The A3 allele of the HLA-DQA1 locus is associated with susceptibility to type 1 diabetes in Japanese

Hygiene hypothesis and autoimmune diseases: A narrative review of clinical evidences and mechanisms

Since the start of the "modern era", characterized by the increase in urbanization, a progressive attention to hygiene and autoimmune conditions has considerably grown. Although these diseases are often multifactorial, it was demonstrated that environment factors such as pollution, diet and lifestyles may play a crucial role together with genetic signature. Our research, based on the newest and most significant literature of this topic, highlights that the progressive depletion of microbes and parasites due to increased socioeconomic improvement, may lead to a derangement of immunoregulatory mechanisms. Moreover, special attention was given to the complex interplay between microbial agents, as gut microbiome, diet and vitamin D supplementation with the aim of identifying promising future therapeutic options. In conclusion, autoimmunity cannot be limited to hygiene-hypothesis, but from the point of view of precision medicine, this theory represents a fundamental element together with the study of genomics, the microbiome and proteomics, in order to understand the complex functioning of the immune system.

Association between copy number variations of HLA-DQA1 and ankylosing spondylitis in the Chinese Han population

Ankylosing spondylitis (AS) is a chronic inflammatory disease with complex genetic traits. Multiple sequence variations have been associated with AS, but explained only a proportion of heritability. The studies herein aimed to explore potential associations between genomic copy number variation (CNV) and AS of Han Chinese. Five AS patients were examined with the high-density comparative genomic hybridization (CGH) microarrays in the first screen test for AS associated CNVs. A total of 533 AS patients and 792 unrelated controls were examined in confirmation studies with the AccuCopy assays. A significant association was observed between the CNV of the HLA-DQA1 and AS. Comparing with controls, AS patients showed an aberrant copy number (CN), and significantly increased number of patients had more than 2 copies of the HLA-DQA1. Therefore, CNV of the HLA-DQA1 may play an important role in susceptibility to AS in Han Chinese population.

The hygiene hypothesis: an explanation for the increased frequency of insulin-dependent diabetes

The steadily increasing frequency of insulin-dependent diabetes in several countries is best explained today by the decline of infections. Epidemiologic and animal data support this conclusion, which, however, requires confirmation by intervention trials in man. The mechanisms of the protective effect of infections on diabetes onset are diverse including competition for homeostatic factors and stimulation of regulatory T cells and of Toll-like receptors. These considerations might have interesting therapeutic applications for the prevention of the disease.

Association between vitamin D receptor gene polymorphisms and type 1 diabetes mellitus in Iranian population

Type 1 diabetes mellitus (T1DM) is one of the T-cell mediated autoimmune diseases and vitamin D suppresses activation of T-cell and has immunomodulatory effects. In this study the association between four vitamin D receptor (VDR) gene polymorphisms, at positions FokI, BsmI, ApaI and TaqI, and susceptibility to T1DM was investigated. We assessed 87 Iranian patients with T1DM and one hundred healthy controls with no history of diabetes or other autoimmune diseases. Our results demonstrated that genotypes frequency of the TaqI VDR polymorphism differed significantly between T1DM patients and controls, TT genotype and T allele was more frequent in healthy controls compared with TIDM patients (P = 0.003; OR = 0.51, 95% CI = 0.31-0.84). Therefore, allele t is the risk-allele for developing TIDM in this study. No significant association was observed between others VDR SNPs and disease susceptibility. In conclusion, our case-control study indicated that the VDR TaqI polymorphism is associated with TIDM in Iranian population.

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.

Relative predispositional effects of HLA class II DRB1-DQB1 haplotypes and genotypes on type 1 diabetes: a meta-analysis

The direct involvement of the human leukocyte antigen class II DR-DQ genes in type 1 diabetes (T1D) is well established, and these genes display a complex hierarchy of risk effects at the genotype and haplotype levels. We investigated, using data from 38 studies, whether the DR-DQ haplotypes and genotypes show the same relative predispositional effects across populations and ethnic groups. Significant differences in risk within a population were considered, as well as comparisons across populations using the patient/control (P/C) ratio. Within a population, the ratio of the P/C ratios for two different genotypes or haplotypes is a function only of the absolute penetrance values, allowing ranking of risk effects. Categories of consistent predisposing, intermediate ('neutral'), and protective haplotypes were identified and found to correlate with disease prevalence and the marked ethnic differences in DRB1-DQB1 frequencies. Specific effects were identified, for example for predisposing haplotypes, there was a statistically significant and consistent hierarchy for DR4 DQB1*0302s: DRB1*0405 =*0401 =*0402 > *0404 > *0403, with DRB1*0301 DQB1*0200 (DR3) being significantly less predisposing than DRB1*0402 and more than DRB1*0404. The predisposing DRB1*0401 DQB1*0302 haplotype was relatively increased compared with the protective haplotype DRB1*0401 DQB1*0301 in heterozygotes with DR3 compared with heterozygotes with DRB1*0101 DQB1*0501 (DR1). Our results show that meta-analyses and use of the P/C ratio and rankings thereof can be valuable in determining T1D risk factors at the haplotype and amino acid residue levels.

