HLA-D region beta-chain DNA endonuclease fragments differ between HLA-DR identical healthy and insulin-dependent diabetic individuals

The KAG motif of HLA-DRB1 (β71, β74, β86) predicts seroconversion and development of type 1 diabetes

BACKGROUND

HLA-DR4, a common antigen of HLA-DRB1, has multiple subtypes that are strongly associated with risk of type 1 diabetes (T1D); however, some are risk neutral or resistant. The pathobiological mechanism of HLA-DR4 subtypes remains to be elucidated.

METHODS

We used a population-based case-control study of T1D (962 patients and 636 controls) to decipher genetic associations of HLA-DR4 subtypes and specific residues with susceptibility to T1D. Using a birth cohort of 7865 children with periodically measured islet autoantibodies (GADA, IAA or IA-2A), we proposed to validate discovered genetic associations with a totally different study design and time-to-seroconversions prior to clinical onset of T1D. A novel analytic strategy hierarchically organized the HLA-DRB1 alleles by sequence similarity and identified critical amino acid residues by minimizing local genomic architecture and higher-order interactions.

FINDINGS

Three amino acid residues of HLA-DRB1 (β71, β74, β86) were found to be predictive of T1D risk in the population-based study. The "KAG" motif, corresponding to HLA-DRB1×04:01, was most strongly associated with T1D risk ([O]dds [R]atio=3.64, p = 3.19 × 10-64). Three less frequent motifs ("EAV", OR = 2.55, p = 0.025; "RAG", OR = 1.93, p = 0.043; and "RAV", OR = 1.56, p = 0.003) were associated with T1D risk, while two motifs ("REG" and "REV") were equally protective (OR = 0.11, p = 4.23 × 10-4). In an independent birth cohort of HLA-DR3 and HLA-DR4 subjects, those having the "KAG" motif had increased risk for time-to-seroconversion (Hazard Ratio = 1.74, p = 6.51 × 10-14) after adjusting potential confounders.

INTERPRETATIONS

DNA sequence variation in HLA-DRB1 at positions β71, β74, and β86 are non-conservative (β74 A→E, β71 E vs K vs R and β86 G vs V). They result in substantial differences in peptide antigen anchor pocket preferences at p1, p4 and potentially neighboring regions such as pocket p7. Differential peptide antigen binding is likely to be affected. These sequence substitutions may account for most of the HLA-DR4 contribution to T1D risk as illustrated in two HLA-peptide model complexes of the T1D autoantigens preproinsulin and GAD65.

FUNDING

National Institute of Diabetes and Digestive and Kidney Diseases and the Swedish Child Diabetes Foundation and the Swedish Research Council.

Type 1 Diabetes: Etiology, Immunology, and Therapeutic Strategies

Type 1 diabetes (T1D) is a chronic autoimmune disease in which destruction or damaging of the beta-cells in the islets of Langerhans results in insulin deficiency and hyperglycemia. We only know for sure that autoimmunity is the predominant effector mechanism of T1D, but may not be its primary cause. T1D precipitates in genetically susceptible individuals, very likely as a result of an environmental trigger. Current genetic data point towards the following genes as susceptibility genes: HLA, insulin, PTPN22, IL2Ra, and CTLA4. Epidemiological and other studies suggest a triggering role for enteroviruses, while other microorganisms might provide protection. Efficacious prevention of T1D will require detection of the earliest events in the process. So far, autoantibodies are most widely used as serum biomarker, but T-cell readouts and metabolome studies might strengthen and bring forward diagnosis. Current preventive clinical trials mostly focus on environmental triggers. Therapeutic trials test the efficacy of antigen-specific and antigen-nonspecific immune interventions, but also include restoration of the affected beta-cell mass by islet transplantation, neogenesis and regeneration, and combinations thereof. In this comprehensive review, we explain the genetic, environmental, and immunological data underlying the prevention and intervention strategies to constrain T1D.

The regulatory role of dendritic cells in the induction and maintenance of T-cell tolerance

The induction and maintenance of T-cell tolerance to tissue antigens is essential to prevent autoimmunity. Combinations of central and peripheral mechanisms act in parallel to inactivated, eliminated or control autoreactive T cells. Both centrally and peripherally, a key requirement for self-tolerance is the presentation of self-antigens in a correct context. There is now evidence to suggest that dendritic cells (DCs) play a fundamental role in the development of central and peripheral tolerance. In this review, we summarize recent progress toward the definition of the multiple roles of DCs in these processes. We will also discuss the association between defects in the DC compartment and the development of autoimmune responses, with particular reference to DC deregulation in the context of type I diabetes.

Control of type 1 diabetes by CD4+Foxp3+ regulatory T cells: lessons from mouse models and implications for human disease

In recent years, there has been a revival of the concept of CD4(+) regulatory T (T(reg)) cells as being a central control point in various immune responses, including autoimmune responses and immunity to transplants, allergens, tumours and infectious microbes. The current literature suggests that T(reg) cells are diverse in their phenotype and mechanism(s) of action, and as such, may constitute a myriad of naturally occurring and induced T cell precursors with variable degrees of regulatory potential. In this review, we summarize research from various laboratories, including our own, showing that CD4(+)Foxp3(+) T(reg) cells are critical in the control of type 1 diabetes (T1D) in mouse models and humans. In this review, we also discuss cellular and molecular determinants that impact CD4(+)Foxp3(+) T(reg) cell development and function and consequential resistance to organ-specific autoimmune disease. Recent advances in the use of CD4(+)Foxp3(+) T(reg) cellular therapy to promote immunological tolerance in the absence of long-term generalized immunosuppression are also presented.

A case of stiff-person syndrome, type 1 diabetes, celiac disease and dermatitis herpetiformis

Antibodies against glutamic acid decarboxylase (GAD) are involved in the pathophysiology of stiff-person syndrome (SPS) and type 1 diabetes. GAD catalyses the conversion of glutamate to gamma-aminobutyric acid (GABA). GABA acts as a neurotransmitter between neurones, while in pancreatic beta cells it plays an integral role in normal insulin secretion, hence the clinical presentation of muscular spasms in SPS and insulin deficiency in diabetes. Despite this apparent major overlap in pathophysiology, SPS only rarely occurs in individuals with type 1 diabetes. We report the case of a 41-year-old man presenting with a simultaneous diagnosis of both these conditions. His case is unusual in that it is the first reported case in the literature of these conditions occurring in someone with celiac disease (CD) and dermatitis herpetiformis. We discuss why SPS and type 1 diabetes co-exist in only a minority of cases and speculate on the underlying mechanism of the association with CD and dermatitis herpetiformis in our patient.

