings in 4,000 individuals with T1D, 5,000 controls and 2,997 family trios independent of the WTCCC study. We confirmed unequivocally the associations of 12q24, 12q13, 16p13 and 18p11 (P(follow-up) Collapse

Key Words Collapse

MESH Headings

• Adolescent
• Case-Control Studies
• Chromosome Mapping
• Diabetes Mellitus, Type 1/genetics
• Genetic Predisposition to Disease
• Genome, Human
• Humans
• Polymorphism, Single Nucleotide

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Grants

• 061859 Wellcome Trust
• 089989 Wellcome Trust
• G0000934 Medical Research Council
• Wellcome Trust
• 061858 Wellcome Trust

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Affiliation(s)

John A Todd Juvenile Diabetes Research Foundation/Wellcome Trust Diabetes and Inflammation Laboratory, Department of Medical Genetics, University of Cambridge, Addenbrooke's Hospital, Cambridge CB2 0XY, UK.
Neil M Walker
Jason D Cooper
Deborah J Smyth
Kate Downes
Vincent Plagnol
Rebecca Bailey
Sergey Nejentsev
Sarah F Field
Felicity Payne
Christopher E Lowe
Jeffrey S Szeszko
Jason P Hafler
Lauren Zeitels
Jennie H M Yang
Adrian Vella
Sarah Nutland
Helen E Stevens
Helen Schuilenburg
Gillian Coleman
Meeta Maisuria
William Meadows
Luc J Smink
Barry Healy
Oliver S Burren
Alex A C Lam
Nigel R Ovington
James Allen
Ellen Adlem
Hin-Tak Leung
Chris Wallace
Joanna M M Howson
Cristian Guja
Constantin Ionescu-Tîrgovişte
Matthew J Simmonds
Joanne M Heward
Stephen C L Gough
David B Dunger
Linda S Wicker
David G Clayton

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Identification of molecular biomarkers for multiple sclerosis

Multiple sclerosis is a demyelinating disease of the central nervous system with a presumed autoimmune etiology. Previous microarray analyses identified conserved gene expression signatures in peripheral blood mononuclear cells of patients with autoimmune diseases. We used quantitative real-time polymerase chain reaction analysis to identify a minimum number of genes of which transcript levels discriminated multiple sclerosis patients from patients with other chronic diseases and from controls. We used a computer program to search quantitative transcript levels to identify optimum ratios that distinguished among the different categories. A combination of a 4-ratio equation using expression levels of five genes segregated the multiple sclerosis cohort (n=55) from the control cohort (n=49) with a sensitivity of 91% and specificity of 98%. When autoimmune and other chronic disease groups were included (n=78), this discriminator still performed with a sensitivity of 79% and a specificity of 87%. This approach may have diagnostic utility not only for multiple sclerosis but also for other clinically complex autoimmune diseases.

Generalized multi-organ autoimmunity in CCR7-deficient mice

Development of autoimmunity is a multi-factorial process involving genetic predisposition as well as environmental and stochastic factors. Although the mechanisms responsible for the initiation of autoimmunity remain only partially understood, several studies have demonstrated that genetic predisposition plays a major role in this process. In the present study, we analyzed the influence of CCR7 signaling in the development of autoimmunity, because this chemokine receptor is essentially involved in the functional organization of thymus architecture. We demonstrate that CCR7-deficient mice are prone to develop generalized multi-organ autoimmunity. The autoimmune phenotype of CCR7-/- mice encompasses the presence of lymphocyte infiltrates in several peripheral organs, circulating autoantibodies against a multitude of tissue-specific antigens and IgG deposition on renal glomeruli. Additionally, CCR7-deficient mice show increased susceptibility to streptozotocin-induced diabetes and spontaneously display signs of chronic autoimmune renal disease. Thus, this study identifies CCR7 as a genetic factor involved in the regulation of autoimmunity.

A type 1 diabetes subgroup with a female bias is characterised by failure in tolerance to thyroid peroxidase at an early age and a strong association with the cytotoxic T-lymphocyte-associated antigen-4 gene

AIMS/HYPOTHESIS

HLA haplotypes DRB1*03_DQB1*02 and DRB1*04_DQB1*0302, and allelic variation of the T cell regulatory gene cytotoxic T-lymphocyte-associated antigen-4 (CTLA4) and of the T cell activation gene protein tyrosine phosphatase, non-receptor type 22 (lymphoid) (PTPN22) have been associated with type 1 diabetes and autoimmune thyroid disease. Using thyroid peroxidase autoantibodies (TPOAbs) as an indicator of thyroid autoimmunity, we assessed whether the association of these loci is different in type 1 diabetes patients with TPOAbs than in those without.

MATERIALS AND METHODS

TPOAbs were measured in 4,364 type 1 diabetic patients from across Great Britain, 67% of whom were aged under 18 years. These patients and 6,866 geographically matched control subjects were genotyped at CTLA4, PTPN22, HLA-DRB1 and HLA-DQB1.

RESULTS

TPOAbs were detected in 462 (10.6%) of the type 1 diabetic patients. These patients had a stronger association with CTLA4 (odds ratio [OR] = 1.49 for the G allele of the single nucleotide polymorphism rs3087243; 95% CI = 1.29-1.72) than did the TPOAbs-negative patients (p = 0.0004; OR = 1.16; 95% CI = 1.10-1.24) or type 1 diabetes patients overall (OR = 1.20; 95% CI = 1.13-1.27). The ratio of women:men was higher (1.94:1) in this subgroup than in type 1 diabetes patients without TPOAbs (0.94:1; p = 1.86 x 10(-15)). TPOAbs status did not correlate with age at diagnosis of type 1 diabetes or with PTPN22 (Arg620Trp; rs2476601).

