HLA associations in insulin-dependent diabetes: search for heterogeneity in different groups of patients from a homogeneous population

Human Leukocyte Antigens (HLA) Genes Association in Type 1 Diabetic Nephropathy

BACKGROUND

Diabetic nephropathy is a common worldwide multifactorial disease where involvement of genetic factors is well etablished. The aim of this study was to investigate the HLA genes implication in the development of type 1 diabetic nephropathy.

METHODS

We performed a case- control study where one hundred and fifty subjects were examined. Patients were divided in two groups; with and without type 1 diabetic nephropathy. HLA typing was performed using Polymerase Chain Reaction- Sequence Specific Oligonucleotide (PCR- SSO) method. HLA association to clinical phenotype and HLA haplotype analysis was also investigated.

RESULTS

HLA B*51 is increased in patients without type 1 diabetic nephropathy (7.14% vs. 0 %, P <0.05, OR= 0), however no other studied alleles seem to have any effect (all P>0.05). Haplotype analysis also does not reveal any significant association, however, A*02-B*18-DRB1*03-DQA1*05- DQB1*03 haplotype shows a tendency to be associated with the development of diabetic nephropathy (P = 0.05).

CONCLUSION

These results suggest a protective effect of HLA B*51 allele from type 1 diabetic nephropathy. However, further studies are required in order to clarify its potential implication as a protective marker.

HLA-DRB1*03 as a risk factor for microalbuminuria in same duration of type 1 diabetes: a case control study

BACKGROUND

Increased urinary albumin excretion rate is the earliest clinical manifestation of diabetic nephropathy. The development of microalbuminuria in patients with type 1 diabetes mellitus (T1D) usually begins 5 to 15 years after the onset of diabetes. The rate of progression of diabetic nephropathy varies considerably among patients and not always can be explained solely by glycaemic control. The evidence suggests that genetic susceptibility may play a role in the development of diabetes microvascular complications, besides the presence of such risk factors as hyperglycaemia, hypertension, dyslipidaemia and smoking. The aim of the study was to evaluate a link between known genetic risk factors for type 1 diabetes mellitus (HLA-DR3/DR4) and microalbuminuria among patients with the same durations of diabetes.

METHODS

Ninety-nine patients with T1D at the age 18-35 years were recruited for the study. The urine albumin excretion rate was normal when <30 mg/24 h; microalbuminuria 30-300 mg/24 h. Genotypes were investigated in 39 patients with normal albumin excretion rate and duration of diabetes 13.46 ± 3.72 years and in 60 patients with microalbuminuria and duration of diabetes 15.28 ± 4.08 years (p = 0.11). Genetic typing of DR3 and DR4 antigens successfully was performed for 99 subjects. Statistical analysis was performed using SPSS v. 20.0.

RESULTS

Genotyping of 99 patients with T1D was performed: no DR3 and DR4 risk alleles were found in 22 (22.22 %) cases, DR3 alleles were present in 47 (47.48 %) cases, DR4 alleles in 25 (25.25 %) cases, and DR3/DR4 alleles in 5 (5.05 %) cases. The highest 24 h albumin excretion rate was found in patients with DRB1 gene expressed DR3 risk alleles group, the lowest - in patients with DRB1 gene with no expression of both DR3 and DR4 antigen. We confirmed the 1.87 (p = 0.021) increased relative risk for microalbuminuria in patients with DR3/DR3 alleles and same duration of diabetes. The distribution of DR3 and DR4 risk alleles was not associated with cardiovascular autonomic neuropathy both in patients with normal albumin excretion rate and microalbuminuria (1.6 vs 2.1; p = 0.21).

CONCLUSIONS

The 1.87 (p = 0.021) increased relative risk for microalbuminuria was found in patients with DR3/DR3 alleles and the same duration of diabetes.

Linkage Analysis of Genomic Regions Contributing to the Expression of Type 1 Diabetes Microvascular Complications and Interaction with HLA

We conducted linkage analysis to follow up earlier work on microvascular complications of type 1 diabetes (T1D). We analyzed 415 families (2,008 individuals) previously genotyped for 402 SNP markers spanning chromosome 6. We did linkage analysis for the phenotypes of retinopathy and nephropathy. For retinopathy, two linkage peaks were mapped: one located at the HLA region and another novel locus telomeric to HLA. For nephropathy, a linkage peak centromeric to HLA was mapped, but the linkage peak telomeric to HLA seen in retinopathy was absent. Because of the strong association of T1D with DRB1*03:01 and DRB1*04:01, we stratified our analyses based on families whose probands were positive for DRB1*03:01 or DRB1*04:01. When analyzing the DRB1*03:01-positive retinopathy families, in addition to the novel telomeric locus, one centromeric to HLA was identified at the same location as the nephropathy peak. When we stratified on DRB1*04:01-positive families, the HLA telomeric peak strengthened but the centromeric peak disappeared. Our findings showed that HLA and non-HLA loci on chromosome 6 are involved in T1D complications' expression. While the HLA region is a major contributor to the expression of T1D, our results suggest an interaction between specific HLA alleles and other loci that influence complications' expression.

HLA class I and II alleles are associated with microvascular complications of type 1 diabetes

Although HLA alleles are associated with type 1 diabetes, association with microvascular complications remains controversial. We tested HLA association with complications in multiplex type 1 diabetes families. Probands from 425 type 1 diabetes families from the Human Biological Data Interchange (HBDI) collection were analyzed. The frequencies of specific HLA alleles in patients with complications were compared with the frequencies in complications-free patients. The complications we examined were: retinopathy, neuropathy, and nephropathy. We used logistic regression models with covariates to estimate odds ratios. We found that the DRB1*03:01 allele is a protective factor for complications (OR=0.58; p=0.03), as is the DQA1*05:01-DQB1*02:01 haplotype found in linkage disequilibrium with DRB1*03:01 (OR=0.59; p=0.031). The DRB1*04:01 allele showed no evidence of association (OR=1.13; p=0.624), although DRB1*04:01 showed suggestive evidence when the carriers of the protective DRB1*03:01 were removed from the analysis. The class II DQA1*03:01-DQB1*03:02 haplotype was not associated with complications, but the class I allele B*39:06 (OR=3.27; p=0.008) suggested a strong positive association with complications. Our results show that in type 1 diabetes patients, specific HLA alleles may be involved in susceptibility to, or protection from, microvascular complications.

Extended family history of type 1 diabetes and phenotype and genotype of newly diagnosed children

OBJECTIVE

To determine the frequency of newly diagnosed diabetic children with first- and second-degree relatives affected by type 1 diabetes and to characterize the effects of this positive family history on clinical markers, signs of β-cell autoimmunity, and HLA genotype in the index case.

RESEARCH DESIGN AND METHODS

Children (n = 1,488) with type 1 diabetes diagnosed under 15 years of age were included in a cross-sectional study from the Finnish Pediatric Diabetes Register. Data on family history of diabetes and metabolic decompensation at diagnosis were collected using a questionnaire. Antibodies to β-cell autoantigens (islet cell antibodies, insulin autoantibodies, GAD antibodies, and antibodies to the islet antigen 2 molecule) and HLA genotypes were analyzed.

RESULTS

A total of 12.2% of the subjects had a first-degree relative with type 1 diabetes (father 6.2%, mother 3.2%, and sibling 4.8%) and 11.9% had an affected second-degree relative. Children without affected relatives had lower pH (P < 0.001), higher plasma glucose (P < 0.001) and β-hydroxybutyrate concentrations (P < 0.001), a higher rate of impaired consciousness (P = 0.02), and greater weight loss (P < 0.001). There were no differences in signs of β-cell autoimmunity. The familial cases carried the HLA DR4-DQ8 haplotype more frequently than sporadic cases (74.0 vs. 67.0%, P = 0.02).

CONCLUSIONS

When the extended family history of type 1 diabetes is considered, the proportion of sporadic diabetes cases may be reduced to <80%. A positive family history for type 1 diabetes associates with a less severe metabolic decompensation at diagnosis, even when only second-degree relatives are affected. Autoantibody profiles are similar in familial and sporadic type 1 diabetes, suggesting similar pathogenetic mechanisms.