Genetic polymorphisms in susceptibility to Type 1 Diabetes

Type 1 Diabetes is a serious complex disease caused by several environmental and genetic factors. It is one of most common childhood diseases, requires life-long treatment, and is associated with increased mortality, mainly due to complications that occur later in life. More than three decades of genetic studies have identified several genetic disease variants and a longer list of putative associated genetic loci. These findings have greatly increased our understanding of the genetic background of T1D and have encouraged the development of genetic tools for mapping complex diseases. Here we review the wealth of data on T1D and discuss the major genetic polymorphisms involved in the disease. We place some putative genetic risk factors in perspective and look at those still to be detected.

Several genes in the extended human MHC contribute to predisposition to autoimmune diseases

Autoimmune diseases, such as type 1 diabetes, rheumatoid arthritis, psoriasis and systemic lupus erythematosus, affect approximately 4% of the population in industrialized countries, and are characterized by an immune-mediated destruction of autologous cells and/or tissues. More knowledge is needed to prevent and treat this large group of diseases. Unravelling the genetic predisposing factors is important in this respect, and large research efforts have been initiated to reach this goal. The human MHC, also called the human leukocyte antigen (HLA) complex, is known to harbour major genetic determinants for autoimmune diseases. For several autoimmune diseases certain classical HLA class II and/or class I genes are strongly associated with disease. As a result of recent systematic screening studies additional genes and regions in the MHC, including the extended MHC, are now known to contribute to the predisposition.

The genetics of autoimmune endocrine disease

The common autoimmune endocrinopathies result from an interaction between environmental factors and genetic predisposition. Several chromosomal gene regions have been shown to contribute to more than one disease, supporting the clinical observation that the autoimmune endocrine diseases cluster within individuals and families. Genetic studies have implicated the major histocompatability complex (MHC)-human leucocyte antigen (HLA) genes on chromosome 6p21, although this chromosomal region does not explain all of the genetic contribution to the various disorders. Non-MHC-HLA genes, including disease-specific loci, are beginning to be identified and the publication of the draft sequence of the human genome will undoubtedly expediate future discoveries. Combined with the establishment of large cohorts of subjects with disease and the development of technology capable of performing high-throughput genotyping, genetic studies are likely to impact on the future treatment and prevention of the common autoimmune endocrine diseases.

HLA genes associated with autoimmunity and progression to disease in type 1 diabetes

Insulin dependent diabetes mellitus (type I DM) is caused by an autoimmune process which culminates in destruction of pancreatic beta cells with resultant loss of insulin production. Preceding the clinical diagnosis of type I DM is a preclinical stage characterized by autoantibodies to insulin, glutamic acid decarboxylase (GAD) and a tyrosine phosphatase-like molecule (IA-2). We have studied both HLA class I and class 2 allele distributions in diabetic probands and autoantibody positive individuals in members of 452 families recruited for the Australian type I diabetes DNA repository. The results demonstrate that progression to autoimmunity as measured by the appearance of autoantibodies is strongly associated with the class 2 alleles DRB1*03 and DRB*04 and with DRB1*03/04 heterozygosity. In contrast, the progression to clinical disease appears associated with class I alleles A24, A30 and B18 while A1, A28, B14 and B56 appear negatively associated. The class 2 alleles appear to have a minimal role in the progression from autoantibody positivity to clinical disease. These results are consistent with the view that CD4+ T cells responding to peptides in the context of class 2 molecules are responsible for initiating autoantibody production, while the destruction of islet cells leading to clinical expression of the disease is the function of CD8+ T cells recognizing relevant peptides in the context of class I molecules.

The HLA-DQB alleles and amino acid variants of the vitamin D-binding protein in diabetic patients in Alsace

BACKGROUND

The HLA-DQB1 chain, in particular the amino acid in position 57, and genetic variants of the vitamin D-binding protein (DBP) have been reported to be associated with type 1 diabetes. There are two known polymorphisms in exon 11 of the DBP gene resulting in amino acid variants: codons 416 GAT --> GAG (Asp --> Glu) and 420 ACG --> AAG (Thr --> Lys). We compared distribution of DQB1 alleles and amino acid variants of DBP in type 1 diabetic patients (n = 44) in the Alsacian population and in healthy controls (n = 58).

METHODS

The second exon of the DQB1 gene and exon 11 of DBP were analyzed by restriction mapping after polymerase chain reaction.

RESULTS

A significant enrichment in DQB1 alleles encoding for an amino acid different from Asp in position 57 (NA) was observed in diabetic subjects as compared to controls (94.3 vs. 32.8%; p < 0.001). Combinations other than Ala/Ala carried the highest relative risk (OR = 52; p < 0.001). The analysis of the polymorphism in exon 11 of DBP showed a significant difference in the allele frequency of the HaeIII site, but not of the StyI site between patients and controls. Allele frequencies of HaeIII in diabetic subjects were 36% and 64% for Asp and Glu respectively (p < 0.001; chi(2) = 29.5). The frequency of Asp/Asp and Glu/Glu genotypes was increased in controls and diabetic subjects respectively. DBP alleles in individuals carrying the DQB1 NA combination revealed that 46.6% of diabetics were DBP Asp/Glu, but this was not statistically significant using the Fisher exact test (16/31 vs. 0/3; p = 0.23).

CONCLUSIONS

The study of the DQB1 chain confirmed the value of alleles encoding for an amino acid different from Asp in position 57 (NA) in the susceptibility to type 1 diabetes. The allele frequency of the HaeIII site, but not of the StyI site, differed between patients and controls (HaeIII p < 0.001; StyI p > 0.05).

HLA complex genes in type 1 diabetes and other autoimmune diseases. Which genes are involved?

The predisposition to develop a majority of autoimmune diseases is associated with specific genes within the human leukocyte antigen (HLA) complex. However, it is frequently difficult to determine which of the many genes of the HLA complex are directly involved in the disease process. The main reasons for these difficulties are the complexity of associations where several HLA complex genes might be involved, and the strong linkage disequilibrium that exists between the genes in this complex. The latter phenomenon leads to secondary disease associations, or what has been called 'hitchhiking polymorphisms'. Here, we give an overview of the complexity of HLA associations in autoimmune disease, focusing on type 1 diabetes and trying to answer the question: how many and which HLA genes are directly involved?