CONCLUSIONS/INTERPRETATION

Our results identify a subgroup of type 1 diabetic patients that is sensitive to allelic variation of the negative regulatory molecule CTLA-4 and indicate that TPOAbs testing could be used to subclassify type 1 diabetes patients for inclusion in genetic, biological or clinical studies.

Deregulated stress system in non-obese diabetic lymphocyte

Lymphopenia-induced homeostatic expansion in non-obese diabetic (NOD) mice may lead to autoimmunity. We demonstrated that NOD lymphocytes are more susceptible to apoptosis than those of non-diabetic C57BL/6 or NOD.H2(h4) mice in vivo and in vitro, which may be an underlying mechanism causing lymphopenia in NOD mice. Gene expression profiling identified a set of genes that are differentially expressed between NOD and B6 mice. Identity of these genes suggested that NOD T cells have a deregulated stress response system, especially heat-shock protein family, making them overly sensitive to apoptosis. Thus, we hypothesize that this strain-specific gene expression profile may confer a liability upon NOD T cells making them more susceptible to apoptosis that may lead to lymphopenia in NOD mice and contribute to development of autoimmunity.

Identification of gene expression signatures in autoimmune disease without the influence of familial resemblance

Even though autoimmune diseases are heterogeneous, believed to result from the interaction between genetic and environmental components, patients with these disorders exhibit reproducible patterns of gene expression in their peripheral blood mononuclear cells. A portion of this gene expression profile is a property of familial resemblance rather than autoimmune disease. Here, we wanted to identify the portion of this gene expression profile that is independent of familial resemblance and determine whether it is a product of disease duration, disease onset or other factors. By employing supervised clustering algorithms, we identified 100 genes whose expression profiles are shared in individuals with various autoimmune diseases but are not shared by unaffected family members of individuals with autoimmune disease or by controls. Individuals with early disease (1 year after onset) and established disease (10 years after onset) exhibit a near-identical expression pattern, suggesting that this unique profile is a product of disease onset rather than disease duration.

Type 1 diabetes mellitus: etiology, presentation, and management

This article reviews our current understanding of the etiology, presentation, and management of type 1 diabetes. The discussion includes a review of the natural history of diabetes, the complex relationship between genetic and environmental risk for type 1 diabetes, and current methods for prediction of type 1 diabetes. The article also reviews the current management of children who have new-onset type 1 diabetes, age-appropriate management goals, and diabetes complications. Finally, the article discusses the future of diabetes screening programs and the progress toward the ultimate goal of curing type 1 diabetes.

Comparison of differentially expressed genes in T lymphocytes between human autoimmune disease and murine models of autoimmune disease

A general view is that critical genes involved in biological pathways are highly conserved among species. To understand human autoimmune diseases, a great deal of effort has been devoted to the study of murine models that mirror many pathologic properties observed in the human disease. We have found that lymphocytes from humans with different autoimmune disease all carry a common conserved gene expression profile. Therefore, we wanted to determine if lymphocytes from common murine models of autoimmune disease carried a gene expression profile similar to the human profile and if both mouse models carried a shared gene expression profile. We identified numerous differentially expressed genes (DEGs) in the autoimmune strains compared to non-autoimmune strains. However, we found very little overlap in the gene expression profile between human autoimmune disease and murine models of autoimmune disease and between different murine autoimmune models. Our research further confirms that murine models of autoimmunity do not perfectly match human autoimmune diseases.

Terminal deoxynucleotidyltransferase deficiency decreases autoimmune disease in diabetes-prone nonobese diabetic mice and lupus-prone MRL-Fas(lpr) mice

The wide diversity of the T and B Ag receptor repertoires becomes even more extensive postneonatally due to the activity of TdT, which adds nontemplated N nucleotides to Ig and TCR coding ends during V(D)J recombination. In addition, complementarity-determining region 3 sequences formed in the absence of TdT are more uniform due to the use of short sequence homologies between the V, D, and J genes. Thus, the action of TdT produces an adult repertoire that is both different from, and much larger than, the repertoire of the neonate. We have generated TdT-deficient nonobese diabetic (NOD) and MRL-Fas(lpr) mice, and observed a decrease in the incidence of autoimmune disease, including absence of diabetes and decreased pancreatic infiltration in NOD TdT(-/-) mice, and reduced glomerulonephritis and increased life span in MRL-Fas(lpr) TdT(-/-) mice. Using tetramer staining, TdT(-/-) and TdT(+/+) NOD mice showed similar frequencies of the diabetogenic BDC 2.5 CD4(+) T cells. We found no increase in CD4(+)CD25(+) regulatory T cells in NOD TdT(-/-) mice. Thus, TdT deficiency ameliorates the severity of disease in both lupus and diabetes, two very disparate autoimmune diseases that affect different organs, with damage conducted by different effector cell types. The neonatal repertoire appears to be deficient in autoreactive T and/or B cells with high enough affinities to induce end-stage disease. We suggest that the paucity of autoreactive specificities created in the N region-lacking repertoire, and the resultant protection afforded to the newborn, may be the reason that TdT expression is delayed in ontogeny.