The role of HLA class I gene variation in autoimmune diabetes

The use of DNA-based genetic typing has enabled the identification of type 1 diabetes mellitus (T1DM) susceptible and protective major histocompatibility complex (MHC) class II alleles and haplotypes. The application of this approach has also progressed to locate MHC class I alleles that contribute to the clinicopathology of T1DM. Recent studies have shown a widespread involvement of genes from the MHC class I gene region in the clinicopathology of T1DM. These genes are shown to be involved in contributing to progression from the preclinical stage of the disease, which is characterized by the occurrence of islet-specific antibodies, to clinical disease and also to the occurrence of autoimmunity. They can either contribute directly to disease development or indirectly in concert with other susceptible MHC class II alleles or haplotypes via linkage disequilibrium. Class I alleles may also be negatively associated with T1DM. These findings are useful for the development of future strategies in designing tolerogenic approaches for the prevention or even reversal of T1DM. In this article, the latest evidence for the different kinds of participation of HLA class I genes in the etiology of T1DM is reviewed. A meta-analysis which included existing association studies was also carried out in order to re-assess the relevance of class I genes in diabetes development. The analysis of an enlarged heterogeneous sample confirmed the involvement of previously detected serotypes in the etiology of T1DM, such as A24, B8 and B18, and revealed hitherto unknown associations with B60 and B62. The analysis points out that much of the conflicting results of previous association studies originate from inadequate sample sizes and accentuate the value of future investigations of larger samples for identifying linkage in multigenic diseases.

Microalbuminuria and mortality in long-duration type 1 diabetes

OBJECTIVE

Microalbuminuria is a recognized risk factor for increased mortality and renal failure in type 1 diabetes. Whether it remains a powerful predictor in patients with a long duration of type 1 diabetes is not known. We ascertained the prognostic significance of abnormal urinary albumin excretion in a cohort of patients with at least 30 years of type 1 diabetes.

RESEARCH DESIGN AND METHODS

A total of 190 patients with a disease duration of type 1 diabetes of at least 30 years with baseline and 5 years of follow-up.

RESULTS

At baseline 66% were normoalbuminuric, and at 5 years 11% of this cohort had died. Of the 22% who were microalbuminuric at baseline, 26% had died, and of the 8% with persistent proteinuria at baseline, 44% had died. Of the 4% with end-stage renal failure at baseline, 71% had died within 5 years. Death was attributable to a cardiovascular cause in two-thirds of the cases in all groups.

CONCLUSIONS

Even in those with a long duration of type 1 diabetes, the presence of abnormal urinary excretion remains a powerful predictor of increased mortality.

HLA-DR3 and DR4 and their relation to the incidence and progression of diabetic retinopathy

PURPOSE

Cross-sectional data from the Wisconsin Epidemiologic Study of Diabetic Retinopathy indicated that patients with HLA-DR4, but not DR3, were more likely to have prevalent proliferative retinopathy than those without both antigens. We describe the relation of HLA-DR3 and DR4 antigens to the 14-year incidence and progression of diabetic retinopathy and macular edema in this cohort.

DESIGN

A population-based cohort study.

PARTICIPANTS

A probability sample of male and female patients receiving primary care for diabetes in 11 counties of southern Wisconsin.

METHODS

Participants were invited for a baseline examination in 1980 to 1982, with follow-up examinations at 4, 10, and 14 years later. At the 4-year examination, a random sample of participants (n = 428) diagnosed with diabetes before the age of 30 and taking insulin were selected for HLA-DR typing.

MAIN OUTCOME MEASURES

Fourteen-year incidence and progression of diabetic retinopathy and macular edema based on masked stereoscopic fundus photographic grading.

RESULTS

There was no relation between HLA-DR3 and DR4 status with the 14-year incidence and progression of diabetic retinopathy, progression to proliferative retinopathy, and incidence of macular edema. Patients with either HLA-DR3 or DR4 were less likely to progress to proliferative retinopathy compared with those who were negative for both, although these relations were not statistically significant. The associations did not vary after adjusting for hypertension status, baseline retinopathy, and glycosylated hemoglobin levels, or after stratifying by duration of diabetes (less than 10 years vs. 10 years or more) and age at diagnosis of diabetes (less than 15 years vs. 15 years or more). Furthermore, 10-year mortality and 14-year nephropathy rates did not differ by HLA-DR3 or DR4 status, suggesting that selective mortality did not explain the pattern of associations seen.

CONCLUSIONS

In contrast to the initial cross-sectional findings, these data suggest that HLA-DR3 or DR4 status is unrelated to 14-year incidence and progression of diabetic retinopathy. The discrepancy may be related to increasing homogeneity of retinopathy and diminishing power to detect small differences, but it may also reflect the uncertain and inconsistent effects of HLA-DR3 or DR4 on the development and progression of diabetic retinopathy.

Autoimmune diabetes not requiring insulin at diagnosis (latent autoimmune diabetes of the adult): definition, characterization, and potential prevention

Type 1 diabetes is caused by the immune-mediated destruction of islet insulin-secreting beta-cells. This chronic destructive process is associated with both cellular and humoral immune changes in the peripheral blood that can be detected months or even years before the onset of clinical diabetes. Throughout this prediabetic period, metabolic changes, including altered glucose tolerance and reduced insulin secretion, deteriorate at variable rates and eventually result in clinical diabetes. A fraction of individuals with humoral immunological changes have clinical diabetes that initially is not insulin-requiring. The onset of diabetes in these patients is usually in adult life, and because their diabetes is at least initially not insulin-requiring, they appear clinically to be affected by type 2 diabetes. Such patients probably have the same disease process as patients with type 1 diabetes in that they have similar HLA genetic susceptibility as well as autoantibodies to islet antigens, low insulin secretion, and a higher rate of progression to insulin dependency. These patients are defined as being affected by an autoimmune type of diabetes not requiring insulin at diagnosis, which is also named latent autoimmune diabetes of the adult (LADA). Special attention should be paid to diagnose such patients because therapy may influence the speed of progression toward insulin dependency, and in this respect, efforts should be made to protect residual C-peptide secretion. LADA can serve as a model for designing new strategies for prevention of type 1 diabetes but also as a target group for prevention in its own right.

Immunogenetics of HLA class II in Israeli Ashkenazi Jewish, Israeli non-Ashkenazi Jewish, and in Israeli Arab IDDM patients

The distribution of HLA class II alleles and genotypes in IDDM patients was examined in the three main Israeli ethnic groups: Ashkenazi Jews, non-Ashkenazi Jews, and Arabs. Molecular sequence specific oligonucleotide probe analysis was performed for DRB1, DQA1, and DQB1 genes. The DRB1*03011, DQA1*05 DQB1*02/DRB1*0402, DQA1*03, DQB1*0302 genotype was found to be the main susceptibility genotype in all three groups, with differences in the degree of association. In addition to DRB1*0402 (more frequent among Ashkenazi Jews), DRB1*0405, another subtype of DRB1*04, was found to be more prevalent among non-Ashkenazi Jews and Arabs. Many alleles were found to be negatively associated with insulin dependent diabetes mellitus (IDDM). This could be a result of the high frequency of susceptible alleles, or of linkage disequilibrium to a primary negatively associated allele. The strongest negative association was observed for DQB1*0301 in all three ethnic groups. The alleles DRB1*1401, DRB1*1501, DQB1*05031, DQB1*0602, and DQB1*0609 were not detected in any of the 202 IDDM patients, and are probably either strongly protective or in linkage with such alleles. Despite the differences found between the three ethnic groups, an overall analysis shows that the DRB1*04 alleles that account for susceptibility to IDDM in the Israeli population (DRB1*0402 and *0405) are the same as those responsible for susceptibility to IDDM in a number of other Mediterranean populations. In contrast, the susceptible allele in most Caucasian populations is DRB1*0401. It is noteworthy that the susceptible alleles DRB1*0402/05 for Mediterranean and DRB1*0401 for Caucasian populations are also frequent in the respective healthy populations. These findings support the results obtained in other studies, which point to a genetic relationship between the Israeli and Mediterranean populations.