Prevalence of human leukocyte antigen DQA1 and DQB1 alleles in Kuwaiti Arab children with type 1 diabetes mellitus

The prevalence of human leukocyte antigen (HLA) DQB1 and DQA1 alleles has been determined in 78 Kuwaiti Arab children with insulin-dependent diabetes mellitus (IDDM) and in 57 normal healthy controls with similar ethnic background. The typing of HLA-DQ alleles was carried out using an allele-specific DNA-based polymerase chain reaction (PCR) SSP method. DR typing was also performed in 212 control subjects using PCR-SSP (sequence specific primer) method. A significantly higher frequency of DQB1*0201 allele was found in IDDM cases compared to the controls (p<0.001). There was no significant difference in the prevalence of DQB1 alleles *0302, *0501, and *0602 between IDDM cases and the controls. In contrast, DQB1 alleles *0301, *0402, *0502, *0602, and *0603 were represented at a somewhat higher frequency in controls compared to the IDDM cohort. The frequency of DQA1 allele *0301, which encode for an Arg at codon 52, was significantly higher in the IDDM patients compared to the controls (p<0.001). The frequency of DQA1 allele *0302 was also higher in IDDM cases than controls (p = 0.034) but the difference was less pronounced than DQA1*0301. Amongst the Arg52 alleles, no significant difference was detected in the frequency of *0401 between IDDM cases and the controls and the allele *0501 was detected only in controls. For non-Arg52 alleles *0103, *0104, and *0201, the differences in the two groups were not significant, with the exception of allele *0104 (p = 0.024). DR3 was the most common type in the Kuwaiti general population (28%) and DRB1*0301 was detected in 41% of the individuals with DR3 specificity. Analysis of HLA-DQBI/DQA1 haplotypes from IDDM cases and controls revealed a significantly high frequency of haplotype DQA1*0301/DQB1*0201 between Kuwaiti IDDM cases (49/78, 63%) and the controls (8/57, 14%).

The influence of age at onset and gender on the HLA-DQA1, DQB1 association in Chinese children with insulin dependent diabetes mellitus

Certain alleles of human leukocyte antigen (HLA)-DR and -DQ genes have been strongly associated with susceptibility and resistance to insulin- dependent diabetes mellitus (IDDM). To further clarify the association of HLA DQ alleles with IDDM and the influence of age at onset and gender on the association with IDDM, we investigated the association of HLA-DQA1, -DQB1 in 54 childhood onset Chinese (21 male) IDDM patients and 65 normal controls by using polymerase chain reaction-sequence specific primer (PCR-SSP). The mean age plus or minus SD at onset of IDDM patients was 8.37+/-3.54 year old. Our results revealed that the frequencies of DQA1 *0301, *0302, DQB1 *0201, and *0302 in IDDM patients were significantly higher than that in the control group (p < 0.025, < 0.005, < 0.001, and < 0.001, respectively). The frequency of DQA1 *0301, *0302, DQB1 *0201, and *0302 were susceptible alleles to IDDM with relative risks of 2.0, 3.5, 5.0 and 4.3, respectively. The protective alleles to IDDM were DQA1 *0101, *0103, DQB1 *0301, *0503, and *0602. We divided IDDM patients into three groups according to age at onset (1-5, 6-10, and 11-15 years old). The frequency of DQA1 *0302 decreased as age increased, and the frequency of DQA1 *0501 increased as age increased. Our results also showed that male IDDM patients had higher frequencies of DQA *0501, DQB1 *0201 than female IDDM patients (p < 0.025 and < 0.025, respectively), while female IDDM patients had higher frequencies of DQB1 *0502 than male IDDM patients (p < 0.05). In our study significant susceptibility haplotypes to IDDM were DQA1 *0301-DQB1 *0302, DQA1 *0501-DQB1 *0201, DQA1 *0301-DQB1 *0201, and DQA *0302-DQB1 *0201.

Complex interaction between HLA DR and DQ in conferring risk for childhood type 1 diabetes

Type 1 (insulin-dependent) diabetes mellitus is associated with HLA DR and DQ factors, but the primary risk alleles are difficult to identify because recombination events are rare in the DQ-DR region. The risk of HLA genotypes for type 1 diabetes was therefore studied in more than 420 incident new onset, population-based type 1 diabetes children and 340 age, sex and geographically matched controls from Sweden. A stepwise approach was used to analyse risk by relative and absolute risks, stratification analysis and the predispositional allele test. The strongest relative and absolute risks were observed for DQB1*02-DQA1*0501/DQB1*0302-DQA1*0301 heterozygotes (AR 1/46, P < 0.001) or the simultaneous presence of both DRB1*03 and DQB1*0302 (AR 1/52, P < 0.001). Stratification analysis showed that DQB1*0302 was more frequent among DRB1*04 patients than DRB1*04 controls (P < 0.001), while DRB1*03 was more frequent among both DQA1*0501 (P < 0.001) and DQB1*02 (P < 0.001) patients than respective controls. The predispositional allele test indicated that DRB1*03 (P < 0.001) would be the predominant risk factor on the DRB1*03-DQA1*0501-DQB1*02 haplotype. In contrast, although DQB1*0302 (P < 0.001) would be the predominant risk factor on the DRB1*04-DQA1*0301-DQB1*0302 haplotype, the predispositional allele test also showed that DRB1*0401, but no other DRB1*04 subtype, had an additive risk to that of DQB1*0302 (P < 0.002). It is concluded that the association between type 1 diabetes and HLA is due to a complex interaction between DR and DQ since (1) DRB1*03 was more strongly associated with the disease than DQA1*0501-DQB1*02 and (2) DRB1*0401 had an additive effect to DQB1*0302. The data from this population-based investigation suggest an independent role of DR in the risk of developing type 1 diabetes, perhaps by providing diseases-promoting transcomplementation molecules.

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 associations in insulin-dependent diabetes mellitus: no independent association to particular DP genes

Genes in the HLA complex are associated with susceptibility to develop insulin-dependent diabetes mellitus (IDDM). Several studies, from different populations, have demonstrated strong associations between particular DR and DQ alleles and disease susceptibility or protection. Whether also particular DP alleles may independently contribute is more controversial. Some studies have found a greater frequency of DPB1*0301 among IDDM patients compared to controls, apparently independently of linkage disequilibrium with high risk DR and DQ alleles. To address this question in an ethnically homogeneous population (Norwegian), we have DPA1 and DPB1 genotyped 237 IDDM patients and 287 DRB1-DQA1-DQB1 matched controls, carrying high risk DR3/4 or DR4/4 genotypes. We were unable to detect any significant independent associations between DP alleles and IDDM susceptibility or protection in this population. Thus, our results do not support previous reports on an independent association between some DP alleles and susceptibility to develop IDDM.

Distribution of HLA class II alleles and haplotypes in insulin-dependent Moroccan diabetics

HLA class II polymorphism in Moroccan IDDM patients has not been investigated so far. In this study, HLA-DRB1, -DQA1, and -DQB1 allele and haplotype frequencies were analyzed in 125 unrelated Moroccan IDDM patients and 93 unrelated healthy controls, all originating from the Souss region and mostly of Berber origin. Some common features with other Caucasian groups were observed, in particular, a predisposing effect of the DRB1*03-DQA1*0501-DQB1*0201 and DRB1*04-DQA1*0301-DQB1*0302 alleles or allelic combinations. The Moroccan IDDM group also presented with more specific characteristics. Among DRB1*04 subtypes, DRB1*0405 was associated with susceptibility to and DRB1*0406 with protection from the disease. The haplotype and the relative predispositional effect (RPE) analyses indicated that the DRB1*08-DQA1*0401-DQB1*0402 haplotype was also associated with susceptibility to IDDM. Interestingly, the DRB1*09-DQA1*0301-DQB1*0201 haplotype, completely absent from the control group and very rare in North African populations, was observed in 7.2% of the Moroccan diabetics. Conversely, the DRB1*07-DQA1*0201-DQB1*0201 and DRB1*15-DQA1*0102-DQB1*0602 haplotypes were associated with protection from IDDM. Finally, we observed an age-dependent genetic heterogeneity of IDDM, the frequencies of predisposing alleles being higher and those of protective alleles lower in childhood- than in adult-onset diabetics. Our data on Moroccan diabetics, together with data on European and Northern Mediterranean patients, suggest a gradient of various HLA class II predisposing and protective markers that link these populations.