The clinical and immunogenetic characteristics of adult-onset type 1 diabetes mellitus in Korea

Although the HLA class II alleles and immunological abnormalities are associated with type 1 diabetes mellitus (T1DM) in all racial groups, there are considerable variations in the genotypes and the prevalence of autoantibodies. In order to investigate the characteristics of the immunogenetic patterns and to use these as an early diagnostic tool and guideline for a therapeutic plan, we examined the clinical characteristics and the patterns of anti-GAD antibody (GADA), IA-2 antibody (IA-2A), HLA-DR and HLA-DQ in Korean adult-onset T1DM patients. Adult-onset patients had higher serum C-peptide levels than child-onset patients. In adult-onset patients, the prevalence of GADA and IA-2A were 59.5% and 15.3% respectively, and increased frequencies of HLADR4 and-DR9 were found. The frequencies of HLADQA1,-DQB1 and-DQ heterodimers were similar to those of the control, but child-onset patients had high frequencies of the HLA-DR3,-DR4,-DR9, DQA1*0301, DQA1*0501 and DQB1*0201 genotypes. In conclusion, Korean adult-onset T1DM patients had a lower prevalence of GADA, which was comparable to that found in Caucasian patients. The detection of GADA might help to predict the insulin dependency of adult-onset diabetes. Difference in the frequencies of diabetes associated with HLA type suggests that there might be a heterogeneity in the pathogenesis of diabetes according to the age of onset.

Polymorphisms of HLA class II predispose children and adolescents with type 1 diabetes mellitus to autoimmune thyroid disease

To determine the prevalence of autoimmune thyroid disease (AITD) in children and adolescents with type 1 diabetes mellitus (DM), and assess whether the development of AITD is correlated with specific DQ-A and DQ-B loci of the HLA class II antigens, we analyzed thyroid function using anti-thyroid antibodies and HLA-DQ-A and -DQ-B polymorphisms in 69 patients with type 1 DM, in 75 normal healthy controls, and in 21 patients with AITD but without type 1 DM. Eighteen patients (26%) in the diabetic patients had AITD. In the diabetic patients, DQA1*0301 and DQB1*0302 occurred more frequently than in controls [DQA1*0301: OR = 1.939, 95% CI = 1.210-3.109 (P = 0.008, P(c) (corrected P) < 0.05); DQB1*0302: OR = 2.558, 95% CI = 1.354-4.832 (P = 0.005, P(c), > 0.05)]. Compared with controls, non-diabetic subjects with AITD showed higher frequency of DQA1*0301 (P(c), < 0.05) and DQB1*0601 (P(c) > 0.05), but these alleles were not contributing factors in the development of AITD in diabetic patients. In diabetic patients, DQB1*0201, known as susceptible allele of type 1 DM was not a contributing factor in the development of AITD in diabetic patients. Unlike DQB1*0201, DQB1*0401 was more frequently found in diabetic patients with AITD than in controls [OR = 4.053, 95% CI = 1.607-10.221 (P = 0.0017, P(c) < 0.05)] or than in non-diabetic AITD patients [OR = 15.769, 95% CI = 1.905-130.530(P = 0.002, P(c) < 0.05)]. In non-diabetic subjects, DQB1*0401 did not provide susceptibility for AITD. Our results suggest that HLA DQB1*0401 is a predisposing genetic marker for the development of AITD in patients with type 1 DM in Korea.

TNFA-TNFB haplotypes modify susceptibility to type I diabetes mellitus independently of HLA class II in a Moroccan population

The contribution of single nucleotide polymorphisms in tumor necrosis factors (TNF) alpha and beta to autoimmune diseases, and to type 1 diabetes mellitus (T1DM) in particular, is not well established, and may be confounded by linkage disequilibrium to class II HLA genes. At least two polymorphisms seem to have functional relevance in the respective genes: TNFA-307 and TNFB+252. We have typed these two polymporphisms in samples of Moroccan T1DM patients and controls for which class II HLA genes had already been typed. Tumor necrosis factors and compound TNF-class II HLA haplotypes were inferred; it was the first time that such a design had been implemented. Independent of linkage disequilibrium with class II HLA, TNF haplotype TNFA-307*2 - TNFB+252*2 showed a significant protective effect (OR = 0.031), partly exacerbated by partial linkage to protective class II haplotypes. Such effect could be detected because Morocco shows the highest frequency of the TNFA-307*2 allele yet reported. This highlights the possible population differences in alleles contributing to autoimmune diseases.

Type 1A diabetes mellitus-associated autoimmunity

Type 1A diabetes mellitus has become one of the most intensively studied autoimmune disorders, with characterized animal models and extensive prospective studies of the development of anti-islet autoimmunity. It is now possible to predict the development of type 1A diabetes mellitus, beginning with HLA-encoded genetic susceptibility, followed by the development of a series of anti-islet autoantibodies. Prediction primarily is based on the detection of multiple anti-islet autoantibodies reacting with cloned islet antigens. Multiple international workshops fostered the development of specific and sensitive radioassays for autoantibodies reacting with GAD65 (glutamic acid decarboxylase), ICA512 (also termed IA-2, a tyrosine phosphatase-like protein), and insulin. Similar high throughput radioassays have been applied using autoantigens for additional autoimmune disorders including celiac disease and Addison's disease. Relatives of patients with type 1A diabetes mellitus inherit susceptibility to express multiple autoantibodies, and a subset of autoantibody-positive individuals inherit susceptibility to progress to overt disease. This article reviews autoimmune disorders associated with type 1A diabetes mellitus.