Contribution of HLA class II genes to end stage renal disease in mexican patients with type 2 diabetes mellitus

To analyze the contribution of MHC class II genes in type 2 diabetes mellitus (DM) with end stage renal disease (ESRD), we examined the distribution of HLA-DRB1, DQA1, DQB1 loci in Mexican Mestizos of Central Mexico, using PCR-SSOP and PCR-SSP. Three groups were included: 47 type 2 diabetic ESRD patients; 42 patients with ESRD and 50 type 2 DM patients with no kidney complication. The results were compared with those of 101 controls of the same area. The median since DM was first diagnosed, was 18 years prior to the onset of ESRD. The frequencies of DRB1*1502 and DQB1*0501 were increased in DM patients with ESRD (p = 0.004; RR = 7.4, CI = 1.5-37; EF = 0. 13; p = 0.007; RR = 2.9, CI = 2.3-3.5, EF = 0.21, respectively). In contrast, DRB1*0407 was decreased in the same group (p = 0.0008, RR = 0.2; CI = 0.035-0.70, PF = 0.19). Diabetic patients with DRB1*1502 are 8.8 times more likely to develop ESRD, independently of the duration time of DM. DRB1*1502 contributes to the susceptibility to ESRD while DRB1*0407 is involved in protection. The residue at DRB1-74 differs in these alleles: DRB1*0407 has glutamic acid and DRB1*1502 has an alanine, suggesting that this substitution may be important for both, peptide anchoring and for presentation to the T cells.

Associations of MHC class II alleles with insulin-dependent diabetes mellitus (IDDM) in patients from North India

Thirty-four insulin-dependent diabetes mellitus (IDDM) patients from North India were studied with respect to their HLA class II alleles including those of the DRB1, DQA1, DQB1 and DPB1 loci, using the polymerase chain reaction (PCR) and hybridization with sequence-specific oligonucleotide probes (SSOP). They were compared with the class II alleles of 94 normal adult controls from the same ethnic background. The results show a statistically significant increase of DRB1*03011 (p < 0.00001), DQB1*0201 (p < 0.007), DQA1*0501 (0.0027) and DPB1*2601 (p < 0.0042) in patients compared to controls. DR*04 was not significantly increased. However, homozygosity for DRB1*03011 was increased more than expected. DRB1*1501 and *1502 did not show a significant decrease in the patients. However, DRB1*0701 was decreased significantly, but this difference did not remain significant when the p value was corrected for the number of alleles tested. Similarly, DPB1*2601 was increased significantly in the patients but did not remain significant after p was corrected for the number of alleles tested. However, DPB1*2601 was increased, and remained significant after correction, in patients not having HLA-DR3. We also studied the possible role of aspartic acid at codon 57 of the DQ beta chain in protection against development of diabetes, and arginine at codon 52 of the DQ alpha chain in susceptibility. We observed an increase in non-Asp57 alleles in DQ beta and Arg52 in DQ alpha in the patients, however, this effect seems to be due to the fact that the most prevalent haplotype in diabetic patients: DRB1*03011-DQA1*0501-DQB1*0201, has DQB1 and DQA1 alleles which carry non-Asp57 and Arg52, respectively.

TNFalpha*2 marks high risk of severe disease during Plasmodium falciparum malaria and other infections in Sri Lankans

We have investigated the association between alleles of the genes for tumour necrosis factor-alpha (TNF-alpha) and TNF-beta and severity of disease during malarial (Plasmodium falciparum) and other infections in the Sri Lankan population. Patients were categorized as having either (i) uncomplicated malaria, (ii) severe and complicated malaria, or (iii) severe and complicated infection in which a diagnosis of malaria had been excluded. For all the patients, as well as for a group of matched healthy controls, TNF-alpha and TNF-beta allelic types were identified using the polymerase chain reaction (PCR) and allele-specific oligonucleotide probes and restriction enzyme digestion. The odds in favour of carrying the TNFalpha*2 allele, mainly of the heterozygous genotype (TNFalpha*1,*2), were two to three times greater among individuals with severe disease, of either malarial or other infectious origin, relative to healthy controls or to those with uncomplicated malarial infections. No significant risk was associated with either of the alleles of TNF-beta.

HLA class II immunogenetics of IDDM in Yemenite Jews

The association between HLA-DR and DQ and insulin dependent diabetes mellitus (IDDM) was analyzed in 47 patients and 76 controls of Yemenite Jewish origin. The IDDM susceptibility alleles DRB1*03011, DQA1*0501, DQB1*02 and DRB1*0402, DQA1*0301, DQB1*0302 found in Caucasians had a very strong predisposing effect also in the Yemenite IDDM group. The DRB1*07, DQA1*0201 and DQB1*02 alleles were found to have a strong negative association with IDDM. None of the patients carried DRB1*07 and DQA1*0201 compared with healthy controls (43.7%). Our analysis revealed that the DRB1*03011 DQA1*0501 DQB1*02/DRB1*04 DQA1*03 DQB1*0302 heterozygous genotype confers the highest susceptibility (59.6% in patients vs. 0% in controls). The homozygous DRB1*03 and DRB1*04 genotypes were also found to be positively associated with the disease. 81% of the patients compared to 1.3% of controls carried the susceptibility alleles on both haplotypes. In conclusion, the development of IDDM in Yemenite Jews is strongly dependent on the presence of the susceptibility HLA alleles and on the absence of the DRB1*07 haplotype. The Yemenite Jewish group is uniquely homogenous with regard to genetic susceptibility factors involved in the process of IDDM, and may thus be an ideal model for further genetic studies.

HLA-DQB1-defined genetic susceptibility, beta cell autoimmunity, and metabolic characteristics in familial and nonfamilial insulin-dependent diabetes mellitus. Childhood Diabetes in Finland (DiMe) Study Group

Familial aggregation of insulin-dependent diabetes mellitus (IDDM) is a common phenomenon, but the reasons behind it are poorly understood. To investigate whether there is heterogeneity between familial and nonfamilial forms of IDDM we compared genetic, immunological, and clinical characteristics of diabetic children with and without an affected first-degree relative in a population-based series of Finnish children with IDDM. The frequencies of HLA-DQB1 genotypes known to be associated with high (DQB1*0302/0201) or moderate (*0302/x) IDDM risk in the Finnish population were increased, while the proportions of DQB1 genotypes associated with low or decreased risk for IDDM were reduced in the 121 familial cases as compared with the 574 nonfamilial cases (32.7 vs. 21.3%, 41.3 vs. 35.9%, 18.3 vs. 31.4%, and 7.7 vs. 11.4%, respectively; P = 0.002). The frequencies and serum concentrations of islet cell antibodies, insulin autoantibodies, and antibodies to the 65-kD isoform of glutamic acid decarboxylase were similar at diagnosis in the familial and nonfamilial cases. The 31 first-affected cases in the multiple case families were younger at diagnosis than the nonfamilial cases (6.9 vs. 8.5 yr; P < 0.05). The 90 second-affected familial cases had less severe metabolic decompensation at diagnosis than either the first-affected familial or nonfamilial cases. In conclusion, familial aggregation of IDDM in Finland is at least partly explained by a higher frequency of IDDM susceptibility genes in families with multiple affected individuals. The lack of differences in autoantibody levels between the familial and nonfamilial cases indicates homogeneity rather than heterogeneity in the pathogenetic process of beta cell destruction.