Different contribution of HLA-DR and -DQ genes in susceptibility and resistance to insulin-dependent diabetes mellitus (IDDM)

Previous studies have indicated that certain alleles of HLA-DR and -DQ genes were strongly associated with susceptibility and resistance to insulin-dependent diabetes mellitus (IDDM), and the role of DQ molecule in IDDM has been suggested. To further clarify the association of DQ alleles with IDDM, we determined the nucleotide sequences of full-length cDNA from 13 DQA1 alleles and 14 DQB1 alleles. The sequencing analysis revealed sequence polymorphisms outside the hypervariable region of DQ genes. We then analyzed the DQA1 and DQB1 polymorphisms along with that of DRB genes in 86 B-lymphoblastoid cell lines (B-LCLs) from various ethnic groups and in healthy unrelated Japanese and Norwegian individuals. The allelic and haplotypic distributions in each population revealed the characteristic haplotypic formation in the HLA class II region. HLA genes in 139 Japanese and 100 Norwegian IDDM patients were analyzed. DQB1*0301 was negatively associated with IDDM in both ethnic groups, irrespective of associated DRB1 and DQA1 alleles. In DQB1*0302 positive populations, which represented a positive association with IDDM in both ethnic groups, DRB1*0401, *0404, *0802 haplotypes increased in the patients, whereas DRB1*0406 haplotype decreased. Considering about the hierarchy in DRB1 alleles with IDDM susceptibility (DRB1*0401>*0404>*0403 in Norwegian and DRB1*0802>*0403>*0406 in Japanese), the genetic predisposition to IDDM is suggested to be defined by the combination of DR-associated susceptibility and DQ-associated susceptibility and by the DQ-associated resistance which is a dominant genetic trait.

Polymorphic structural features of modelled HLA-DQ molecules segregate according to susceptibility or resistance to IDDM

The structural features of HLA-DQ alleles which are susceptible and resistant to insulin-dependent diabetes mellitus (IDDM) have been examined using a model of their three-dimensional structure obtained by energy minimisation, based on the published structure of HLA-DR1. The model shows DQ molecules to have an overall shape nearly identical to that of DR molecules, but with significant differences in the fine structure: 1) the antigen-binding groove of DQ molecules has a polymorphic first pocket; this pocket can be either amphiphilic or hydrophilic, 2) The beta 49-56 dimerisation domain of DQ is polymorphic: hydrophobic, or amphiphilic, or hydrophilic and positively charged, leading to spontaneous or T-cell receptor-induced homodimer formation, or T-cell receptor-induced homodimer formation, or difficulty of the formation of such dimers, respectively; 3) a prominent Arg-Gly-Asp loop is formed by some DQ alleles (beta 167-169) and probably functions in cell adhesion. There are also small differences in the residues and sequences implicated in CD4 binding (mostly in DQ beta 134-148) but the significance of these differences cannot be evaluated at present. All seven DQ alleles which confer susceptibility to IDDM possess a hydrophilic first pocket in the antigen-binding groove, a hydrophobic or amphiphilic beta 49-56 dimerisation patch that allows for spontaneous or T-cell receptor-induced dimerisation, and the Arg-Gly-Asp loop. By contrast, in the protective alleles at least one of these three features is absent. This segregation of phenotypes according to susceptibility or resistance can well explain the model of tighter autoantigen binding by the protective alleles compared to the susceptible alleles, previously proposed for the pathogenesis of IDDM.

Spatial clustering in childhood diabetes: evidence of an environmental cause

If environmental factors are important in the aetiology of insulin-dependent (Type 1) diabetes mellitus, primary schooling would be more likely to be shared by cases in an epidemic year compared with controls. We have examined a case control study, comparing primary schools attended. Cases were identified from an established register with known accurate ascertainment and compared with controls taken from a central register of all children and date of birth, sex, and race matched. Parents were asked to complete a structured questionnaire which included questions relating to the child's schooling. There were 187 cases with at least a first matched control. Thirty-two of the cases attended the same nursery or primary school as another case, 18 in the same academic year, compared with 12 controls attending the same school as another control (99% confidence interval (CI) for the difference between proportions 0.0572 - 0.107). Of these cases diagnosed in 1986, 9 attended the same school as another case. Spatial clustering occurs in Type 1 diabetes. This is further evidence of an environmental factor contributing to the genesis of the disease.

The minisatellite in the diabetes susceptibility locus IDDM2 regulates insulin transcription

Genetic susceptibility to insulin-dependent diabetes mellitus (IDDM) is inherited as a polygenic trait. One of the loci implicated in IDDM is a polymorphic minisatellite 5' of the human insulin (INS) gene on chromosome 11. This insulin-linked polymorphic region (ILPR) is composed of tandemly repeated sequences, which fall into three size classes: IDDM is strongly associated with short ILPR alleles. We now show that the ILPR is capable of transducing a transcriptional signal in pancreatic beta-cells, with a long ILPR possessing greater activity than a short ILPR. The ILPR contains numerous high-affinity binding sites for the transcription factor Pur-1, and transcriptional activation by Pur-1 is modulated by naturally occurring sequences in the ILPR. Our results demonstrate a possible function for this unique minisatellite, which may have implications for type 1 diabetes.