The combination of several polymorphic amino acid residues in the DQalpha and DQbeta chains forms a domain structure pattern and is associated with insulin-dependent diabetes mellitus

IDDM is positively associated with HLA-DQA1*0301-DQB1*0302 (DQ8) and DQA1*0501-DQB1*0201 (DQ2) and negatively associated with DQA1*0102-DQB1*0602 (DQ6). The aim of the present study was to analyze the importance of several polymorphic residues and domains of DQalpha and DQbeta, in addition to residue 52 DQalpha and residue 57 DQbeta, with regard to susceptibility or resistance in new-onset 0- to 15-year-old Swedish children with IDDM (n = 425) and matched controls (n = 367). HLA genotyping identified several polymorphic residues of the DQalpha and DQbeta to be either positively or negatively associated with IDDM, including Arg 52 DQalpha and Asp 57 DQbeta. Leu 69 DQalpha was positively (OR 7.02, P < 0.0001), Ala 69 DQalpha was negatively (OR 0.22, P < 0.0001), Gln 47 DQalpha was positively (OR 5.8, P < 0.0001), Cys 47 DQalpha was positively (OR 2.2, P < 0.0001), Lys 47 DQalpha was negatively (OR 0.47, P < 0.005), and Arg 47 DQalpha was negatively (OR 0.22, P < 0.005) associated with IDDM. Similarly, residues at 11, 18, 45, 48, 50, 53, 55, 61, 64, 66, 76, and 80 were either positively or negatively associated with IDDM. Likewise, for DQbeta, Leu 53 DQbeta was positively (OR 11.01, P < 0.0001), Gln 53 DQbeta was negatively (OR 0.22, P < 0.0005), Arg 70 DQbeta was positively (OR 11.01, P < 0.0001), and Gly 70 DQbeta was negatively (OR 0.19, P < 0.0001) associated like other residues at 71, 74, 84, 85, 86, 89, and 90 DQbeta with IDDM. Certain domains in the DQalpha, RFTIL (at DQalpha positions 52, 61, 64, 66, and 69), were present in 95% of patients compared to 69% of controls (OR 9.01, P(c) < 0.0001), and DQbeta domain GR (at DQbeta positions 45 and 70) was present in 95% of patients and 68% of controls (OR 8.68, P < 0.0001), which correlated better than the individual amino acid residues with IDDM. A combination of the DQalpha and DQbeta chain domains was present in 94% of patients compared to 60% of controls (OR 10.6, P < 0.001). In conclusion, domains in the DQalpha, DQbeta, or both in the DQ molecule explain susceptibility or resistance to IDDM better than individual amino acid residues of DQA1 and DQB1.

Human leukocyte antigen-A24 and -DQA1*0301 in Japanese insulin-dependent diabetes mellitus: independent contributions to susceptibility to the disease and additive contributions to acceleration of beta-cell destruction

The aim of this study is to identify insulin-dependent diabetes mellitus (IDDM)-susceptible HLA antigens in IDDM patients who do not have established risk allele, HLA-DQA1*0301, and analyze relationship of these HLA antigens and the degree of beta-cell destruction. In 139 Japanese IDDM patients and 158 normal controls, HLA-A, -C, -B, -DR and -DQ antigens were typed. Serum C-peptide immunoreactivity response (deltaCPR) to a 100-g oral glucose load < or = 0.033 nmol/l was regarded as complete beta-cell destruction. All 14 patients without HLA-DQA1*0301 had HLA-A24, whereas only 35 of 58 (60.3%) normal controls without HLA-DQA1*0301 and only 72 of 125 (57.6%) IDDM patients with HLA-DQA1*0301 had this antigen (Pc = 0.0256 and Pc = 0.0080, respectively). DeltaCPR in IDDM patients with both HLA-DQA1*0301 and HLA-A24 (0.097 +/- 0.163 nmol/L, mean +/- SD, n = 65) were lower than in IDDM patients with HLA-DQA1*0301 only (0.219 +/- 0.237 nmol/L, n = 45, P < 0.0001) and in IDDM patients with HLA-A24 only (0.187 +/- 0.198 nmol/L, n = 14, P = 0.0395). These results indicate that both HLA-DQA1*0301 and HLA-A24 contribute susceptibility to IDDM independently and accelerate beta-cell destruction in an additive manner.

Combinations of HLA DR and DQ molecules determine the susceptibility to insulin-dependent diabetes mellitus in Koreans

The association of HLA-DRB1 and DQB1 genes with IDDM in Koreans was assessed using 115 IDDM patients and 140 nondiabetic controls. DQB1*0201 is the only DQB1 allele positively associated with IDDM while DQB*0602, *0601 and *0301 are negatively associated. Three DRB1 alleles (DRB1*0301, DRB1*0407 and DRB1*0901) are positively associated while four DR allele groups (DRB1*15, DRB1*12, DRB1*10 and DRB1*14) are negatively associated. However, Haplotype analyses indicated that DQB1*0302, DRB1*0405 and DRB1*0401 may confer susceptibility because the DRB1*0405-DQB*0302 and DRB1*0401-DQB1*0302 haplotypes are positively associated with the disease. The lack of association in Koreans with the DQB1*0302 allele, which appears predisposing in studies of non-Orientals, is due to its strong linkage disequilibrium (LD) with the protective DRB1*0403 and *0406 alleles, while the lack of association with DRB1*0405 is because of its strong LD with the protective DQB1*0401 allele. Nine DR/DQ genotypes confer significantly increased risk to IDDM. Seven of the nine genotypes (DR3/4s, DR1/4s, DR4s/13, DR4s/8, DR4s/7, DR9/13 and DR3/9) were also found to be at high risk to IDDM in other populations, while the two others (DR1/9 and DR9/9) are only found in Koreans. Surprisingly, DR4/4 homozygotes are not associated with high risk to IDDM in Koreans. This observation can be explained by the high frequency of protective DR4 subtypes and the protective DQ alleles (0301 and 0401) associated with the susceptible DR4 alleles. Our analyses indicate that the counterbalancing act between susceptible DRB1 and protective DQB1, and vice versa, that has already been observed in Chinese and Japanese, is the major factor responsible for the low incidence of diabetes in Koreans.