Testing the possible negative association of type 1 diabetes and atopic disease by analysis of the interleukin 4 receptor gene

Variations in the interleukin 4 receptor A (IL4RA) gene have been reported to be associated with atopy, asthma, and allergy, which may occur less frequently in subjects with type 1 diabetes (T1D). Since atopy shows a humoral immune reactivity pattern, and T1D results from a cellular (T lymphocyte) response, we hypothesised that alleles predisposing to atopy could be protective for T1D and transmitted less often than the expected 50% from heterozygous parents to offspring with T1D. We genotyped seven exonic single nucleotide polymorphisms (SNPs) and the -3223 C>T SNP in the putative promoter region of IL4RA in up to 3475 T1D families, including 1244 Finnish T1D families. Only the -3223 C>T SNP showed evidence of negative association (P=0.014). There was some evidence for an interaction between -3233 C>T and the T1D locus IDDM2 in the insulin gene region (P=0.001 in the combined and P=0.02 in the Finnish data set). We, therefore, cannot rule out a genetic effect of IL4RA in T1D, but it is not a major one.

An increasing trend in the incidence of type 1 diabetes mellitus in children aged 0-14 years in Romania--ten years (1988-1997) EURODIAB study experience

AIM

To assess the incidence of type 1 diabetes mellitus (DM1) in Romanian children aged 0-14 years using EURODIAB Study methodology.

METHODS

Data were collected for a 10-year interval (1988-1997) for the whole country, using the capture-recapture method.

RESULTS

We registered 1,418 newly diagnosed patients. The mean total incidence rate was 3.051/100,000/year. There was a wide geographic variation (6.71-fold) between the highest and the lowest incidence rates in different districts. We noticed a progressive increase of age-specific incidence rates from 1.43/100,000/year for the 0-4 year age subgroup to 4.37/100,000/year (10-14 years). The annual mean incidence rate rose from 1.91/100,000/year (1988) to 3.94/100,000/year (1996).

CONCLUSIONS

Romania is one of the European countries with the lowest incidence rates (3.051/100,000/year) for DM1 in children. There was an evident increasing trend of DM1 incidence in children between 1988 and 1997, with an annual increase of 7.57%.

Type 1 diabetes genetic susceptibility encoded by HLA DQB1 genes in Romania

Most cases of type 1 diabetes (T1DM) are due to an immune-mediated destruction of the pancreatic beta cells, a process that is conditioned by multiple genes and environmental factors. The main susceptibility genes are represented by the class II HLA-DRB1 and DQB1 alleles. The aim of our study was to reconfirm the contribution of HLA-DQB1 polymorphisms to T1DM genetic susceptibility for the Romanian population. For this, 219 Romanian T1DM families were genotyped at high resolution for HLA DQB1 using the PCR-SSOP method (Polymerase Chain Reaction - Sequence Specific Oligonucleotide Probes). Allele transmission to diabetics and unaffected siblings was studied using the Transmission Disequilibrium Test (TDT). We found an increased transmission of DQB1*02 (77.94% transmission, p(TDT) = 7.18 x 10(-11)) and DQB1*0302 (80.95% transmission, p(TDT) = 2.25 x 10(-10)) alleles to diabetics, indicating the diabetogenic effect of these alleles. Conversely, DQB1*0301, DQB1*0603, DQB1*0602, DQB1*0601 and DQB1*05 alleles are protective, being significantly less transmitted to diabetics. In conclusion, our results confirmed the strong effect of HLA-DQB1 alleles on diabetes risk in Romania, with some characteristics which can contribute to the low incidence of T1DM in this country.

Enteroviruses and type 1 diabetes mellitus

Despite decades of research, the etiology of type 1 diabetes mellitus (DM) is unknown. Several risk factors have been associated with type 1 DM, including viral infections, genetic predisposition, nutritional factors, and chemicals. Several investigators hypothesize that the etiologies of type 1 DM result from a complex interaction of genetic and environmental factors. In this paper we review the epidemiologic data linking enteroviruses to type 1 DM and discuss potential mechanisms of pathogenesis.

Mapping multiple sclerosis susceptibility to the HLA-DR locus in African Americans

An underlying complex genetic susceptibility exists in multiple sclerosis (MS), and an association with the HLA-DRB1*1501-DQB1*0602 haplotype has been repeatedly demonstrated in high-risk (northern European) populations. It is unknown whether the effect is explained by the HLA-DRB1 or the HLA-DQB1 gene within the susceptibility haplotype, which are in strong linkage disequilibrium (LD). African populations are characterized by greater haplotypic diversity and distinct patterns of LD compared with northern Europeans. To better localize the HLA gene responsible for MS susceptibility, case-control and family-based association studies were performed for DRB1 and DQB1 loci in a large and well-characterized African American data set. A selective association with HLA-DRB1*15 was revealed, indicating a primary role for the DRB1 locus in MS independent of DQB1*0602. This finding is unlikely to be solely explained by admixture, since a substantial proportion of the susceptibility chromosomes from African American patients with MS displayed haplotypes consistent with an African origin.

Causality or coincidence: may the slow disappearance of helminths be responsible for the imbalances in immune control mechanisms?