Effect of polymorphism in the insulin gene region on IDDM susceptibility and insulin secretion. The Childhood Diabetes in Finland (DiMe) Study Group

In addition to the major genetic determinants of insulin-dependent diabetes mellitus (IDDM) in the major histocompatibility complex (MHC) on chromosome 6, there are also minor genetic risk markers, e.g. in the insulin gene region on chromosome 11p15.5 (IDDM2). We studied the significance of the-23 HphI polymorphism in the insulin gene region (-23 HphI INS) in the Finnish population in combination with HLA genotyping data. The frequency of the-23 HphI INS +/+ genotype was higher in diabetic subjects with a low risk HLA DQB1 genotype than in control subjects (P = 0.05). Diabetic children in multiple-case families also had a higher frequency of the INS risk genotype than the controls (P < 0.05), and this difference was independent of the HLA genotype. Furthermore, we studied siblings positive for islet cell antibodies (ICAs) and/or insulin autoantibodies (IAAs) to evaluate the impact of the-23 HphI INS +/+ genotype on their beta-cell function assessed by sequential intravenous glucose tolerance tests and on their progression to IDDM. When analysing siblings with a low-risk HLA DQB1 genotype, those with the-23 HphI INS +/+ genotype had lower first phase insulin responses (P < 0.02) on several occasions than the remaining sibling. Six siblings (26.1%) in the former group progressed to clinical disease during the observation period, whereas none in the latter group presented with IDDM (P = 0.01). These observations suggest that the-23 HphI INS +/+ polymorphism is associated with an increased risk of IDDM in subjects without predisposing genes in the MHC region. The enhanced susceptibility may be related to a reduced insulin secretory capacity.

HLA antigens and age at diagnosis of insulin-dependent diabetes mellitus

IDDM results from the immune-mediated destruction of pancreatic islet beta cells. Clinicopathologic heterogeneity in IDDM is reflected in part by the wide age range over which the onset of clinical symptoms can occur, after months to years of subclinical "insulitis." Because MHC genes play a critical role in immune function we studied their possible contribution to IDDM heterogeneity by analyzing HLA profiles of 194 IDDM patients in relation to their age at diagnosis. Restriction of HLA-DR heterogeneity was observed in patients diagnosed before age 21 years. Frequencies of DR3 and DR3/4 were highest in the < or = 6-year-old age group and thereafter declined with increasing age at diagnosis. In contrast, the frequency of DR4 remained increased up to age 30 years at diagnosis. DR7, normally considered to be a neutral allele, was like DR2 and DR5, significantly decreased in patients diagnosed before age 21 years. The A30-B18-DR3 haplotype was significantly increased in the < or = 6-year-old age group, A1-B8-DR3 was increased in the > or = 31-year-old group. B62-DR4 was increased only in the > 12-year-old age group. In DR4 patients the frequency of DQ8 was increased across all age groups. A sex difference was observed in those diagnosed at < or = 12 years of age, with an excess of females in the DR3+/DR4- group and males in the DR3-/DR4+ group. An association of DPB1 with IDDM was revealed by an increased frequency overall of DPB1*0301 and/or DPB1*0401, being more pronounced in patients diagnosed at > 20 years of age.(ABSTRACT TRUNCATED AT 250 WORDS)

T cell proliferative responses to glutamic acid decarboxylase-65 in IDDM are negatively associated with HLA DR3/4

Based on studies in spontaneously non-obese diabetic (NOD) mice, it has been suggested that the Mr 65,000 isoform of glutamic acid decarboxylase (GAD65) is of major importance in the pathogenesis of insulin-dependent diabetes mellitus (IDDM). In humans, antibodies to GAD65 are present before and at onset of the disease and in vitro T cell reactivity to GAD has also been reported. To further characterize the T cell recognition of GAD65, we incubated peripheral blood mononuclear cells from 45 newly diagnosed IDDM patients with purified recombinant human islet GAD65 and correlated the proliferative response with HLA DR haplotype and the presence of GAD65 autoantibodies. Fifty healthy individuals were studied as controls. Of the patients, 49% showed proliferative responses to GAD65 in contrast to only 4% of the controls. T cell proliferation to GAD65 was significantly more frequent in patients not being HLA DR3/4 heterozygous (19/29, 66%) as compared to HLA DR3/4 heterozygous patients (3/16, 19%) (p < 0.01). The difference was most pronounced in females with 64% (9/14) of the HLA non-DR3/4 patients being positive compared to none (0/6) of the HLA DR3/4 patients (p < 0.05). The overall frequency of GAD65 autoantibodies was 71% (32/45) with a similar distribution between patients with HLA DR3/4 (10/16, 63%) and HLA non-DR 3/4 (22/29, 76%). There was no correlation between levels of the T and B cell responses to GAD65 (r = 0.24). In conclusion, we find a proliferative T cell response to GAD65 in approximately 50% of recent onset IDDM patients and unexpectedly find the majority of responders to be HLA non-DR 3/4 heterozygous patients. No difference was observed in B cell responsiveness between the two HLA groups.

TNF Nco-I RFLP is not an independent risk factor in rheumatoid arthritis

The human TNF genes are located within the MHC class-III region on chromosome 6. The presence or absence of an Nco-I restriction site in the 5' non-coding sequence of the TNF beta gene defines two alleles (TNFB*1 and TNFB*2). The segregation of these alleles has been associated with levels of TNF alpha or TNF beta production in systemic lupus erythematosis (SLE), insulin-dependent diabetes mellitus (IDDM) and in healthy control individuals. Rheumatoid arthritis (RA) is characterized by high levels of TNF alpha within the synovial fluid and to address the question of whether this could be brought about by a genetic predisposition to high TNF production by RA individuals, we examined the distribution of this Nco-I polymorphism in 98 healthy volunteers and 123 patients with active rheumatoid arthritis. No difference was observed between the normal and RA groups with respect to haplotype segregation or allelic frequency. Furthermore, no difference was observed between DR4+ or DR4- individuals in the control or RA groups. These data demonstrate that the high level of TNF alpha seen in the joints of RA patients is unlikely to be due to a genetic predisposition of these patients to high TNF alpha production, as defined by the TNF Nco-I restriction fragment length polymorphism (RFLP).

Incidence of insulin-dependent diabetes mellitus in age groups over 30 years in Denmark

The incidence of IDDM in the age group over 30 years was estimated in a historical prospective study, using clinical and biochemical measurements at onset as criteria for classification. The study population, nearly one million, represents 20% of the Danish population. The degree of ascertainment was > 99%. One thousand two hundred and forty patients were treated with insulin during the study period (1973-77). Based on the clinical and biochemical variables, the patients were classified into three groups: insulin-dependent diabetes mellitus (IDDM) accounted for 16.2%, insulin-treated diabetes mellitus for 54.1% and short-term treated diabetes mellitus for 29.6% of the total insulin-treated group. The incidence of IDDM in the age group over 30 years at onset was 8.2 100,000(-1) year-1. The cumulative incidence rate (0-90 years) was 1.5-1.6 per cent. The present study indicates that IDDM may develop at any age. Thus the life-time risk of developing IDDM is higher than hitherto expected.

Long-term risk of IDDM in first-degree relatives of patients with IDDM

Due to a short observation period previous studies may have underestimated prevalence and recurrence risk of IDDM in relatives of IDDM patients. To obtain a more exact life-time risk estimate we identified 310 probands, representative of Danish IDDM patients, characterized by current age more than 50 years, age at onset 40 years or less and diabetes duration of more than 30 years. Family data were obtained from 291 probands. Mean "observation" times (age) (+/- SD) for siblings (n = 553) and offspring (n = 359) were 59.4 +/- 16.1 years and 33.8 +/- 8.8 years, respectively. Of the probands 73 (25.1%) had at least one first-degree relative with IDDM. Seventeen percent had at least one affected sibling. An increase from 10.4% to 22.4% of having first-degree relatives with IDDM among probands with age at onset below 20 years was observed during the period from proband at age 21 years up to 1 September 1992. Among affected siblings 48% of the second cases were affected more than 10 years after the first affected sibling. Using the life-table method cumulative recurrence risks from time of birth were calculated for siblings up to age 30 years of 6.4% and up to age 60 years of 9.6%. For offspring the risk up to age 34 years was 6.3%. In addition, we present a life-table method evaluating the cumulative recurrence risk from time of onset in the proband, as this is the most relevant when giving genetic counselling. In conclusion, the long-term risks of IDDM in siblings and offspring are high compared to that shown in previous reports.