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)

Effect of genetic risk load defined by HLA-DQB1 polymorphism on clinical characteristics of IDDM in children

Clinical and autoimmune characteristics of 150 diabetic children of mean age 7.8 years (SD 4.1 years) were recorded at clinical manifestation and during the first 2 years of IDDM in order to investigate whether subjects with high risk HLA-DQB1 genotypes differ from those without these risk markers. When comparing subjects with the DQB1*0302/0201, DQB1*0302/x, DQB1*0201/x, or other DQB1 genotypes (x = no protective allele), no differences were found in the age of the subjects at diagnosis, the duration of hyperglycaemic symptoms, or the length of clinical remission. The frequency of islet cell antibodies (ICA) and quantitative serum levels of these antibodies were of the same magnitude in all four groups. During the initial 2 years of IDDM serum C-peptide concentrations were observed to be inversely related to the degree of genetic risk (P < 0.001 in two-way analysis of variance for repeated measures), the lowest C-peptide levels being observed in the group of DQB1*0302/0201 heterozygotes (P < 0.001 vs. DQB1*0201/x; P < 0.01 vs. DQB1*0302/x; P = 0.05 vs. others). On the other hand, the subjects with the DQB1*0201 genotype had the highest serum C-peptide concentrations, the levels being even higher than those of the patients carrying neutral or protective DQB1 genotypes (P < 0.01). These subjects also had lower daily insulin doses and blood glycated haemoglobin A1 (HbA1) levels over the initial 2 years of the disease when compared with the DQB1*0302/0201 heterozygotes (P < 0.05 and P < 0.01, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Pathogenesis of insulin-dependent diabetes mellitus

Insulin-dependent diabetes mellitus is strongly associated with certain HLA types and the presence of islet cell-specific autoantibodies. The pathogenesis is a specific loss of pancreatic beta cells. The dissection of IDDM genes is complicated by the low recurrence rate of the disease among first-degree relatives. HLA-DQ2 and 8 are closest to IDDM with a marked synergistic effect of DQ2/8 heterozygotes. The associations with other HLA genes are often explained by linkage disequilibrium. Genetic factors on other chromosomes which influence the pathogenesis are still to be fully identified but candidates are on chromosomes 11 (insulin gene polymorphisms) and 7 (TCR gene polymorphisms). The autoreactivity against the GAD65 isoform is pronounced both before and at the clinical onset of IDDM. GAD65 autoantibodies show the highest predictive value and may represent an initiating autoantigen. Autoantibodies to numerous other beta cell autoantigens are detected at the clinical onset but may represent a secondary response and antigen spreading during a sustained autoimmune attack on the beta cells. The role of T cells in human IDDM is yet to be defined. GAD65 and other islet autoantibodies have a low positive predictive value for IDDM and further investigations are needed to clarify ways to predict IDDM in the general population.

Molecular biology of IDDM

The clinical onset of insulin-dependent diabetes is associated with several autoimmune phenomena including islet cell antibodies, glutamic acid decarboxylase (the GAD65 isoform) autoantibodies (GAD65Ab) as well as insulin autoantibodies. The molecular cloning of these autoantigens has permitted the development of precise and reproducible antibody immunoassays to identify marker-positive patients and control subjects. Among patients with new-onset diabetes about 70% were GAD65Ab positive compared to 1.5% among control subjects while 46% of patients had IAA compared to 1% among control subjects. The autoreactive sites or epitopes of GAD65 and insulin remain to be determined. The disease association with HLA on chromosome 6 may help to define the epitope specificity of the autoimmune reaction. Recent data suggest that 95% of new-onset IDDM children (0-15 years of age) are positive for either DQ2, DQ8 or both compared to about 50% of healthy control subjects. HLA-DQ6 is negatively associated with the disease. Both HLA-DQ2 and DQ8 therefore seem to be necessary, but not sufficient for diabetes. Molecular modelling suggests comparable physicochemical properties of DQ2 and DQ8 but are widely different from DQ6. In 1984, the conclusion was that molecular cloning of the genes for the autoantigens, antibodies, T-cell receptors, as well as HLA class I and II molecules associated with diabetes are essential for analysing the components which control the development of pancreatic beta-cell autoimmunity. In 1994, autoantigens and HLA molecules have been cloned and recombinant reagents developed to be used in experiments aimed at testing whether it will be possible to predict IDDM.(ABSTRACT TRUNCATED AT 250 WORDS)

Unique intronic variations of HLA-DQ beta gene in early-onset periodontitis

Human leukocyte antigen (HLA) class II beta chain plays an important role in the recognition of foreign antigens in immune reactions. Different forms of immune reaction may be concerned with initiation and progression of infectious diseases such as periodontitis. In this study we examined the frequency of HLA class II serotype and the variation of HLA class II beta gene in periodontitis patients. HLA serotypic frequencies in 70 Japanese patients with periodontitis and 26 individuals with periodontal health were examined. No HLA serotype specific to any type of periodontitis was observed. In order to detect differences among some HLA serotypes, restriction fragment length polymorphism (RFLP) analysis was undertaken with cDNA probes for HLA-DR beta and HLA-DQ beta genes in 20 subjects (15 patients and 5 healthy individuals). Atypical BamHI and EcoRI restriction sites were found in the HLA-DQ beta gene from 3 patients with early-onset periodontitis. In addition to these 20 subjects, an additional 80 subjects (40 patients and 40 healthy individuals) were screened for the atypical BamHI restriction site using the polymerase chain reaction method. It was detected in 7 patients with early-onset periodontitis, 1 patient with adult periodontitis, and 3 healthy subjects. No clinical differences except age were found between patients with this gene variation and other patients. Interestingly, all 3 healthy subjects with this gene variation were from subjects whose family members developed early-onset periodontitis with the gene variation. Atypical BamHI and EcoRI restriction sites and 41-nt repeated sequence were found in the intron before the third exon of HLA-DQB gene. These results suggest that these intronic gene variations may be useful as gene markers for a subpopulation of early-onset periodontitis and might affect immune reactions such as antigen recognition.

Additive susceptibility to insulin-dependent diabetes conferred by HLA-DQB1 and insulin genes

Several genomic polymorphisms at the insulin (INS) gene and its flanking regions were analyzed in 197 unrelated Caucasian patients affected by insulin-dependent diabetes (IDDM) and 159 ethnically matched, normal controls ascertained from the South-Eastern United States. We found that the frequency of homozygotes for the common variant at the insulin gene was significantly increased in the diabetic population (RR = 2.0, p < 0.005). However, the polymorphisms in the 5' and 3' regions flanking the INS were not significantly associated with IDDM. These results suggest that the IDDM susceptibility locus on chromosome 11p is located within the region extending from the 5' VNTR to the 3' end of the INS gene. We determined the HLA-DQB1 genotypes by denaturing gradient gel electrophoresis (DGGE) and/or sequence-specific primers (SSP) techniques to assess the possible interactions between INS and HLA. DQB1*0302 had the strongest predisposing effect on IDDM susceptibility (RR = 9.3) and DQB1*0602 the strongest protective effect (RR = 0.02). However, a significant predisposing effect of DQB1*0201 could be demonstrated only after removal of the effects of DQB1*0302 and DQB1*0602. Analyses of the genotypes revealed that all genotypes containing 0602 were protective and that the heterozygous genotype 0201/0302 and homozygous genotype 0302/0302 confer the highest risk (RR = 20.9 and 12.9 respectively). However, heterozygous genotypes 0302/X (X excludes 0201, 0302 and 0602) have a significantly lower predisposing risk. Similarly, there is heterogeneity in risk between predisposing 0201/0201 homozygous individuals and protective 0201/X individuals. When subjects were stratified by HLA genotypes, the relative risks conferred by INS did not vary, thus suggesting that the susceptibility effects conferred by HLA and INS are additive rather than interactive.