A comparison of three statistical models for IDDM associations with HLA

The association between HLA-DQ haplotypes and insulin-dependent diabetes mellitus (IDDM) was studied in 48 children from 44 families ascertained from the high incidence area around Umeå, Sweden. Numerous hypotheses have been proposed to explain associations between HLA and IDDM, but comparisons of statistical models based on these hypotheses have not been attempted. The aim of the present study was to compare the goodness-of-fit and predictive abilities among different statistical models. A likelihood-based analysis rather than a conventional analysis based on contingency tables was therefore adopted. We first used parental haplotype information in a conditional likelihood analysis (1) and then compared this analysis with that of an unaffected control group which used information on geographically matched controls. Under the analysis conditional on parental haplotype, a statistical model motivated by the hypothesis that the entire DQ heterodimer is involved in IDDM pathogenesis fit the data significantly better and had greater predictive ability than either a model motivated by the explanation that an IDDM gene is linked to DQB1 or that the DQB1 chain itself is involved in IDDM pathogenesis, or a model arising from the hypothesis that single amino acids at codon 57 of DQB1 and codon 52 of DQA1, respectively, confer susceptibility. Under the case-control analysis, the identity of the best-fitting or more predictive statistical model was not as clear, although both approaches to analyzing risk suggested that the single-amino-acids model had significantly poorer fit compared to the remaining two models.

Analysis on allelic variation of the HLA-DMB gene in Japanese by PCR-RFLP as well as direct DNA sequencing and identification of a new DMB allele, DMB*0105

In the HLA-D region, one of the class II genes, DMA and DMB have been identified between the DQ and DP genes, and four allelic polymorphisms in each of the DMA (DMA*0101 approximately 0104) and DMB (DMB*0101 approximately 0104) genes have been so far recognized. Several recent studies suggested that the DM molecule is required for class II antigen presentation pathway especially by promoting the binding of antigenic peptides to the classical HLA class II molecule. In this study, we have analyzed genetic polymorphism and allelic variation of the DMB gene in a Japanese population by the direct DNA sequencing technique and also by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method, and could recognize DMB*0101 (49.3%), DMB*0102 (23.2%), DMB*0103 (23.2%), and DMB*0104 (0.4%). Further, a new DMB allele, DMB*0105 characterized by the presence of Val and Ile at two polymorphic sites, codons 144 and 179, respectively was identified. Strong linkage disequilibria were found between DMB*0101 and DRB1*0101, DPB1*0402 and DRB1*1502, and also between DMB*0103 and DRB1*1501 and DQB1*0602. HLA-DMB genotyping using the PCR-RFLP method established here will provide accurate evaluation of the effects of sequence allelism in the DMB gene on the HLA class II disease associations.

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.

Population analysis of protection by HLA-DR and DQ genes from insulin-dependent diabetes mellitus in Swedish children with insulin-dependent diabetes and controls

A negative association between insulin-dependent diabetes mellitus (IDDM) and HLA-DR, DQA1 or DQB1 was found in a large population-based investigation of childhood-onset patients (more than 420 patients) and controls (more than 340 controls) from Sweden. The relative risk was decreased for several haplotypes that were negatively associated with IDDM: DR15-DQA1*0102-DQB1*0602, DR7-DQA1*0201-DQB1*0303, DR14-DQA1*0101-DQB1*0503, DR11-DQA1*0501-DQB1*0301, DR13-DQA1*0103-DQB1*0603 and DR4-DQA1*0301-DQB1*0301. In a relative predispositional effect (RPE) analysis, however, only the DR15-DQA1*0102-DQB1*0602 haplotype was significantly decreased, which suggests that the major protective effect for IDDM is carried by this haplotype. This was supported by the observation that all genotypes which were negatively associated with IDDM, except DR7/13, included at least one allele from the DR15-DQA1*0102-DQB1*0602 haplotype. Relative predispositional effect (RPE) analysis of genotypes showed further that the DR15-DQA1*0102-DQB1*0602 haplotype was also negatively associated with IDDM when combined with any other haplotype, whether negatively or positively associated with IDDM. This supports previous suggestions that DR15-DQA1*0102-DQB1*0602 acts dominantly. However, both the stratification and the predispositional allele test failed to distinguish the negative association between IDDM and DR15 from that of DQB1*0602. On the other hand, these tests indicated that DQA1*0102 was not likely to explain the negative association between IDDM and the DR15-DQA1*0102-DQB1*0602 haplotype. We conclude that the major protective effect for IDDM in the population of Swedish children is conferred by the DR15-DQA1*0102-DQB1*0602 haplotype in a dominant fashion, the DQB1*0602 allele being the allele most likely to be responsible for the protective effect of this haplotype, although an effect of the DR15 allele could not be excluded.

IDDM susceptibility associated with polymorphisms in the insulin gene region. A study of blacks, Caucasians and orientals

Previous studies have suggested an association between polymorphisms in the insulin gene region and insulin-dependent diabetes mellitus (IDDM). Most of the studies so far have been performed in Caucasoid populations. We have investigated 418 random IDDM patients and 422 healthy control subjects from three different ethnic groups; Tanzanian blacks, Norwegian Caucasians and Japanese orientals. Our data suggest that polymorphisms in the insulin gene region confer susceptibility to IDDM in Caucasians, and that a similar tendency though not statistically significant is observed among Tanzanian blacks, while no significant contribution is seen among Japanese orientals. We further demonstrate that the disease-associated genotype INS +/+ confers susceptibility independently of HLA class II alleles associated with IDDM. Compared to the contribution of particular HLA-DQ alleles in IDDM susceptibility, the additional risk conferred by the insulin gene region polymorphism is, however, small. Genotyping of the insulin gene region will therefore most probably not be a useful tool in the prediction of IDDM.

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.