HLA and disease associations: detecting the strongest association

A major aim of HLA and disease association studies is to identify the causative HLA factor truly responsible for the association. This is usually difficult due to the pronounced linkage disequilibrium between most HLA determinants. The causative factor must show the strongest association compared to all other factors. Here we describe a simple analysis which can be used to identify which of two factors, say A and B, shows the strongest association. The basic data for the analysis are the entries of the two-by-four table giving the four phenotypic combinations of A and B in patients and controls, respectively. These data are analyzed in various two-by-two tables involving stratification of each of the two factors against the other. A stronger increase of factor A is established if A is significantly associated with the condition both in B-positives and in B-negatives, when this is not true for B in A-positives and A-negatives. Using simulation with control data, it is demonstrated how linkage disequilibrium may influence secondary associations. The analysis may also be used to investigate interaction between HLA factors, but linkage disequilibrium complicates the interpretation in such cases. The method is exemplified using various published data. Finally, some statistical recommendations are given. Thus, we advise that phenotype (marker) frequencies are generally used instead of gene (i.e. allele, or haplotype) frequencies. The importance of correcting p-values, the levels of significance, and the power of Fisher's exact test are discussed.

Genetic susceptibility markers in Danish patients with type 1 (insulin-dependent) diabetes--evidence for polygenicity in man. Danish Study Group of Diabetes in Childhood

Fifty-five Danish families with two offspring concordant for type 1 diabetes--identified through a nationwide population-based survey, and 57 "true sporadic" cases--matched with familial cases for age at onset, but with no IDDM-affected first-degree relatives and long disease duration, and 110 control subjects were typed for putative genetic susceptibility markers for type 1 diabetes identified from a pathogenetic model. The markers included MHC class I, II and III loci, the manganese superoxide dismutase (MnSOD) locus (chr. 6q), interleukin-1 beta (IL1B), the IL-1 receptor antagonist (IL1RN), and the IL-1 type 1 receptor (IL1RI) loci (each chr. 2q). No significant differences between familial and sporadic cases were found within the MHC region (including the following loci: HLA-DQ, -DR, heat shock protein (HSP) 70, tumour necrosis factor (TNF), HLA-B and -A). In both groups of patients 11% were negative for both DQA1*0301-DQB1*0302 and DQA1*0501-DQB1*0201 genotypes, and 7% of the type 1 diabetics had genotypes unable to encode a susceptibility DQ alpha beta heterodimer. Disease association was found for the IL1RN (p = 0.04) and for the IL1RI (p = 0.03). When comparing controls and only familial cases with type 1 diabetes for the IL1RN polymorphism a difference was observed (p = 0.003). For the IL1B RFLP a trend for difference was observed between familial cases and control subjects (p = 0.046), whereas no differences between sporadic cases and control subjects could be demonstrated neither at the IL1B nor at the IL1RN loci. A difference in the MnSOD pattern was observed between sporadic cases and controls (p = 0.04).

No independent association between a tumor necrosis factor-alpha promotor region polymorphism and insulin-dependent diabetes mellitus

Several studies have implicated tumor necrosis factor (TNF)-alpha in the pathogenesis of insulin-dependent diabetes mellitus (IDDM). In the present study we analyzed the first reported TNF-alpha gene polymorphism in relation to IDDM. We have made frequence analysis and tested in vitro lipopolysaccharide (LPS)-induced TNF-alpha secretion. A significant difference in allele frequency was observed between patients and controls (p = 0.03). However, a very strong association of the uncommon TNF2 allele was observed with the HLA-B8, -DR3 alleles. The relative risk (RR) of TNF2 was 2.2 compared to a RR of 3.1 for DR3. One reason for this difference was the identification of the TNF1 allele on the otherwise strongly IDDM-associated HLA-DR3 haplotype: DQB1*0201, DQA1*0501, DRB1*0301, TNFc2, TNFB*2, TNFa1, TNFb5, B18. Thus, the IDDM-associated TNF2 allele had no DR3-independent value as a disease marker. The LPS-induced TNF-alpha production by human monocytes in relation to genotypes demonstrated that TNF1/2 heterozygous individuals had higher, though not statistically significantly (p = 0.08) levels than TNF1-homozygous subjects. However, this difference was rather small, unlikely to be of biological significance and based on the present material we cannot establish the functional importance of this polymorphism.

Association of tumor necrosis factor (TNF) and class II major histocompatibility complex alleles with the secretion of TNF-alpha and TNF-beta by human mononuclear cells: a possible link to insulin-dependent diabetes mellitus

We have investigated the correlation between different tumor necrosis factor (TNF) and class II major histocompatibility complex alleles in the lipopolysaccharide- or phytohemagglutinin-induced secretion of TNF-alpha and TNF-beta by human monocytes and peripheral blood mononuclear cells in 87 unrelated Danish male individuals. Significant differences in TNF-alpha secretory capacity between TNF NcoI restriction fragment length polymorphisms, TNFa and TNFc microsatellite alleles and DR alleles were identified. No correlation with TNF-beta secretory capacity was found for any of the markers studied. TNF genotyping allowed us to define four extended HLA haplotypes which correlate with TNF-alpha secretory capacity. Two of these are DR4 positive: DQw8, DR4, TNFB*1, TNFa6, B44, A2 and DQw8, DR4, TNFB*2, TNFa2, B15, A2. Individuals carrying the TNFB*2, TNFa2 haplotype had a higher TNF-alpha secretory capacity than those carrying the TNFB*1, TNFa6 haplotype. In a group of DR3/DR4 heterozygous patients with insulin-dependent diabetes mellitus (IDDM), the frequency of the TNFa2 allele was higher than in HLA-DR matched controls, whereas the TNFa6 allele was more frequent in control individuals. In the DR3/DR4 heterozygous diabetic group 12/26 had the alleles combination DQw8, DR4 (Dw4), C4A3, TNFB*2, TNFa2, B15, whereas only 1/18 controls had this haplotype. This diabetogenic haplotype is identical to the DR4 haplotype which correlates with a higher TNF-alpha response. These observations suggest a direct role for the TNF locus in the pathogenesis of IDDM.

Type I diabetic nephropathy: clinical characteristics and economic impact

Approximately one-third of type I diabetic patients develop diabetic nephropathy with confounding pathogenesis--frequently manifested as heavy persistent proteinuria, fall in glomerular filtration rate, and increased arterial hypertension. There is increasing incidence and prevalence of type I diabetes, particularly in northern Europe and the United States. Increased morbidity and mortality occur in type I diabetic patients with renal disease. Among type I patients with persistent proteinuria, death occurs on the average within 5-10 years. The economic impact of endstage renal disease due to diabetic nephropathy is overwhelming, and the cost is increasing at an alarming rate.

A TaqI polymorphism in the human interleukin-1 beta (IL-1 beta) gene correlates with IL-1 beta secretion in vitro

In the present study we searched for restriction fragment length polymorphisms (RFLP) in the human interleukin-1 beta (IL-1 beta) gene and for correlations to monocyte (Mo) function in non-related healthy donors and insulin-dependent diabetic patients. We demonstrated a diallelic polymorphism with the restriction enzyme TaqI consisting of fragments of 9.4 kb and 13.4 kb. No differences in allele or genotype frequencies of this RFLP were observed between randomly selected controls and randomly selected patients with insulin-dependent diabetes mellitus (IDDM). However, when analysing IDDM patients negative for HLA-DR3 and -DR4, our data demonstrate that the 13.4 kb allele is more frequent in this group compared to a matched control group. The functional impact of this RFLP was studied by analysing in vitro stimulated Mo IL-1 beta response. An IL-1 beta allele dosage effect on secretory capacity was observed after LPS-stimulation: 13.4/13.4 kb homozygous individuals secreted significantly more IL-1 beta than 9.4/13.4 kb heterozygous individuals, who secreted significantly more than 9.4/9.4 kb homozygous individuals. Analyses of supernatants from LPS-stimulated Mo cultures from individuals with each TaqI IL-1 beta genotype revealed no differences in the mouse thymocyte co-stimulatory assay when compared on a molar basis, indicating that the TaqI polymorphism gave rise only to quantitative differences in expression levels and probably not to a mutant IL-1 beta.(ABSTRACT TRUNCATED AT 250 WORDS)

Can autoimmune mechanisms account for the genetic predisposition to schizophrenia?