TAP1 alleles in insulin-dependent diabetes mellitus: a newly defined centromeric boundary of disease susceptibility

It has been previously demonstrated that individuals with certain DR alleles have an increased relative risk of developing insulin-dependent diabetes mellitus (IDDM). The disease association is even stronger with certain DQ alleles but there is little association with DP providing a boundary of disease association to the 430 kb between DQ and DP. The recently described TAP (transporter associated with antigen processing) genes have been mapped approximately midway between DP and DQ. Therefore, it was of interest to determine if any TAP alleles were associated with IDDM. In addition to the alleles of TAP1 that have been described, others were identified during this study. Diabetics and normal controls were screened for TAP1 using single-stranded conformational polymorphism and relative risk was determined. In the same population group we have studied extensively in the past, we found a higher association of a TAP1 allele with IDDM than with any single HLA-DP allele but the risk was lower than with HLA-DQB1*0302. These data provide new limits for IDDM susceptibility to the 190-kb interval between TAP1 and HLA-DQB1.

Rapid HLA typing by multiplex amplification refractory mutation system

AIMS

To detect HLA susceptibility and protective alleles associated with insulin dependent diabetes mellitus (IDDM) using a multiplex amplification refractory mutation system (ARMS). These include DR3 and DR4 alleles at the DRB1 locus, presence or absence of aspartic acid at position 57 (Asp-57) of the DQB1 locus, and presence or absence of arginine at position 52 (Arg-52) of the DQA1 locus.

METHODS

The ARMS approach was used to design allele specific primers for the detection of the major susceptibility and protective alleles for IDDM. These include DR3 and DR4 alleles at the DRB1 locus, Asp-57 and non-Asp-57 at the DQB1 locus, and Arg-52 and non-Arg-52 alleles at the DQA1 locus. The allele specificity of each set of primers was first tested separately using DNA samples from 15 individuals previously typed for the DRB1, DQB1, and DQA1 loci using the sequence specific oligonucleotide (SSO) technique. The possibility of using multiplex ARMS for typing multiple susceptibility/protective alleles for IDDM was further investigated by testing various combinations of allele specific primers, thereby reducing the number of separate polymerase chain reactions required to type all these alleles.

RESULTS

A "three-tube" system worked well and gave accurate results. Tube 1 contained ARMS primers for the detection of IDDM susceptibility alleles DR3 and DR4; tube 2 contained ARMS primers for the detection of susceptibility alleles non-Asp-57 and Arg-52; and tube 3 contained ARMS primers for the detection of the protective alleles Asp-57 and non-Arg-52. DNA samples typed with this ARMS method were in complete agreement with those obtained using the SSO technique.

CONCLUSION

This method is rapid and has no requirement for radioactivity. It is an efficient method for population screening.

Particular HLA-DQ molecules play a dominant role in determining susceptibility or resistance to type 1 (insulin-dependent) diabetes mellitus

Genes in the HLA complex are by far the most important in determining genetic predisposition or resistance to Type 1 (insulin-dependent) diabetes mellitus. In this review evidence is presented that the HLA genes mainly involved are those encoding some particular HLA-DQ molecules. Both among Black, Caucasian and Japanese subjects particular cis or trans encoded DQ molecules are significantly associated with susceptibility, while others are associated with resistance. A varying degree of susceptibility or resistance seems to be conferred by these DQ molecules, where those determining resistance are dominant over those determining susceptibility. The degree of genetic predisposition to develop Type 1 diabetes carried by an individual would therefore be the result of his or her particular combination of DQ molecules. A primary association to particular DQ molecules explains previously found associations to other HLA complex genes by linkage disequilibrium. Some mechanisms by which particular DQ molecules may determine susceptibility or resistance are also discussed. Potential islet beta-cell reactive CD4+ T-cells may escape negative selection (deletion) in the thymus, but normally become anergized or remain ignorant extra-thymically. However, under particular circumstances they may be triggered. The DQ molecules associated with Type 1 diabetes susceptibility may preferentially bind and present triggering and/or beta-cell derived peptides to such T cells, causing beta-cell destruction. The finding that particular DQ molecules determine susceptibility may lead to new methods of preventing development of Type 1 diabetes in susceptible individuals.

Different dose effect of HLA-DQ alpha beta heterodimers in insulin-dependent diabetes mellitus and celiac disease susceptibility

To compare the quantitative effect of the DQ alpha beta heterodimers DQ alpha 52 Arg+, beta 57 Asp- and DQ alpha 1*0501, beta 1*0201 on susceptibility to IDDM and CD, we characterized, at the genomic level, the DQ alpha 52 and DQ beta 57 residues of 50 IDDM Italian patients observed in Rome. The results were compared with those of a previous study concerning the oligotyping of DQ dimers in a group of CD children belonging to the same population. Our data confirm that both diseases are primarily associated with HLA-DQ alpha beta heterodimers, but the distributions of the respective susceptible DQA1 and DQB1 alleles in the two diseases were different. In fact, the highest risk of IDDM is for subjects alpha SS, beta SS that could express, by either cis- or trans-association, four susceptible heterodimers and decreases in proportion to the number of these; in regard to CD, the highest risk was found for individuals who carried only one predisposing heterodimer.

A negative association of schizophrenia with an allele of the HLA DQB1 gene among African-Americans

Using polymorphisms of the human leukocyte antigen (HLA) DQB1 gene, a case-control study was conducted in a group of patients with schizophrenia (DSM-III, n = 58) and psychiatrically normal controls matched for ethnicity (n = 72), living in the same geographical area. A significant negative association of allele HLA DQB1*0602 with schizophrenia was present among African-Americans (odds ratio 0.19), but could not be detected in Caucasians.

HLA-DQ beta 57 in Hispanic patients with insulin-dependent diabetes mellitus

OBJECTIVE

The purpose of our study was to investigate the distribution of HLA-DQ beta-chain amino acid residue 57 (HLA-DQ beta 57) as a genetic marker of susceptibility for insulin-dependent diabetes mellitus in the Hispanic population.

STUDY DESIGN

Fifteen patients of Puerto Rican descent with juvenile-onset insulin-dependent diabetes mellitus underwent human leukocyte antigen typing for HLA-DQ beta 57 by polymerase chain reaction amplification of the target genomic DQ sequence followed by hybridization of the polymerase chain reaction product to phosphorus 32-labeled allele-specific oligonucleotide probes. A control group of 44 Hispanic adults without diabetes who were undergoing human leukocyte antigen typing for tissue donation were concurrently typed for comparison.

RESULTS

The Hispanic insulin-dependent diabetes mellitus group showed a significant increase in homozygosity for a non-aspartate amino acid (p = 0.023) over a control group of Hispanic subjects without diabetes. A high rate of heterozygosity for aspartate (53.3%) is found in Hispanic subjects with insulin-dependent diabetes mellitus as well.