HLA-D and T lymphocyte reactivity to specific periodontal pathogens in type 1 diabetic periodontitis

Bacterial antigen fragments complexed with class II major histocompatibility molecules (HLA-D) on antigen presenting cells (APCs) stimulate CD4+ T lymphocyte proliferation, presumably to protect the host. This study examined these responses to antigens of two periodontal pathogens in four groups (n = 15) of age- (young adult) and sex-matched Caucasian subjects with or without type 1 diabetes and moderate to severe periodontitis: Group DP = diabetics with periodontitis; Group DnP = diabetics without periodontitis; Group nDP = nondiabetics with periodontitis; and Group nDnP = nondiabetics without periodontitis. HLA-D phenotypes for each subject were determined by lymphocytotoxicity assays. T lymphocytes purified from peripheral blood were stimulated in cell culture with APC pulsed with various concentrations of tetanus toxoid, Porphyromonas gingivalis, and Capnocytophaga sputigena antigens. T lymphocyte reactivity (3H thymidine incorporation) was numerically lower in cultures from diabetics stimulated with unpulsed APC (not significant), and antigen-pulsed cultures showed low proliferation and no significant differences among groups. Stimulation indices in cultures from diabetic patients stimulated with P. gingivalis or C. sputigena, however, were significantly elevated at all antigen concentrations compared to nondiabetic cultures. The occurrence of HLA-DR4 was moderately associated with diabetes (P < 0.05) and highly associated with periodontitis (P < 0.001, log-linear model for categorical variables); and HLA-DR53 and HLA-DQ3 were significantly associated with periodontitis (P < or = 0.02). HLA-DR was crucial to lymphocyte stimulation (anti-HLA-DR blocking experiments), but the low peripheral blood T cell reactivity to antigens of periodontal pathogens could not be linked with HLA-D type or periodontitis susceptibility.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of HLA-DQA1 and -DQB1 genes in Mexican Americans with insulin-dependent diabetes mellitus

Mexican American patients (n = 35) with insulin-dependent diabetes mellitus (IDDM) and control subjects (n = 39) were HLA-DQA and DQB typed by the polymerase chain reaction technique combined with allele-specific oligonucleotide probes. Either DQB1*0302 or DQB1*0201 was present among 91% (32/35) of the patients compared to 67% (26/39) of controls. Either DQA1*0501 or DQA1*0301 was present in all patients (100% or 35/35) compared to 29/39 (74%) (OR 12.06 Pc < 0.05) of controls. All four of these genes, in cis or trans, were present in 15/35 (43%) of the patients compared to 3/39 (8%) of controls (OR 9.0; Pc < 0.01). The presence of one or more non-susceptibility alleles showed a dose-related decrease in relative risk. Presence of aspartic acid (Asp) at position 57 of the DQ beta chain did not confer protection and non-Asp homozygosity did not confer susceptibility to IDDM in this ethnic group. In conclusion, susceptibility to IDDM in Mexican Americans is associated with particular DQA and DQB combinations, illustrates dose-dependent parameters and contradicts the critical residue hypothesis.

HLA-DQ primarily confers protection and HLA-DR susceptibility in type I (insulin-dependent) diabetes studied in population-based affected families and controls

The association between HLA-DR and -DQ and insulin-dependent diabetes mellitus (IDDM) in a defined high-incidence area was analyzed in a total of 58 population-based patients, representing 77% of IDDM patients with age at onset below 16 years, and in 92 unrelated parents in control families without IDDM. HLA haplotypes were confirmed by analyzing first-degree relatives in both groups. Seven different methods were used to analyze risk: (1) odds ratio, (2) absolute risk, (3) haplotype relative risk, (4) transcomplementation relative risk, (5) relative predisposing effects, (6) stratification analysis, and (7) test of predisposing allele on haplotype. DQB1*0302 indicated somewhat higher risk than did DR4, while DR3 had a higher risk than DQB1*0201; however, the 95% confidence intervals of the risk estimates overlapped. The positive association between IDDM and the DQB1*0201-DQA1*0501-DR3 haplotype seems to be due to DR3 or to an unknown linked gene. More important, DQA1*0301 was present among 93% of the patients, and this allele in various transcomplementation combinations with DQB1 alleles showed closer association to IDDM than did any other alleles. The strong negative association of the DQB1*0602 allele also in the presence of either DR4 or DQB1*0302 or both suggests that, in a high-risk population for IDDM, HLA-DQ primarily confers protection, perhaps by induction of tolerance. Consistent with known functions, HLA-DR may primarily confer susceptibility, perhaps by induction of autoreactive T lymphocytes.

Both DQA1 and DQB1 genes are implicated in HLA-associated protection from type 1 (insulin-dependent) diabetes mellitus in a British Caucasian population

Inherited susceptibility to Type 1 (insulin-dependent) diabetes mellitus is partly determined by HLA genes. It has been suggested that protection from disease may be conferred by HLA-DQB1 genes which encode molecules with aspartate at position 57. We investigated the contributions of HLA-DRB1, DQA1 and DQB1 genes to protection from disease. Restriction fragment length polymorphism and sequence specific oligonucleotide analysis in 156 British Caucasian Type 1 diabetic and 116 control subjects showed protection from disease was associated with DR2, DRw6 and DR7 haplotypes. The most protective DQA1 allele was DQA1*0102 which occurred on both DR2 and DRw6 haplotypes. The DQB1 alleles DQB1*0303, DQB1*0602 and DQB1*0603 were associated with protection, as was DQB1*0604, which encodes an Asp-57 negative DQ beta molecule. Heterozygosity for both protective and predisposing HLA markers was reduced in diabetic compared with control subjects. We conclude that both DQA1 and DQB1 genes are implicated in HLA-associated protection from Type 1 diabetes in this British Caucasian population. The overall structure of the DQ heterodimer is critical and DQ beta-Asp 57 is of secondary importance in determining protection from disease. The effect of protective HLA types may predominate over that of predisposing markers.