Applications of molecular genetic techniques to schizophrenia have shown great initial promise but have then proved disappointing. In order to maximise chances of elucidating the genetic mechanism underlying schizophrenia, diverse strategies and diverse perspectives must be adopted. Most studies begin with the premise that, although schizophrenia may be a heterogeneous collection of diseases, some subtypes will be primarily single-gene disorders. We are concerned that this single-gene hypothesis may be incorrect. Schizophrenia research may benefit from application of knowledge from other disciplines and from other diseases which, in terms of epidemiology and apparent genetic mechanisms, bear some resemblance to schizophrenia.

Complementation of HLA-DQA and -DQB genes confers susceptibility and protection to insulin-dependent diabetes mellitus

Lack of an aspartic acid 57 in the HLA-DQ beta chain was introduced as a genetic marker of insulin-dependent diabetes mellitus (IDDM). Because 25% of the control population carries the same marker, we analyzed the DQ locus for the presence of more specific disease susceptibility markers, taking into account a possible role for the polymorphic DQA gene. We thereby identified the DQA3-DQB3.2/DQA4.1-DQB2 (DQA1*0301-DQB1*0302/DQA1*0501-DQB1*0201) genotype which was detected in 30% of the 268 typed IDDM patients and only in 1% of the 331 typed healthy controls, resulting in a relative risk of 35. This genetic marker was more frequent in patients with clinical onset before age 18 years (36%) than in patients diagnosed between age 18 and 40 years (22%) and was not observed in patients with non-IDDM. The new susceptibility genotype DQA3-DQB3.2/DQA4.1-DQB2 (DQA1*0301-DQB1*0302/DQA1*0501-DQB1*0201) may explain the well-known excess of DR3/DR4 heterozygous IDDM patients and is expected to help identify individuals at risk for developing the disease.

Familial and sporadic insulin-dependent diabetes: evidence for heterogeneous etiologies?

Heterogeneity within insulin-dependent diabetes mellitus (IDDM) has been hypothesized, but few studies have focused on differences which may exist between familial and sporadic IDDM cases. Presenting characteristics for 330 white, newly diagnosed IDDM cases were evaluated. Familial cases were older (10.2 +/- 5.1 years vs 7.9 +/- 4.2 years, P = 0.010) and had, on average, less severe metabolic disturbances at presentation, as demonstrated by lower mean hemoglobin A1 (12.6 +/- 2.4% vs 14.4 +/- 2.6%, P = 0.001) and mean insulin dose at discharge (0.62 +/- 0.35 U/kg/day vs 0.85 +/- 0.29 U/kg/day, P less than 0.001), and higher mean plasma bicarbonate concentrations (19.3 +/- 3.9 mmol/l vs 15.8 +/- 5.9 mmol/l, P = 0.023) and mean plasma C-peptide levels (0.35 +/- 0.36 pmol/ml vs 0.14 +/- 0.15 pmol/ml, P less than 0.001). Further analyses on a subset of IDDM cases (n = 100) indicated that initial differences in metabolic indices observed at diagnosis were no longer apparent at one-year post-diagnosis. These results suggest that the etiology of familial and sporadic IDDM is similar and that the less severe presentation observed at diagnosis in the familial cases may be due to earlier identification of the disease, reflecting increased parental knowledge of diabetic symptoms and/or frequent testing for diabetes.

The role of genetic predisposition to type I (insulin-dependent) diabetes mellitus

The aetiology of insulin-dependent diabetes (IDDM) involves genetic predisposition, a major component of which has been mapped in the HLA complex, near to or identical with genes encoding class II molecules. In Caucasian populations IDDM is strongly associated with the serologically defined HLA-DR3 and DR4 antigens, which are widely recognised as markers of susceptibility. The particularly high risk of DR3/DR4 heterozygotes suggests that susceptibility is determined by two genes acting synergistically. The development of recombinant DNA technology has allowed a finer description of the class II region and provided evidence that DQ rather than DR determinants may primarily influence IDDM susceptibility. The search for specific structural changes of the DQA and DQB genes has shown that susceptibility correlates with the absence of aspartic acid at position 57 on the DQ beta chain (DQ beta 57 Asp--) and/or the presence of arginine at position 52 on the DQ alpha chain (DQ alpha 52 Arg+). In Caucasians the formation of a putative DQ susceptibility molecule (DQ alpha 52 Arg+, DQ beta 57 Asp-) accounts best for the disease associations when transcomplementation molecules consisting of DQ alpha and beta chains encoded by different haplotypes are postulated to explain the excess risk of heterozygotes. The HLA-IDDM associations in the Japanese, however, are not explained by this model. These and other unresolved questions indicate that other residues of the DQ alpha and beta chains or other class II molecules (DR beta chains), as well as non-MHC genes, may also contribute to the susceptibility.

A new HLA-DR2 extended haplotype is involved in insulin-dependent diabetes mellitus susceptibility

To ascertain why HLA-DR2 seems to confer only a moderate resistance to insulin-dependent diabetes mellitus (IDDM) in the high-incidence population of Sardinia, Italy, 32 families having one individual affected with IDDM (the proband) and 31 families without IDDM history were randomly selected from the same geographical area and serologically and molecularly HLA typed. The 64 haplotypes of the probands were then compared with the 122 haplotypes determined in the parents from the control families. Two haplotypes were found to have the highest percentage in the general population (12.3% and 7.3%, respectively). The first is the already described "Sardinian" extended haplotype A30, Cw5, B18, 3F130, DR3, DRw52, DQw2 (39.0% in IDDM patients). The second is an extended haplotype that has not been identified before (A2, Cw7, B17, 3F31, DR2, DQw1), and, due to the DR2 allele, we expected it to be decreased in IDDM. However, a stratified analysis performed by removing the DR3 and DR4 haplotypes showed that the frequency of this haplotype is significantly increased in IDDM patients. A peculiar feature of this haplotype is its DQw1 allele, which is DQB1*0502 and has serine in position 57 of the DQ beta chain. The absence of an aspartic acid in this position seems to confer susceptibility to IDDM and not resistance. The fact that DQB1*0502 was present in 75% of the Sardinian DR2 haplotypes may explain why, in Sardinia, DR2 is not providing the commonly recognized resistance to IDDM.

Shared genetic susceptibility of type 1 (insulin-dependent) and type 2 (non-insulin-dependent) diabetes mellitus: contributions of HLA and haptoglobin

Epidemiologic data suggest that having a parent with Type 2 (non-insulin-dependent) diabetes mellitus increases the risk for Type 1 (insulin-dependent) diabetes in siblings of a Type 1 diabetes proband. This increase in risk is consistent with a shared genetic susceptibility between Type 1 diabetes and Type 2 diabetes. We contrast genetic risk factors in three sets of families, consisting of (1) a single Type 1 diabetic child (proband) and non-diabetic parents, (2) multiple Type 1 diabetic siblings and non-diabetic parents, and (3) at least one Type 1 diabetic child and at least one Type 2 diabetic parent. Previous studies have demonstrated that HLA region genes, which elevate the risk in Type 1 diabetes, have no significant effect with respect to the risk for developing Type 2 diabetes. An earlier report cited a contribution by the haptoglobin locus to genetic susceptibility for Type 2 diabetes. We provide evidence that a high risk HLA antigen (HLA-DR3) is decreased to a greater extent in Type 1 patients with a Type 2 parent than in Type 1 patients in which the parents are not diabetic. The role of HLA-DR4 is maintained in these families, with an unexpectedly significant increased rate of transmission of the HLA-DR4 allele from Type 2 parent to Type 1 offspring. The role of haptoglobin in these families does not appear to be important, either with respect to association with diabetes or with respect to linkage with a secondary susceptibility locus. These results indicate that families with a Type 2 parent and Type 1 child, heavily determined by HLA-DR4 linked factors, may represent a homogeneous subset of diabetes susceptibility.