CONCLUSIONS

HLA-DQ beta 57 in the Hispanic population has a distribution distinct from HLA-DQ beta 57 in the Caucasian population. A single aspartate is not protective against insulin-dependent diabetes mellitus in Hispanic subjects.

Age-dependent HLA genetic heterogeneity of type 1 insulin-dependent diabetes mellitus

The association of insulin-dependent diabetes mellitus (IDDM) with certain HLA alleles is well documented in pediatric patients. Whether a similar association is found in adult-on-set IDDM is not clear, although the disease occurs after the age of 20 in 50% of cases. HLA class II DRB1, DQA1, and DQB1 alleles were studied in 402 type I diabetics and 405 healthy controls (all Caucasian) using oligonucleotide typing after gene amplification. Alleles DRB1*03, DRB1*04, DQB1*0201, DQB1*0302, DQA1*0301, and DQA1*0501 were indeed enriched in diabetics and the highest relative risk was observed in patients carrying both the DRB1*03-DQB1*0201 and the DRB1*0402 or DRB1*0405-DQB1*0302 haplotypes. However none of these alleles, or specific residues, could alone account for the susceptibility to IDDM. Furthermore, there were major differences in HLA class II gene profiles according to the age of onset. Patients with onset after 15 yr (n = 290) showed a significantly higher percentage of non-DR3/non-DR4 genotypes than those with childhood onset (n = 112) and a lower percentage of DR3/4 genotypes. These non-DR3/non-DR4 patients, although presenting clinically as IDDM type 1 patients, showed a lower frequency of islet cell antibodies at diagnosis and a significantly milder initial insulin deficiency. These subjects probably represent a particular subset of IDDM patients in whom frequency increases with age. The data confirm the genetic heterogeneity of IDDM and call for caution in extrapolating to adult patients the genetic concepts derived from childhood IDDM.

DQA1 and DQB1 heterodimers in insulin-dependent diabetes mellitus: a genetic-epidemiological study in Finland. DiMe Study Group

Susceptibility to insulin-dependent diabetes mellitus (IDDM) correlates with the absence of aspartic acid in position 57 of the DQB1 and/or the presence of arginine in position 52 of the DQA1. It has been postulated that transcomplementation between the DQ alpha and beta chains of the two haplotypes could create new molecules conferring susceptibility to IDDM. Finland has the highest incidence of IDDM in the world (35/100,000). In a nationwide study of IDDM in childhood (DiMe study) HLA genotyping using conventional serology was carried out according to genetic-epidemiological principles. We simulated DQA1 and DQB1 alleles in 707 consecutively diagnosed IDDM probands and 98 non-diabetic children based on serology, restriction fragment length polymorphism results and sequence data assuming no recombination between DQ and DR. In 34% of Finnish children with IDDM all four combinations (two in cis and two in trans) could lead to SS heterodimers. Two-thirds of these combinations were explained by DR3,DR4 heterozygotes. In 50% of IDDM children half and in 11% a quarter of the combinations could lead to heterodimers. In 38 IDDM patients (5%) the formation of hybrid molecules was not possible. In 59% of the controls SS heterodimers were possible and should therefore have an underlying genetic susceptible for IDDM assuming the theory of transcomplementation is correct. These findings, together with the fact that the lowest frequency of DR3,DR4 heterozygosity (21%) was seen in Finland, show that heterozygosity for DQ and DR cannot explain the differences seen in IDDM incidence.

HLA class II molecules and autoimmune hepatitis susceptibility in Japanese patients

To investigate the association between autoimmune hepatitis and HLA alleles in Japanese patients, serological typing and class II genotyping were performed using the polymerase chain reaction-restriction fragment length polymorphisms (PCR-RFLP) method. Serological typing showed that HLA-B54, -DR4, -DR53, and -DQ4 were significantly more frequent in patients with autoimmune hepatitis than in controls. HLA-DR4 was most frequently associated with autoimmune hepatitis (88.7%). In PCR-RFLP typing, the frequency of DRB1*0405 was significantly higher in autoimmune hepatitis than in controls. However, there was no significant difference in the frequency of Dw between the patients and the controls who were DR4-positive. The significant increase observed in DQA1*0301 and DQB1*0401 was explained by a linkage disequilibrium with DR4. Six DR4-negative patients had DR2, but there was no significant difference in the frequency of the DR2-associated Dw-alleles compared with the DR2-positive controls. No DPB1 allele was significantly associated with autoimmune hepatitis. These findings suggest that the basic amino acid at position 13, which is present only on the DR2 and DR4 B1 molecules (Arg on DR2 and His on DR4), contributes to the susceptibility to autoimmune hepatitis among the Japanese.

Analysis of HLA genotypes and susceptibility to insulin-dependent diabetes mellitus: HLA-DQ alpha complements HLA-DQ beta

It is well known that certain genes in the HLA-D region confer increased susceptibility to insulin-dependent diabetes mellitus (IDDM). Previous studies have documented an increased risk associated with the HLA-DR beta chain alleles, DR3 and DR4, and the DQ beta chain allele DQB1*0302 (formerly DQw8). Since DQ alpha is also polymorphic and has been strongly implicated as the primary IDDM susceptibility locus in other races, we wanted to assess the contribution of DQ alpha to IDDM in Caucasians. This information would enable us to define more precisely the class II association with IDDM as well as gain insight into issues of cis versus trans association of DQ heterodimers in this disease. To this end, the DQ alpha genotype was determined for a large group of diabetic and normal Caucasian individuals who had been HLA-DQ beta and HLA-DR typed previously. Using the polymerase chain reaction and a set of twelve oligonucleotide probes, we determined the DQ alpha genotype of 323 patients with IDDM and 182 normal subjects. We found that certain DQ alpha alleles are decreased in the diabetic population compared with normal subjects (i.e. DQA1*0102 and *0103), while others are significantly increased in patients with IDDM (i.e. DQA1*0301 and *0501). In addition, certain combinations of DQ alpha alleles are associated with increased susceptibility to disease (i.e. DQA1*0301, *0501). These results parallel our findings at the DQ beta locus; however, because of the various associations between DQ alpha and DQ beta chains, the risks conferred by DQ alpha are generally lower than those at DQ beta. Moreover, our data indicate that, in Caucasians, no single DQ alpha allele accounts for the highest degree of susceptibility to IDDM as in other races, although DQ alpha analysis may be informative in a few cases. When done in combination, however, oligonucleotide analyses at both DQ alpha and DQ beta complement each other and provide a more complete assessment of the HLA-associated component of disease susceptibility in IDDM.