Genes for insulin-dependent diabetes mellitus (IDDM) in the major histocompatibility complex (MHC) of African-Americans

Mapping the MHC-associated susceptibility and resistance factors for insulin-dependent diabetes mellitus (IDDM) has been difficult due to the strong linkage disequilibrium within the HLA-DR-DQ region. Previous analyses have suggested that the study of IDDM-associated haplotypes in different races might be useful for identifying the responsible genes. We have performed complete HLA class II genotyping to study susceptibility and resistance to IDDM in 34 randomly selected African-American IDDM patients and 69 ethnically-matched controls. IDDM patients showed highly significant increases of DRB1*0301, DRB1*0401, DRB1*0405, DQA1*0301, DQA1*0302, DQB1*0201 and DQB1*0302. Analysis of DQA1-DQB1 associations showed that DQA1*03 combined with both DQB1*0201 and DQB1*0302 gave the highest odds ratio, suggesting a synergistic effect due to formation of heterodimers encoded both in cis and in trans. Among the subsets of DR4, only DRB1*0401 and DRB1*0405 were increased in diabetic patients. Interestingly, DQB1*0602 and DQB1*0301, which have previously been thought to encode resistance factors in Caucasians, were not significantly decreased and, after removal of known susceptibility haplotypes, were found to have essentially identical frequencies in patients and controls.

Homozygous parent affected sib pair method for detecting disease predisposing variants: application to insulin dependent diabetes mellitus

For complex genetic diseases involving incomplete penetrance, genetic heterogeneity, and multiple disease genes, it is often difficult to determine the molecular variant(s) responsible for the disease pathogenesis. Linkage and association studies may help identify genetic regions and molecular variants suspected of being directly responsible for disease predisposition or protection, but, especially for complex diseases, they are less useful for determining when a predisposing molecular variant has been identified. In this paper, we expand upon the simple concept that if a genetic factor predisposing to disease has been fully identified, then a parent homozygous for this factor should transmit either of his/her copies at random to any affected children. Closely linked markers are used to determine identity by descent values in affected sib pairs from a parent homozygous for a putative disease predisposing factor. The expected deviation of haplotype sharing from 50%, when not all haplotypes carrying this factor are in fact equally predisposing, has been algebraically determined for a single locus general disease model. Equations to determine expected sharing for multiple disease alleles or multiple disease locus models have been formulated. The recessive case is in practice limiting and therefore can be used to estimate the maximum proportion of putative susceptibility haplotypes which are in fact predisposing to disease when the mode of inheritance of a disease is unknown. This method has been applied to 27 DR3/DR3 parents and 50 DR4/DR4 parents who have at least 2 children affected with insulin dependent diabetes mellitus (IDDM). The transmission of both DR3 and DR4 haplotypes is statistically different from 50% (P < 0.05 and P < 0.001, respectively). An upper estimate for the proportion of DR3 haplotypes associated with a high IDDM susceptibility is 49%, and for DR4 haplotypes 38%. Our results show that the joint presence of non-Asp at DQ beta position 57 and Arg at DQ alpha position 52, which has been proposed as a strong IDDM predisposing factor, is insufficient to explain the HLA component of IDDM predisposition.

The HLA-DRB1*0405 haplotype is most strongly associated with IDDM in Algerians

Insulin-dependent diabetes mellitus (IDDM) in Caucasians is strongly associated with HLA-DR3-DQ2 and DR4-DQ8. In order to investigate the HLA class II associations with IDDM in Algerians, we have used polymerase chain reaction (PCR) and sequence specific oligonucleotide analysis (SSO) to identify DQA1, DQB1, and DRB1 alleles, haplotypes and genotypes in 50 unrelated IDDM patients and 46 controls from a homogeneous population in Western Algeria. Both DRB1*0301-DQA1*0501-DQB1*0201 (DR3-DQ2) and DRB1*04-DQA1*0301-DQB1*0302 (DR4-DQ8) haplotypes were found at increased frequencies among the patients compared to controls (45% vs. 13%, RR = 5.5, Pc < 10(-5) and 37% vs. 4%, RR = 12.9, Pc < 10(-4), respectively). Among the latter, in contrast to other Caucasian populations, only DRB1*0405-DQA1*0301-DQB1*0302 was significantly increased in the Algerian patients (25% vs. 1% in controls, RR = 30.3, Pc < 10(-3). Accordingly, the highest risk of disease was observed in DRB1*0301-DQA1*0501-DQB1*0201/DRB1*0405-DQA1+ ++*0301-DQB1*0302 heterozygotes (34% in patients vs. 0% in controls; RR = 49; Pc < 10(-3). This observation and its comparison with DR-DQ haplotypes in other ethnic groups suggest that the DRB1*0405 allele which encodes an Asp57-negative beta chain may contribute to IDDM susceptibility in a similar way as Asp57-negative DQ beta chains.

Identification of Genetic Susceptibility loci for Insulin-Dependent Diabetes in sudan

In this study we report, for the first time, the molecular analysis of HLA-DR and DQ gene frequencies in a large cohort of well-characterized type 1 (insulin-dependent) diabetes mellitus (IDDM) patients (n = 72), and ethnically matched controls (n = 59) collected in sub-Saharan Africa. High molecular mass DNA was prepared and analysed in Southern blots and by oligonucleotide typing. We have shown a strong positive association between IDDM and the Asp 57- DQB1 allele *0201 (DQw2). A rare DR4, DQw2 haplotype was also identified at high frequency in the IDDM cohort. We can now confirm that the association between Asp 57- DQB1 alleles and IDDM, previously reported in ethnically diverse cohorts collected in Western Europe, North America, and South Asia, is also present in an IDDM cohort collected in Africa.