Intestinal infection continues to be a problem worldwide and helminths, which currently infect billions of individuals, are primary culprits. The major burden of disease falls on the populations of developing countries, given that over the last four to five decades helminth infections are disappearing in industrialized societies. In developing countries, a major source of immunomodulatory signals in post-natal life are parasites, particularly helminths, which, unlike most bacteria and viruses, selectively stimulate Th2 function. Helminths and their eggs are probably the most potent stimulators of mucosal Th2 responses. Responses elicited by worms can modulate immune reactions to other parasites, bacterial, viral infections and several unrelated diseases. Bacterial and protozoal infections may also protect against atopy and asthma, through the induction of the Th1 regulatory responses. Today, people in developed countries often live in ultra-hygienic environments, avoiding exposure to viruses, bacteria, ectoparasites and endoparasites, particularly helminths. Perhaps failure to acquire worms and experience mucosal Th2 conditioning predisposes to unrelated diseases. In contrast to this hypothesis it has also been suggested that Th2 responses can make the host more susceptible to other important diseases and to contribute to the spread of them.

Association of the T-cell regulatory gene CTLA4 with susceptibility to autoimmune disease

Genes and mechanisms involved in common complex diseases, such as the autoimmune disorders that affect approximately 5% of the population, remain obscure. Here we identify polymorphisms of the cytotoxic T lymphocyte antigen 4 gene (CTLA4)--which encodes a vital negative regulatory molecule of the immune system--as candidates for primary determinants of risk of the common autoimmune disorders Graves' disease, autoimmune hypothyroidism and type 1 diabetes. In humans, disease susceptibility was mapped to a non-coding 6.1 kb 3' region of CTLA4, the common allelic variation of which was correlated with lower messenger RNA levels of the soluble alternative splice form of CTLA4. In the mouse model of type 1 diabetes, susceptibility was also associated with variation in CTLA-4 gene splicing with reduced production of a splice form encoding a molecule lacking the CD80/CD86 ligand-binding domain. Genetic mapping of variants conferring a small disease risk can identify pathways in complex disorders, as exemplified by our discovery of inherited, quantitative alterations of CTLA4 contributing to autoimmune tissue destruction.

A major role for non-major histocompatibility complex genes but not for microorganisms in a novel murine model of Graves' hyperthyroidism

The etiology of Graves' disease is multifactorial. We investigated the role of genetic and environmental factors on the susceptibility to Graves' hyperthyroidism using a new murine model. Intramuscular injection of recombinant adenovirus expressing the thyrotropin receptor (AdCMVTSHR) induces Graves'-like hyperthyroidism (thyrotropin receptor [TSHR] antibodies, elevated thyroxine, and diffuse goiter) in more than 50% of female BALB/c mice. The relative contributions of major histocompatibility complex (MHC) and non-MHC genes on the susceptibility to hyperthyroidism were studied by immunizing BALB/c (H-2d), BALB.K (H-2k), and DBA/2J (H-2d) mice with AdCMVTSHR. Hyperthyroidism developed in approximately 50% of BALB/c and BALB.K mice but only 5% of DBA/2J mice, indicating a major role for non-MHC genes in disease development. The effect of environmental microorganisms was evaluated by comparing disease incidence in BALB/c mice maintained in pathogen-free conditions versus those in nonsterile, conventional housing, as well as by coadministering microorganism components (Escherichia coli lipopolysaccharide or yeast zymosan A) as adjuvants with AdCMVTSHR. Neither type of exposure to environmental pathogens influenced disease induction. In conclusion, non-MHC genes, but not infectious organisms, play a major role in the etiology of this novel murine model of Graves' disease.

The rise of childhood type 1 diabetes in the 20th century

The incidence of childhood type 1 diabetes increased worldwide in the closing decades of the 20th century, but the origins of this increase are poorly documented. A search through the early literature revealed a number of useful but neglected sources, particularly in Scandinavia. While these do not meet the exacting standards of more recent surveys, tentative conclusions can be drawn concerning long-term changes in the demography of the disease. Childhood type 1 diabetes was rare but well recognized before the introduction of insulin. Low incidence and prevalence rates were recorded in several countries over the period 1920-1950, and one carefully performed study showed no change in childhood incidence over the period 1925-1955. An almost simultaneous upturn was documented in several countries around the mid-century. The overall pattern since then is one of linear increase, with evidence of a plateau in some high-incidence populations and of a catch-up phenomenon in some low-incidence areas. Steep rises in the age-group under 5 years have been recorded recently. The disease process underlying type 1 diabetes has changed over time and continues to evolve. Understanding why and how this produced the pandemic of childhood diabetes would be an important step toward reversing it.

The study of CTLA-4 and vitamin D receptor polymorphisms in the Romanian type 1 diabetes population

Several studies suggested that part of the genetic susceptibility for Type 1 diabetes (T1DM) is encoded by some polymorphisms of CTLA-4 gene (2q33) and of Vitamin D Receptor gene (VDR; 12q12-14). Our aim was to assess their contribution to T1DM genetic susceptibility in the Romanian population. We typed CTLA-4 49 A/G and VDR FokI (F/f), ApaI (A/a) and TaqI (T/t) polymorphisms by Sequence Specific Primer PCR (SSP-PCR) in 204 Romanian diabetic families (756 individuals: 212 T1DM probands and 544 unaffected parents and siblings). We studied alleles transmission using the Transmission Disequilibrium Test (TDT). We found an increased transmission of CTLA-4 49G allele to diabetics (54.8%, p=0.11). The transmission of F (56.1%, p=0.063), a (55.7%, p=0.061) and T (51.8%, p=0.37) alleles of VDR gene to diabetics was increased but did not reach statistical significance. In conclusion we found the same increased transmission of CTLA-4 49 G allele to diabetics as previously reported. VDR FoqI F allele seems to be predisposing while TaqI T allele seems to be protective.