A tumour necrosis factor beta gene polymorphism in relation to monokine secretion and insulin-dependent diabetes mellitus

HLA-class III region genes may be associated with susceptibility to insulin-dependent diabetes mellitus (IDDM). In this study an NcoI polymorphism of the tumour necrosis factor beta (TNF-beta) gene, which is positioned next to the tumour necrosis factor alpha (TNF-alpha) gene in the HLA class III region, was detected by restriction fragment length polymorphism (RFLP). This polymorphism has previously been reported to be located in the TNF-alpha gene. Caucasian HLA-DR3,4 heterozygous IDDM patients (n = 26) and DR-matched healthy controls (n = 19), as well as randomly selected IDDM patients (n = 27) and controls (n = 25) were studied. In addition four multiplex families (49 individuals) and eight HLA-non-identical sibpairs concordant for IDDM were analysed. The TNF-beta gene RFLP analysis showed fragments of 5.5 kb and 10.5 kb, which behaved as alleles. In all groups there was a haplotype assignment of the TNF-beta 5.5-kb allele to B8,DR3 haplotypes, and of the TNF-beta 10.5-kb allele to B15,DR4-positive haplotypes. The allelic and genotypic frequencies differed between DR3,4 IDDM patients and DR3,4 controls, and the DR3,4 control group differed significantly from the randomly selected control group (P less than 0.0079). In HLA-DR3,4- and DQw8-positive persons, the DR3 haplotypes carried the 10.5-kb allele three times more frequently in IDDM patients than in controls, suggesting that the 10.5-kb allele when present on DR3 haplotypes may contribute to susceptibility to IDDM in DR3,4 heterozygous individuals. A contributory role of the 10.5-kb allele in genetic IDDM susceptibility was supported by the sibpair analysis, in which all were TNF-beta identical. Five were 10.5 kb homozygous, and the remaining three pairs were 5.5/10.5 kb heterozygous. Twenty-five healthy and eight newly diagnosed IDDM patients were randomly selected to study the Escherichia coli lipopolysaccharides (LPS)-purified protein derivate (tuberculin) (PPD)-, and phytohaemagglutinin (PHA)-stimulated monocyte (Mo) secretions of interleukin 1 beta (IL-1 beta) and TNF-alpha in relation to the NcoI TNF-beta gene polymorphism. The LPS- and PHA-stimulated Mo IL-1 beta and TNF-alpha secretions were significantly lower for the TNF-beta 5.5/10.5 kb heterozygous individuals than for TNF-beta 10.5 kb homozygous individuals. Furthermore, the Mo IL-1 beta and TNF-alpha secretions of IDDM patients were significantly higher than the Mo secretions of TNF-beta genotype-matched healthy controls. This study suggests an association between the 10.5 kb TNF-beta allele and IDDM, and demonstrates an association between monokine responses and TNF-beta genotypes.(ABSTRACT TRUNCATED AT 400 WORDS)

A T cell receptor beta chain polymorphism is associated with patients developing insulin-dependent diabetes after the age of 20 years

We have studied the BglII polymorphism near the T cell receptor beta chain constant region (TcR-C beta) gene, HLA-DR genotypes and certain autoimmune features in 102 patients with type I (insulin-dependent) diabetes. There was a significant decrease in the frequency of the 1:1 genotype (P = 0.008) and an increase in the 1:2 genotype (P = 0.03) of the BglII TcR polymorphism in the group of patients who developed type-I diabetes after the age of 20 years. This group of patients also showed an increased incidence of autoantibodies (especially islet cell antibody), a family history of diabetes and the presence of other autoimmune diseases. The frequency of this polymorphism in patients who developed type I diabetes before the age of 20 years was similar to a non-diabetic group. These results suggest that there are two genetically distinct groups of patients with type I diabetes. HLA-DR3 and HLA-DR4 genotypes were also increased in the diabetic patients but no significant difference was observed between HLA-DR genotypes, the TcR-C beta genotypes, the age of diagnosis or with other autoimmune features. Patients developing type I (insulin-dependent) diabetes after the age of 20 years have an additional genetic susceptibility for diabetes associated with the TcR-C beta gene.

Monocyte function in IDDM patients and healthy individuals

Interleukin 1 beta (IL-1 beta) and tumour necrosis factor alpha (TNF-alpha) may be pathogenetically important in insulin-dependent diabetes mellitus (IDDM), which is associated with genes of the HLA region. Since a regulatory role of HLA region genes on monokine production may exist, we looked for an association between the monokine and prostaglandin E2 (PGE2) responses of monocytes (Mo) from 20 healthy males (18-50 years) with HLA-DR types relevant for IDDM susceptibility and resistance (DR1,2, DR1,3, DR1,4, DR3,4). Monokine assays were established and evaluated and the secretions of IL-1 beta, TNF-alpha, and PGE2 measured in Mo cultures (2h, 6h, 20h) prepared by endotoxin-free techniques and stimulated by low-dose E. coli lipopolysaccharides (LPS). There were no significant associations between Mo responses and HLA-DR phenotype. Likewise, Mo from DR2 (n = 5) and DR4 (n = 5) homozygous healthy males demonstrated no significant differences in monokine and PGE2 responses of Mo. In the HLA class III region a diallelic TNF-beta gene NcoI polymorphism consisting of alleles of 5.5 kb and 10.5 kb was recently described and associated with susceptibility to autoimmune diseases including IDDM. We report that IL-1 beta and TNF-alpha responses of Mo from TNF-beta 10.5 kb homozygous healthy individuals were significantly higher than for TNF-beta 5.5/10.5 kb heterozygotes. IL-1 beta and TNF-alpha responses of Mo from males (18-35 years) with newly diagnosed (n = 10) and long-standing IDDM (n = 10) and from age- and HLA-DR-matched healthy males (n = 10) were studied. LPS, gamma interferon (IFN), and TNF-alpha-stimulated Mo cultures were investigated. No significant differences were found between Mo responses of IDDM patients and controls. IFN (1000 U/ml) in the presence of LPS significantly potentiated LPS-stimulated Mo TNF-alpha secretion and reduced the levels of IL-1 beta immunoreactivity in Mo lysates. IFN and TNF-alpha did not have any effects on LPS-stimulated Mo secretion of IL-1 beta immunoreactivity. We conclude that Mo IL-1 beta and TNF-alpha production is normal in patients with recent-onset and long-standing IDDM. The interindividual differences in monokine responses may be accounted for by the diallelic human TNF-beta gene polymorphism rather than by HLA class II genes. This observation may be important for understanding the association of certain HLA haplotypes with autoimmune phenomena and disease.

Excess of maternal HLA-DR3 antigens in HLA DR3,4 positive type 1 (insulin-dependent) diabetic patients

The susceptibility determinants of Type 1 (insulin-dependent) diabetes mellitus are known to be associated with both HLA-DR3 and DR4. In our study we wished to determine if the parental origin of these antigens could influence susceptibility to the disease. We analysed the inheritance of DR3 and DR4 haplotypes from the father or mother (DR3p, DR4p, DR3m and DR4m, respectively), in the index cases and in the affected and non-affected siblings of 246 diabetic simplex and 41 multiplex families without affected parents. An independent series of 80 multiplex families (GAW 5) was also studied. Among the DR3,4 positive index cases and affected siblings, the paternal and maternal DR3 and DR4 antigens were not distributed randomly: 62% and 72%, respectively, had received DR4 from their father and DR3 from their mother (DR4p/DR3m), while only 38% and 28%, respectively, had received a paternal DR3 together with a maternal DR4 (DR3p/DR4m). This differed significantly from the 50% expected ratio (p less than 0.01) and was not observed in unaffected siblings. No excess of maternal DR3 in the absence of DR4 and no excess of paternal DR4 in the absence of DR3 were observed. The finding suggests that some maternal DR3 related event (presumably during pregnancy) might play an enhancing role in the pathogenesis of Type 1 diabetes. It also implies that siblings with both DR4p and DR3m have a significantly higher risk for disease than those with DR3p and DR4m.