Case report of an insulin-dependent diabetes multiplex family with a pair of identical twins

The following is a case of a family with a pair of identical twins and a family history of insulin-dependent diabetes mellitus (IDDM). A 2 year old identical twin was first admitted to our hospital and diagnosed as IDDM based on diabetic ketoacidosis. His father has been treated with insulin since the diagnosis of IDDM at the age of 17. All family members had the HLA-DR4 and DQA1*0301 alleles, which are strongly associated with IDDM. The DR-DQ haplotypes of the father and both twins were DR4-DQW8 (DQB1*0302), which increases susceptibility to IDDM. Islet cell antibodies were positive only in the index twin at the time of diagnosis. The co-twin was considered to have beta-cell dysfunction based on the result of an intravenous glucose tolerance test.

Nucleotide sequencing of HLA-DQ gene second exons in Chinese homozygous cells

Six HLA class I and class II-homozygous Chinese cell lines with unique HLA-Dw types were studied. Since the majority of HLA class II nucleotide sequence polymorphism is localized within the second exons of the genes, we used the polymerase chain reaction (PCR) to amplify these regions in HLA-DQA and DQB genes and subsequently determined the nucleotide sequences. No unique DQA1 or DQB1 alleles were found. However, a new haplotype of DQA1*0601-DQB1*0301-DRB1*1202 was found in two cells; and DQA1*03011 was found in association with DR9 in another two cells. This indicates that new DR-DQ associations may explain the observed new HLA-Dw types. The DQB2 sequences were identical in all six cells and were identical to a sequence previously reported in a DR6 haplotype. The DQA2 sequences from two clones obtained from two cells differed from each other and from previously reported sequences. The results show that the DQA1 and DQB1 alleles in the Chinese individuals studied are as previously reported in Caucasian populations and as such may be typed by restriction fragment-length polymorphism (RFLP) or PCR-sequence-specific oligonucleotide typing (PCR-SSO) or PCR-RFLP using conventional probe or restriction enzyme sets.

Genetic epidemiology of insulin-dependent diabetes mellitus: international comparisons using molecular genetics

International comparative molecular studies of insulin-dependent diabetes mellitus can be viewed from an immunogenetical and an epidemiological perspective. Each approach independently contributes to our knowledge concerning the etiology and prevention of the disease. However, the combination of these perspectives, representing an interface between molecular biology and epidemiology, will achieve more in terms of scientific advancement and public health than either perspective alone. An excellent example of the development of molecular epidemiology has been the evolution of international comparative research through the WHO Multinational Project for Childhood Diabetes. Case-control molecular studies are currently being conducted to test the hypothesis that population variation in the frequency of HLA class II susceptibility alleles is the primary determinant of the global patterns of insulin-dependent diabetes mellitus incidence. Preliminary data suggest that this hypothesis is correct. Future international molecular epidemiological studies, encompassing host-environment interactions, will lead to a better understanding of the relationships among specific risk factors within populations and across the world. Molecular epidemiology represents a new paradigm for studying the etiology and epidemiology of infectious and non-communicable diseases, and no doubt represents a major challenge for the 1990s.

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.

Investigation of the mode of inheritance of insulin-dependent diabetes mellitus in Japanese subjects

Previous studies have shown that insulin-dependent diabetes mellitus is positively associated with HLA-DR4 and HLA-DR9 in Japanese populations. It was proposed that susceptibility to the disease is determined by a single HLA allele associated with both DR4 and DR9. DR genotypes in a Japanese population with insulin-dependent diabetes mellitus were determined by DRB/DQB RFLP analysis. A single disease-susceptibility-allele model was tested by the antigen-genotype-frequency-among-patients method. Recessive and additive inheritance of a single susceptibility allele were rejected. The DR9-associated disease-susceptibility allele in Japanese subjects is distinct from both the DR3- and DR4-associated susceptibility alleles in white Caucasians. The data suggest further complexity in the inheritance of HLA-associated susceptibility to insulin-dependent diabetes mellitus.

Genetic analysis of HLA class II alleles and susceptibility to type 1 (insulin-dependent) diabetes mellitus in Japanese subjects

Although HLA-DQB1 alleles encoding aspartic acid at position 57 (Asp-57) are protective against Type 1 (insulin-dependent) diabetes mellitus in Caucasians, most Japanese Type 1 diabetic patients carry at least one Asp-57 DQB1 allele. We analysed the DRB1, DQA1 and DQB1 genes of 99 Japanese patients and 86 control subjects with polymerase chain reaction and sequence-specific oligonucleotide hybridization. We found that (1) the DQA1*0301 allele was significantly increased in Type 1 diabetic patients (RR7.8, pc less than 0.0001); (2) the DRB1*0405 (Dw15) allele, which is a subtype of DR4 haplotype, was significantly increased in DR4-positive patients (RR 12.0, pc less than 0.001); and (3) although the DRw8-DQw8 haplotype was positively associated with Type 1 diabetes, the DRB1*0406-DQw8 haplotype was decreased in the diabetic patients. These data indicate that DRB1 and DQA1 genes also confer susceptibility to Type 1 diabetes in Japanese.