Antibodies to food antigens in Japanese patients with type 1 diabetes mellitus

To examine humoral and mucosal immune responses to food antigens and their relation to the pathophysiology of type 1 diabetes mellitus, IgA and IgG antibodies to cow's milk antigens (bovine serum albumin (BSA) and beta-lactoglobulin (BLG)) and another food antigen (ovalbumin, (OVA)) in human serum were assessed by enzyme-linked immunosorbent assay (ELISA). If anti-idiotype antibodies to the antibodies were present in serum, they might interfere with the ELISA assay, so suitable microtiter plates were employed to minimize such interference. The levels of IgA and IgG antibodies to the above antigens (P<0.001-P<0.01) and the prevalence of positive sera (P<0.001-P<0.05) in the patient group (n=52, aged 14.5+/-4.1 (S.D.) years) were significantly higher than those in the control group (n=41, aged 13.3+/-6.8 (S.D.) years). Interestingly, the levels of IgA antibodies to all the food antigens examined were elevated in 26 (50%) patients, while the elevation was seen in 3 (7%) healthy controls. The elevation of IgA antibodies in the patients was well correlated with increased concentrations of IgA and transforming growth factor (TGF)-beta, which induces IgA-producing B-cells, in serum. Although the cytokine TGF-beta is secreted from regulatory T-cells (Th3), and is related to oral tolerance, the interleukin-2 (IL-2, Th1)/IL-4 (Th2) ratio in the patient group was significantly elevated (P<0.001), which might indicate that the oral tolerance is impaired in patients. Thus, we demonstrated that both IgA and IgG antibodies to several food antigens are elevated in patients. We suggest that impairment of oral tolerance might be related to the pathogenesis of type 1 diabetes mellitus.

The genetics of complex autoimmune diseases: non-MHC susceptibility genes

Susceptibility to complex autoimmune diseases (AIDs) is a multigenic phenotype affected by a variety of genetic and environmental or stochastic factors. After over a decade of linkage analyses, the identification of non-major histocompatibility complex (non-MHC) susceptibility alleles has proved to be difficult, predominantly because of extensive genetic heterogeneity and possible epistatic interactions among the multiple genes required for disease development. Despite these difficulties, progress has been made in elucidating the genetic mechanisms that influence the inheritance of susceptibility, and the pace of gene discovery is accelerating. An intriguing new finding has been the colocalization of several AID susceptibility genes in both rodent models and human linkage studies. This may indicate that several susceptibility alleles affect multiple AIDs, or alternatively that genomic organization has resulted in the clustering of many immune system genes. The completion of the human genome sequence, coupled with the imminent completion of the mouse genome, should yield key information that will dramatically enhance the rate of gene discovery in complex conditions such as AID susceptibility.

Genetic protection from the inflammatory disease type 1 diabetes in humans and animal models

Populations of humans and mice contain alleles at many loci that protect from immune-mediated diseases. Identification of these alleles, some which are likely to function in immune recognition, tolerance, and regulation, will facilitate the development of diagnostics as well as therapeutics that alter disease progression.

The effect of day care exposure on the risk of developing type 1 diabetes: a meta-analysis of case-control studies

OBJECTIVE

Exposure to infections in infancy or childhood may be important in the pathogenesis of type 1 diabetes, but a protective role has also been suggested. We tested the hypothesis that increased early contact with infectious agents, measured by day care exposure, would decrease the risk of type 1 diabetes in childhood.

RESEARCH DESIGN AND METHODS

We conducted a systematic review of case-control studies. Meta-analysis was performed to combine results, assess for heterogeneity, and explore variation in study design.

RESULTS

Several generally well-designed case-control studies show a statistically significant protective effect of day care on type 1 diabetes. However, meta-analysis revealed too much heterogeneity to accept the overall synthesis results and none of the studies used prerecorded data. Day care does seem to have a protective effect in the subgroup of children who will be diagnosed with type 1 diabetes before the age of 5 years (odds ratio = 0.6, 95% CI 0.5-0.8); however, this result is based on only two studies.

CONCLUSIONS

Recall bias is one alternate explanation for these data; confirmation using prerecorded data is required. Such data could be prospectively measured in cohort studies of children at risk. We also suggest that information about day care attendance be measured in randomized trials of agents for the prevention of type 1 diabetes, as day care exposure could potentially modify the effect of the preventive agent.

Complex trait analysis in the mouse: The strengths, the limitations and the promise yet to come

In 1990, David Baltimore predicted that the 1990s would be the decade of the mouse (). This certainly proved to be true: The mouse has contributed immensely to biological research through transgenic, embryonic stem cell (ES) knockout, and classical genetic technologies. But its usefulness as a model organism is by no means over; indeed it is still rising to its peak: The mouse as a model mammalian organism still has much to offer. This article reviews use of the mouse to dissect complex genetic traits using quantitative trait analysis, with a particular emphasis on medically important diseases.