HLA-DQ beta-chain restriction fragment length polymorphism as a risk marker in type 1 (insulin-dependent) diabetes mellitus: a Finnish family study

Finnish Type 1 (insulin-dependent) diabetic families were analysed for HLA-DQ beta-chain polymorphism using a short intron-specific probe. A simple hybridization pattern was obtained in which all fragments were associated significantly with Type 1 diabetes. The simultaneous presence of two different risk markers, the allelic 12-kilobase and 4-kilobase fragments were strongly associated with Type 1 diabetes since 50% of the patients had this combination compared with only 2% of the control subjects. The cosegregated 7.5/3.0 kilobase fragments, which were associated with HLA-DR2 and DRw6 were not detected among the diabetic patients but were present in 48% of the control subjects. Our results provide further support for the location of susceptibility determining factors in the HLA-DQ gene area. The clear-cut, simple restriction fragment length polymorphism pattern obtained here, which bears a resemblance to a two allelic system, therefore makes this method applicable for estimating the risk of Type 1 diabetes at the population level.

A comparison of childhood and adult type I diabetes mellitus

The incidence rate of insulin-dependent (Type I) diabetes mellitus is bimodal: one peak occurs close to puberty, and the other in the fifth decade. To evaluate possible differences in these forms of the disease, we examined the clinical, biochemical, autoimmune, and genetic features of 82 children and adolescents (1.3 to 18.2 years old) and 44 adults (20.0 to 55.8 years old) when they presented with Type I diabetes. The mean (+/- SEM) duration of symptoms before diagnosis was longer in the adults (7.5 +/- 1.0 vs. 3.9 +/- 0.4 weeks; P less than 0.001), and their serum C-peptide concentrations at diagnosis were higher (0.29 +/- 0.03 vs. 0.17 +/- 0.01 nmol per liter; P less than 0.001), suggesting that they had more residual beta-cell function. There were no significant differences between the two groups in sex ratio, blood glucose levels, hemoglobin A1 values, degree of metabolic decompensation, or frequency of Type I diabetes in first-degree relatives. Thirty-four of 80 children tested (42.5 percent) were positive for insulin autoantibodies, as compared with only 1 of 26 adults (3.8 percent; P less than 0.001). However, the frequencies of islet-cell autoantibodies were similar in the adults and children (conventional autoantibodies, both 81 percent; complement-fixing autoantibodies, 46.2 percent and 60 percent). More children than adults were heterozygous for both HLA-Dw3/4 antigens (26.6 percent vs. 9.8 percent; P less than 0.05) and HLA-DR3/4 antigens (36.6 percent vs. 12.5 percent; P less than 0.05). We conclude that Type I diabetes that begins in adulthood is characterized by a longer symptomatic period before diagnosis, better preservation of residual beta-cell function, and lower frequencies of insulin autoantibodies and HLA-D3/D4 heterozygosity than Type I diabetes that begins in childhood or adolescence.

Albuminuria reflects widespread vascular damage. The Steno hypothesis

Albuminuria in Type 1 (insulin-dependent) diabetes is not only an indication of renal disease, but a new, independent risk-marker of proliferative retinopathy and macroangiopathy. The coincidence of generalised vascular dysfunction and albuminuria, advanced mesangial expansion, proliferative retinopathy, and severe macroangiopathy suggests a common cause of albuminuria and the severe renal and extrarenal complications associated with it. Enzymes involved in the metabolism of anionic components of the extracellular matrix (e.g. heparan sulphate proteoglycan) vulnerable to hyperglycaemia, seem to constitute the primary cause of albuminuria and the associated complications. Genetic polymorphism of such enzymes is possibly the main reason for variation in susceptibility.

Genetic analysis of complex traits: insulin-dependent diabetes mellitus and affective disorders. Proceedings of a workshop. Chantilly, France, September 2-5, 1987

The present knowledge of the HLA system and its biological function is summarized as a basis for the subsequent discussion of the associations between this system and insulin-dependent diabetes (IDDM) and some mechanisms that may explain them. Although the serologically detectable DR determinants are still the most handy markers, there is now increasing evidence from studies of restriction enzyme fragment length polymorphism (RFLP) in IDDM that DQ determinants may play a primary role in causing susceptibility and/or resistance to this disease. Thus, it is now evident that about 90% of DR4-positive diabetics carry the DQw8 determinant present in only about 65% of DR4-positive controls. Most recently, it has been claimed that an aspartic acid in position 57 of the DQB1 (DQ-beta-1) chain confers resistance to IDDM. Although this may be true, it does not explain the disproportionate decrease of DR2 or the particularly high risk of DR3/4 heterozygotes, which is still good evidence that several HLA genes are involved. Because Class II antigens show the strongest associations, the most plausible hypothesis about the mechanism(s) involves specific presentation of as yet unknown antigenic peptides to T-helper lymphocytes, which may induced the formation of both anti-islet cell antibodies and T-cytotoxic lymphocytes capable of destroying beta cells. However, T-suppressor lymphocytes also may be involved. If this hypothesis is correct, the most urgent task is to define the antigenic peptides in question, whether they are environmental (e.g., viral) or autologous.

The susceptibility to insulin-dependent diabetes mellitus is associated with C4 allotypes independently of the association with HLA-DQ alleles in HLA-DR3,4 heterozygotes

In the genetically homogeneous Danish population, 27 HLA-DR3,4 heterozygous patients with insulin-dependent diabetes mellitus (IDDM) and 19 DR3,4 heterozygous controls without family history of IDDM were investigated for HLA-region markers and Gm and Km immunoglobulin allotypes. The aim was to define susceptibility factors for IDDM development other than HLA-DR using a number of techniques: lymphocytotoxicity (HLA-DR and DQ antigens), cellular methods (Dw and DP typing), restriction fragment length polymorphism (DQ alleles), electrophoresis and immunofixation (BF and C4 allotypes), and passive hemagglutination inhibition (Gm and Km immunoglobulin allotypes). The complement allotype C4A3 and the HLA-DQw8 (DQw3.2) antigen were found in all of the patients, whereas this was the case for only 8 of the 19 controls (P = 6 x 10(-6)): five lacked C4A3, five others lacked DQw8, and one of the controls lacked both of these factors. Fourteen of the patients had the complement allotype C4B3 versus three of the controls (P = 0.01). Previously reported family studies suggest that these alleles are part of the following haplotype: B15, BFS, C4A3, C4B3, DR4, Dw4, DQw8, and these factors were found together in ten of the patients versus one of the controls (P = 0.01). The markers usually associated with DR3 did not show significant differences between IDDM patients and controls, and the non-HLA markers studied showed no significant deviation from what was expected. In addition to the susceptibility factor DQw8, the study suggests the existence of susceptibility genes for IDDM near the complement C4 genes on DR4-carrying haplotypes.(ABSTRACT TRUNCATED AT 250 WORDS)

Endotoxin-stimulated human monocyte secretion of interleukin 1, tumour necrosis factor alpha, and prostaglandin E2 shows stable interindividual differences

The secretions of interleukin 1 (IL-1), tumour necrosis factor alpha (TNF), and prostaglandin E2 (PGE2) of low-dose E. coli lipopolysaccharide (LPS)-stimulated human monocytes (M phi) were investigated in an endotoxin (ET)-free milieu (less than 1.6 pg LPS/ml). Human M phi cultures from nine healthy men were stimulated with 0, 12.5-500, and 250,000 pg LPS/ml as measured by a very sensitive Limulus test. The IL-1 activity was tested by the mouse costimulatory thymocyte (LAF) assay, which was thoroughly standardized and characterized (interassay variation 22-24%, intra-assay variation 3-7%). Spontaneous M phi secretions of IL-1, TNF, and PGE2 were negligible, but 12.5 pg LPS/ml significantly stimulated the secretions of these M phi products and the monokine responses to 500 and 250,000 pg LPS/ml were almost in the same range. It was demonstrated that the secretions of IL-1-TNF and TNF-PGE2 were strongly correlated. Pronounced interindividual differences in LPS responsiveness were demonstrated, and two low-responders, one of whom was HLA-DR1,2-positive, were identified. Three first-degree relatives of the DR1,2-positive low-responder had similar low responses. Furthermore, M phi cultures were prepared weekly for 4 weeks from four HLA-DR different men and the only DR2,2 homozygous individual had low monokine responses. In conclusion, stable interindividual differences in in vitro monokine and PGE2 secretions of LPS-stimulated M phi were demonstrated. It is suggested that HLA-DR2-positive individuals may be low responders.