Analysis of HLA genotypes and susceptibility to insulin-dependent diabetes mellitus: association maps telomeric to HLA-DP

There is convincing evidence that certain combinations of alleles within the human leucocyte antigen (HLA) complex, particularly within HLA-DQ, are associated with either resistance or susceptibility to insulin-dependent diabetes mellitus (IDDM). A previous study conducted on a large, well-defined group of patients demonstrated that DQB1*0302 (DQw8) conferred 'dominant susceptibility' to IDDM while DQB1*0602 (DQw1.2) conferred 'dominant protection'. The availability of this population enabled us to further assess susceptibility associated with other class II alleles in an effort to map an outside HLA boundary of disease association. Using a group-specific polymerase chain reaction protocol and a series of oligonucleotide probes which define over twenty DP beta alleles, we studied 286 unrelated Caucasian patients with IDDM and 184 normal subjects. We found that while several alleles are increased (DPB1*0201, DPB1*0301, DPB1*0402) or decreased (DPB1*0101, DPB1*0202) in the diabetic population compared with the normal subjects, the HLA association with IDDM is considerably weaker at the DP locus. These data define the centromeric boundary for the HLA-associated susceptibility gene in IDDM, localizing susceptibility to the region telomeric to HLA-DP up to and including HLA-DQ.

Extensive study of DRB, DQA, and DQB gene polymorphism in 23 DR2-positive, insulin-dependent diabetes mellitus patients

To gain insight into the HLA subregions involved in protection against insulin-dependent diabetes mellitus (IDDM) we investigated the polymorphism of HLA-DR and -DQ genes in 23 DR2 IDDM patients. Results show the following. (1) Fourteen patients (61%) possess the DRB1, DRB5, and DQB1 alleles found in DRw16/DQw5 healthy people. These data contrast with the 5% of DRw16 normally found in DR2 populations and are in agreement with former observations supporting that the DRw16 haplotype is not protective. (2) Nine DR2 patients, i.e., 39% versus 95% in published DR2 controls, possess the DRB alleles found in DRw15 unaffected people. Among them, six patients have also DQA1 and DQB1 alleles identical to those found in DRw15/DQw6 healthy individuals. These data confirm that the DRw15/DQw6 haplotype is protective but indicate that none of the DR or DQ alleles, alone or in association, confers an absolute protection. (3) Our most striking results concern the very high frequency of recombinant haplotypes among the DRw15 patients: 3 of 9. In these three patients recombinations led to the elimination of both DQB1 and DQA1 alleles usually associated with DRw15. This strongly suggests that the occurrence of IDDM in these DRw15 patients is due to the absence of the usual DQ product and thus reinforces the assumption that DQ rather than DR region is involved in the protection conferred by the DRw15/DQw6 haplotype. Finally, analysis of the non-DRw15 haplotypes in heterozygous patients showed that IDDM can occur in the absence of any DQ alpha beta heterodimer of susceptibility.

HLA haplotypes in type 1 (insulin-dependent) diabetes mellitus: molecular analysis of the HLA-DQ locus. The DIME Study Group

In Caucasians the predisposition to Type 1 (insulin-dependent) diabetes mellitus has been shown to associate with HLA-DR3,DQw2 and DR4,DQw8 and with the presence of amino acids other than aspartic acid at position 57 on the HLA-DQ beta chain. In Finland the haplotype-specific absolute risk for developing Type 1 diabetes differs between various DR3 and DR4 positive haplotypes. The aim of our present analysis was to find out whether this variation is attributable to polymorphism at the DQ locus. As part of a nationwide prospective study including 757 serologically HLA genotyped families, we determined HLA-DQ alpha and DQ beta restriction fragment polymorphisms in 17 selected families with important susceptibility haplotypes. Additionally, the DQA1 alleles were determined from 19 haplotypes using sequence-specific oligonucleotide probes, and the DQB1 second exon was sequenced from nine haplotypes. The DR3 as well as DR4 positive haplotypes frequently found in Type 1 diabetic patients showed no variation at the HLA-DQ locus, and they were DQw2 and DQw8, respectively. The absolute risk for Type 1 diabetes for DR4,DQw8 positive haplotypes A2,Cw4,Bw35,DR4 A3,Cw3,Bw62,DR4, A24,Cw7,Bw39,DR4, A2,Cw3,Bw62, DR4, and A2,Cw1,Bw56,DR4 was 35/100,000, 130/100,000, 166/100,000, 196/100,000, and 218/100,000, respectively. The absolute risks for DR3,DQw2 positive haplotypes A1, Cw7,B8,DR3 and A2,Cw7,B8,DR3 were 68/100,000 and 103/100,000, respectively. These results provide further evidence that not only the polymorphism at the DQ locus but also other genes of the haplotypes contribute to susceptibility to Type 1 diabetes.

Altered prolactin response of the lymphocytes of tumor-bearing mice

Interaction of prolactin and glucocorticoid on thymocytes and splenocytes of normal and tumor-bearing mice with reference to their mitogen-responsive blastogenesis has been studied. Prolactin alone had little or no mitogenic effect on thymocytes and splenocytes of normal mice but it was co-stimulatory, with ConA, in inducing blastogenesis in normal splenocytes. Thymocytes and splenocytes of tumor-bearing mice responded differently to prolactin. Hormone alone inhibited growth of thymocytes but at certain concentrations stimulated splenocytes. When cultured with prolactin and ConA, the thymocytes of tumor hosts responded with increased proliferation compared to that induced by ConA alone. Glucocorticoid suppressed ConA-induced lymphocyte proliferation in both normal and tumor-bearing mice. Prolactin reversed the inhibitory effect of glucocorticoid in normal mice but failed to abrogate inhibition in tumor hosts. Altered responsiveness of lymphocytes of tumor hosts to prolactin was not a function of circulating prolactin, as the serum prolactin level was similar in normal and tumor-bearing mice. Prolactin, however, could not reverse estradiol-induced suppression of lymphocyte proliferation. The lactogenic hormone, but not somatogenic hormones, altered the glucocorticoid inhibition of lymphocyte growth.

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.

Molecular genetic studies of major histocompatibility complex genes in children with juvenile dermatomyositis: increased risk associated with HLA-DQA1 *0501

Juvenile dermatomyositis (JDMS) is an inflammatory disease associated with HLA-DR3. We therefore undertook molecular genetic studies of HLA region genes to determine whether HLA-DR3 itself confers susceptibility to JDMS or whether susceptibility is conferred by alleles in linkage disequilibrium with HLA-DR3. Our results indicate that JDMS is associated with the HLA-DQA1 allele DQA1 *0501 on non-DR3 haplotypes in Caucasian JDMS. Furthermore, the reported of association between the C4A gene deletion and JDMS is likely due to linkage disequilibrium with HLA-DR3.

HLA antigen frequencies and Wegener's granulomatosis

Previous reports of an association between HLA tissue type and Wegener's granulomatosis are contradictory. By using for the first time a highly sensitive restriction fragment-length polymorphism (RFLP) analysis in addition to standard microcytotoxicity assays, the largest series yet investigated (41 patients) was tissue typed. No association was found between any specific HLA antigen and Wegener's granulomatosis. Although the condition appears to be immunologically mediated, this study indicates that the HLA antigens do not have a major role.

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.