Application and interpretation of transmission/disequilibrium tests: transmission of HLA-DQ haplotypes to unaffected siblings in 526 families with type 1 diabetes

It is widely believed that, if a genetic marker shows a transmission distortion in patients by the transmission/disequilibrium test (TDT), then a transmission distortion in healthy siblings would be seen in the opposite direction. This is also the case in a complex disease. Furthermore, it has been suggested that replacing the McNemar statistics of the TDT with a test of heterogeneity between transmissions to affected and unaffected children could increase the power to detect disease association. To test these two hypotheses empirically, we analyzed the transmission of HLA-DQA1-DQB1 haplotypes in 526 Norwegian families with type 1 diabetic children and healthy siblings, since some DQA1-DQB1 haplotypes represent major genetic risk factors for type 1 diabetes. Despite the strong positive and negative disease associations with particular DQ haplotypes, we observed no significant deviation from 50% for transmission to healthy siblings. This could be explained by the low penetrance of susceptibility alleles, together with the fact that IDDM loci also harbor strongly protective alleles that can override the risk contributed by other loci. Our results suggest that, in genetically complex diseases, detectable distortion in transmission to healthy siblings should not be expected. Furthermore, the original TDT seems more powerful than a heterogeneity test.

Childhood Type 1 diabetes mellitus and parental occupations involving social mixing and infectious contacts: two population-based case-control studies

AIMS

To test the hypothesis that increased exposure to infections, through parental jobs involving high levels of social mixing, reduces the risk of childhood Type 1 diabetes mellitus.

METHODS

Two population-based case-control studies of children diagnosed with Type 1 diabetes mellitus from Yorkshire (0-15 years) and Northern Ireland (0-14 years) included 220 and 189 cases and 433 and 465 controls, respectively. Parental occupations were coded using a standard occupational classification. Each job was allocated to high, medium or low levels of social mixing according to a predefined categorization. Odds ratios (OR) for the risk of childhood Type 1 diabetes were estimated for parental social mixing by age at diagnosis.

RESULTS

Childhood Type 1 diabetes mellitus was not associated with high levels of parental occupational social mixing (Yorkshire - mothers: OR 1.07, 95% confidence interval (CI) 0.76-1.50; fathers: 1.15, 0.75-1.76; Northern Ireland - heads of household, usually the father: 0.78, 0.49-1.25). A larger proportion of mothers (39%) compared to fathers (18% Yorkshire, 17% Northern Ireland) had jobs involving high levels of social mixing. Mothers with high social mixing jobs conferred a nonsignificant reduced risk of Type 1 diabetes among children diagnosed under 5 years of age (0.58, 0.24-1.38) compared to those diagnosed at age 5 years and above (1.14, 0.77-1.69).

CONCLUSIONS

No association between parental occupational social mixing and the risk of childhood Type 1 diabetes mellitus was detected for all ages combined. Mothers were more likely to have jobs involving high levels of social mixing than fathers. The possible protective effect of maternal high occupational social mixing on children diagnosed below 5 years of age merits further investigation.

Month of birth and subsequent development of type I diabetes (IDDM)

The aim of this study was to find out whether there is a seasonal pattern in the month of birth of children with IDDM in Israel and whether this pattern, if present, differs from that of total live births. One thousand and ninety-five out of 1,188 children and adolescents (0-17 years) who developed IDDM in Israel between 1980-1993 and whose month of birth was known were included in the study. Separate analysis was made for Jews (n = 987) who have a high incidence (10-18/105) and Arabs (n = 108) with a low incidence (2.9/105) of IDDM. The pattern of total live birth distribution in Israel over a 20-year period served as control. A significantly different seasonal pattern was found in the two IDDM populations. Whereas the Jews had the lowest number of births in winter (January-March) and the highest in spring (April-June), the Arabs presented an inverse pattern in the first months of the year. The distribution of births of the children who developed IDDM was different from that observed in total live births in the Jewish population. The findings in the Jewish population in Israel (a high incidence group) support the hypothesis that IDDM is triggered in some children by viral infections transmitted by the mother during pregnancy or in the early postnatal period. In the Arab population (a low incidence group) a protective (immune and/or genetic) mechanism may exist.

The predisposition to type 1 diabetes linked to the human leukocyte antigen complex includes at least one non-class II gene

The human leukocyte antigen (HLA) complex, encompassing 3.5 Mb of DNA from the centromeric HLA-DPB2 locus to the telomeric HLA-F locus on chromosome 6p21, encodes a major part of the genetic predisposition to develop type 1 diabetes, designated "IDDM1." A primary role for allelic variation of the class II HLA-DRB1, HLA-DQA1, and HLA-DQB1 loci has been established. However, studies of animals and humans have indicated that other, unmapped, major histocompatibility complex (MHC)-linked genes are participating in IDDM1. The strong linkage disequilibrium between genes in this complex makes mapping a difficult task. In the present paper, we report on the approach we have devised to circumvent the confounding effects of disequilibrium between class II alleles and alleles at other MHC loci. We have scanned 12 Mb of the MHC and flanking chromosome regions with microsatellite polymorphisms and analyzed the transmission of these marker alleles to diabetic probands from parents who were homozygous for the alleles of the HLA-DRB1, HLA-DQA1, and HLA-DQB1 genes. Our analysis, using three independent family sets, suggests the presence of an additional type I diabetes gene (or genes). This approach is useful for the analysis of other loci linked to common diseases, to verify if a candidate polymorphism can explain all of the association of a region or if the association is due to two or more loci in linkage disequilibrium with each other.

From genome to aetiology in a multifactorial disease, type 1 diabetes

The common autoimmune disease type 1 diabetes provides a paradigm for the genetic analysis of multifactorial disease. Disease occurrence is attributable to the interaction with the environment of alleles at many loci interspersed throughout the genome. Their mapping and identification is difficult because the disease-associated alleles occur almost as commonly in patients as in healthy individuals; even the highest-risk genotypes bestow only modest risks of disease. The identification of common quantitative trait loci (QTL) in autoimmune disease and in other common disorders, therefore, requires a very close marriage of genetics and biology. Two QTLs have been identified in human type 1 diabetes: the major histocompatibility complex HLA class II loci and a promoter polymorphism of the insulin gene. The evidence for their primary roles in disease aetiology demonstrates the necessity of combined studies of genetics and biology. Their functions and interaction underpin an emerging picture of the basic causes of the disease and direct analyses towards other candidate genes and pathways. The genetic tools used for QTL identification include transgenesis and gene knockouts, whole genome scanning for linkage, mouse congenic strains, linkage disequilibrium mapping, and the establishment of ancestral haplotypes among disease-associated chromosomes.

TCR-Vbeta usage in the thymus and blood of myasthenia gravis patients

In myasthenia gravis (MG) the muscle acetylcholine receptor (AChR) is the target of an autoimmune response. The anti-AChR response may originate in the thymus, which is abnormal in most MG patients and contains anti-AChR T and B cells. Microbial superantigens (sAg) may trigger autoimmune responses and in this study we sought clues as to whether sAg play a role in the pathogenesis of MG. We investigated the frequency of use of the different TCR Vbeta families by the thymus and blood T cells in MG patients and in control subjects, using a multi-primer PCR assay. Identical TCR-Vbeta usage was found in the thymi of MG patients and controls, except Vbeta2, which showed a small increase in MG patients' thymi. Blood T cells of MG patients used Vbeta4, Vbeta6, Vbeta15, Vbeta16 and Vbeta24 significantly more than those of the controls. Vbeta4 and Vbeta6 are the gene families most frequently used by anti-AChR CD4(+) cells in MG patients. Blood T cells from MG patients used Vbeta12, Vbeta14, Vbeta17 and Vbeta18 significantly less than controls. MG patients used Vbeta4 and Vbeta6 significantly more in the blood than in the thymus, while the opposite occurred for Vbeta7, Vbeta12 and Vbeta14. Controls used Vbeta17 more and Vbeta24 less in the blood than in the thymus. The preferential expansion of Vbeta4 and Vbeta6 in MG patients might reflect the immunodominance of certain AChR epitopes, or the action of a sAg outside the thymus. The minimal differences in the TCR-Vbeta usage in the blood and thymus of control subjects might be due to expansion of T cell clones specific for common antigens. Identical Vbeta usage in the thymi of MG patients and controls does not support an important role of the thymus as the location of anti-AChR sensitization when MG is clinically evident. The differences observed in the Vbeta usage in blood and thymi of MG patients are likely to be due to preferential Vbeta usage by the anti-AChR T cells in the blood.

Human type 1 diabetes and the insulin gene: principles of mapping polygenes

We review the strategy used to identify a susceptibility locus (IDDM2) for type 1 (insulin dependent) diabetes mellitus. As type 1 diabetes is becoming the paradigm for dissecting multifactorial disease genetics, the approach described provides important general guidelines for positional cloning of human disease polygenes. Main topics include: (a) historical conspectus of the mapping and identification of IDDM2--a critical survey of the work leading up to the conclusion that IDDM2 most likely corresponds to allelic variation at the insulin gene minisatellite (VNTR) locus; (b) the nature of allelic (length and sequence) variation at the VNTR locus; (c) gene interactions and disease pathogenesis; (d) mechanism of action of the INS VNTR in type 1 diabetes--insulin gene expression, parent-of-origin effects (genomic imprinting); and (e) summary and future prospects--alleles of the insulin VNTR that are protective for type 1 diabetes appear to encode susceptibility to type 2 diabetes.

Panning for gold: genome-wide scanning for linkage in type 1 diabetes

Genome-wide scans for linkage of chromosome regions to type 1 diabetes in affected sib pair families have revealed that the major susceptibility locus resides within the major histocompatibility complex (MHC) on chromosome 6p21 (lambda S = 2.4). It is recognized that the MHC contains multiple susceptibility loci (referred to collectively as IDDM1), including the class II antigen receptor genes, which control the major pathological feature of the disease: T-lymphocyte-mediated autoimmune destruction of the insulin-producing pancreatic beta cells. However, the MHC genes, and a second locus, the insulin gene minisatellite on chromosome 11p15 (IDDM2; lambda S = 1.25), cannot account for all of the observed clustering of disease in families (lambda S = 15), and the scans suggested the presence of other susceptibility loci scattered throughout the genome. There are four additional loci for which there is currently sufficient evidence from linkage and association studies to justify fine mapping experiments: IDDM4 (FGF3/11q13), IDDM5 (ESR/6q22), IDDM8 (D6S281/6q27) and IDDM12 (CTLA-4/2q33). IDDM4, 5 and 8 were detected by genome scanning, and IDDM12 by a candidate gene strategy. Seven other named loci are not discounted but remain to be replicated widely. Multiple susceptibility loci were expected as genome-wide scans of the mouse model of type 1 diabetes had shown that although the MHC is the major mouse locus, at least 13 genes unlinked to the MHC are involved in the development of disease. Genome-wide scans using 1000 affected sibpair families will be required to be confident that all genes with effects on familial clustering equivalent to the insulin gene locus (lambda S = 1.25) have been detected. The identification of aetiological determinants requires exclusion of hitchhiking polymorphisms in regions of linkage disequilibrium, as demonstrated for the MHC and the insulin gene loci, and functional studies implicating the disease-associated variant in pathogenesis. Ultimately, targeting of specific candidate mutations in mice by homologous recombination and replacement will be necessary to prove the primary role of any candidate mutation.

No primary association between the 308 polymorphism in the tumor necrosis factor alpha promoter region and insulin-dependent diabetes mellitus

Whereas TNF-alpha has been implicated in the pathogenesis of IDDM, its possible role as a primary genetic susceptibility factor has not been well investigated. In this study, we analyzed a biallelic polymorphism in the TNF-alpha promotor region in a large collection of IDDM patients and controls ascertained from two ethnic populations (U.S. Caucasians and Chinese in Taiwan). We report that the associations with TNF-alpha are due to linkage disequilibrium between TNF-alpha and the DR3-DQB1*0201 haplotype in both ethnic populations. Our analyses of extended haplotypes for the HLA region further substantiate the conclusion that no primary association exists between IDDM and the TNF-alpha promoter polymorphism.

HLA-encoded susceptibility to insulin-dependent diabetes mellitus is determined by DR and DQ genes as well as their linkage disequilibria in a Chinese population

HLA-DRB1 and -DQB1 genes were analyzed in 98 Chinese IDDM patients and 205 control subjects from Taiwan. The DRB1*0301-DQB1*0201 haplotype conferred strong susceptibility (RR = 7.7, pc < 10(-5)). DRB1*0405 also conferred susceptibility (RR = 3.1, Pc < 0.0005) whereas DRB1*0403 (RR = 0.7) and DRB1*0406 (RR = 0.2) conferred protection. Indeed, the relative risk for the DRB1*0405-DQB1*0302 haplotype (RR = 33.7, Pc < 0.002) was 48 and 168 times higher than those conferred by the DRB1*0403-DQB1*0302 and DRB1*0406-DQB1*0302 haplotypes, respectively, suggesting that the protection conferred by DRB1*0403 and 0406 is dominant over DQB1*0302. The strong linkage disequilibrium observed between DQB1*0302 and DRB1*0403(0406) can thus explain the surprising finding that the frequency of DQB1*0302 was not significantly increased in the Chinese IDDM patients (RR = 0.9). Because the DRB1*0405-DQB1*0302 haplotype (RR = 33.7) conferred higher susceptibility than the DRB1*0405-DQB1*0401 (RR = 2.5) or DRB1*0405-DQB1*0301 (RR = 2.1) haplotypes, DQB1*0302 is indeed a susceptibility factor, while both DQB1*0301 and DQB1*0401 may confer protection against IDDM. The increased frequency of the protective DQB1*0401 allele in patients compared to controls is due to linkage disequilibrium between DRB1*0405 and DQB1*0401. Interestingly, the previously demonstrated protective effect of DQB1*0602 was not very strong in the Chinese (RR = 0.4). Our results suggested that HLA-encoded susceptibility to IDDM is determined by the combined effects of all DR and DQ molecules present in an individual. Therefore, the genotypic combinations of DR and DQ genes as well as their linkage disequilibria can influence IDDM susceptibility. At least four DR and DQ molecules conferring high susceptibility (DRB1*0301, DRB1*0405, and DQ alpha/beta 0301/0201 and 0301/0302) occur at high frequency in the Chinese population. However, linkage disequilibria between highly susceptible DR and protective DQ or vice versa (e.g., DRB1*0405-DQB1*0301[0401] and DRB1*0403[0406]-DQB1*0302) are probably responsible for the lower incidence of IDDM in the Chinese.

Genetic analysis of type 1 diabetes using whole genome approaches

Whole genome linkage analysis of type 1 diabetes using affected sib pair families and semi-automated genotyping and data capture procedures has shown how type 1 diabetes is inherited. A major proportion of clustering of the disease in families can be accounted for by sharing of alleles at susceptibility loci in the major histocompatibility complex on chromosome 6 (IDDM1) and at a minimum of 11 other loci on nine chromosomes. Primary etiological components of IDDM1, the HLA-DQB1 and -DRB1 class II immune response genes, and of IDDM2, the minisatellite repeat sequence in the 5' regulatory region of the insulin gene on chromosome 11p15, have been identified. Identification of the other loci will involve linkage disequilibrium mapping and sequencing of candidate genes in regions of linkage.

Trichloroethylene--a review of the literature from a health effects perspective

This report reviews the literature on the impact of exposure to trichloroethylene (TCE) on human health. Special emphasis is given to the health effects reported in excess of national norms by participants in the TCE Subregistry of the Volatile Organic Compounds Registry of the National Exposure Registries--persons with documented exposure to TCE through drinking and use of contaminated water. The health effects reported in excess by some or all of the sex and age groups studied were speech and hearing impairments, effects of stroke, liver problems, anemia and other blood disorders, diabetes, kidney disease, urinary tract disorders, and skin rashes.

Insulin gene region-encoded susceptibility to type 1 diabetes is not restricted to HLA-DR4-positive individuals

Type 1 or insulin-dependent diabetes mellitus (IDDM) is an autoimmune disease of the insulin-producing pancreatic beta-cells which is determined by both genetic and environmental factors. The major histocompatibility complex and the insulin gene region (INS) on human chromosomes 6p and 11p, respectively, contain susceptibility genes. Using a mostly French data set, evidence for linkage of INS to IDDM was recently obtained but only in male meioses (suggesting involvement of maternal imprinting) and only in HLA-DR4-positive diabetics. In contrast, we find evidence for linkage in both male and female meioses and that the effect of the susceptibility gene(s) in the INS region is not dependent on the presence of HLA-DR4.