Different genetic backgrounds for malnutrition-related diabetes and type 1 (insulin-dependent) diabetes mellitus in south Indians

HLA-DRB, -DQA and -DQB genes were studied in ten South Indian malnutrition-related diabetic patients, ten Type 1 (insulin-dependent) diabetic patients and 45 control subjects, by TaqI restriction fragment length polymorphism analysis. The DR7,DQw9 haplotype was found to be frequent in patients with malnutrition-related diabetes (p less than 0.01). The DRw17,DQw2 haplotype was overrepresented in the patients with Type 1 diabetes compared to control subjects (p less than 0.05). In vitro amplification of the polymorphic second exon of DQB genes by the polymerase chain reaction technique was performed on DNA from 10 malnutrition-related diabetic patients, 10 Type 1 diabetic patients and 13 control subjects, as they belong to a new population. Hybridization with sequence-specific oligonucleotide probes for DQB1 alleles showed homozygosity of aspartic acid at position 57 in 7 of 10 malnutrition-related diabetic patients compared to 2 of 10 Type 1 diabetic (p less than 0.05) and 15 of 45 control subjects (p less than 0.05). Homozygosity of non-aspartic acid at position 57 was present in 7 of 10 Type 1 diabetic compared to 0 of 10 malnutrition-related diabetic patients (p less than 0.005) and 3 of 45 control subjects (p less than 0.05). This study has confirmed the association of DQB1 57 non-asp in South Indians with Type 1 diabetes. In addition, our data clearly show that the genetic background of malnutrition-related diabetes mellitus is different from that of Type 1 diabetes.

Analysis of HLA-DQA1 in Japanese patients with type 1 diabetes mellitus, using DNA-PCR-RFLP typing

DNA-polymerase chain reaction(PCR)-RFLP(restriction fragment length polymorphism) typing of the DQA1 gene was performed on 39 patients with type 1 diabetes and 30 controls. Analysis of the frequency of the subtypes of DQA1 alleles, using the DNA-PCR-RFLP typing technique, showed that the DQA1*0301 subtype was most strongly associated with the disease (97.4% vs 56.7%, R.R. = 19.8, pc less than 0.00005). These results indicated that DQA1*0301 may determine the disease susceptibility in the Japanese. In addition, we analyzed the frequency of the subtypes of DQA1 genes in the ten patients carrying the DRW8-DQW8 haplotype, and found that at least eight of them (80%) were classified as having DQA1*0301. The DRW8-DQW8-DQA1*0301 may be one of the susceptible haplotypes among the Japanese.

A model for the role of HLA-DQ molecules in the pathogenesis of juvenile chronic arthritis

Restriction fragment length polymorphism (RFLP) typing of MHC-class II loci DRB, DQA1, DQB1, DQA2 and DPB1 was performed in 94 patients with seronegative juvenile chronic arthritis (JCA) and 184 random controls. Analysis of allele frequencies and MHC-class II 4-loci haplotypes indicate: (1) Susceptibility to JCA is more strongly associated with the HLA-DQ subregion than with the HLA-DR subregion, especially in early onset pauciarticular JCA (EOPA-JCA). (2) Haplotype and sequence analysis show two independent MHC-class II associations for susceptibility to EOPA-JCA, one located in DQA1, the other in DPB1. (3) Two RFLP defined patterns of the DQA1 locus, DQA1.5 (DQA1*0501) and DQA1.8 (DQA1*0401, *0601) are strongly associated with the disease. (4) Analysis of amino-acid (AA) sequences coded in exon 2 of DQA1 reveals an AA sequence of six AAs common to all three associated DQA1 alleles. This suggests a model that includes a functional role for HLA-DQ molecules in the pathogenesis of JCA.

Analysis of HLA-DR and -DQ gene polymorphisms in Sudanese patients with type 1 (insulin-dependent) diabetes

In this study we report for the first time, the molecular analysis of HLA-DR and -DQ gene frequencies in a large cohort of well characterized type 1 (insulin-dependent) diabetes mellitus (IDDM) patients (n = 72), and ethnically matched controls (n = 59) collected in sub-Saharan Africa. High molecular mass DNA was prepared and analyzed in Southern blots with DRB1, DQA1, and DQB1 probes. By identifying DR and DQ allele-specific restriction fragment length polymorphisms (RFLPs), we have shown a strong positive association between IDDM and the Asp 57- DQB1 allele *0201 (DQw2). A rare DR4, DQw2 haplotype was also identified at high frequency in the IDDM cohort. We can now confirm that the association between Asp 57-DQB1 alleles and IDDM, previously reported in ethnically diverse cohorts collected in Western Europe, North America, and South Asia, is also present in an IDDM cohort collected in Africa.

Distribution of HLA-DRB1, -DQA1 and -DQB1 alleles and DQA1-DQB1 genotypes among Norwegian patients with insulin-dependent diabetes mellitus

We have studied 87 unrelated Caucasian insulin-dependent diabetes mellitus (IDDM) patients and 181 healthy controls by oligotyping for 20 DRB1, eight DQA1 and 13 DQB1 alleles, and established their DR-DQ haplotypes and DQ genotypes. An increase of DRB1 alleles encoding DR4 was found among IDDM patients, but the distribution of DR4 subtypes did not differ among DR4-positive IDDM patients and controls. The frequency of certain DRB1-DQA1-DQB1 haplotypes and DQA1-DQB1 genotypes was significantly increased among IDDM patients. Taken together, the data suggest that IDDM is primarily associated with several (at least five) different DQ alpha beta heterodimers.

HLA-DQA1*1 contributes to resistance and A1*3 confers susceptibility to type 1 (insulin-dependent) diabetes mellitus in Japanese subjects

In this study HLA-DQA1 and TNF genes in addition to HLA-DQB1 gene were investigated at DNA level for elucidation of the genetic backgrounds of Type 1 (insulin-dependent) diabetes mellitus in Japanese subjects. DNA, amplified by polymerase chain reaction, was subjected to allele specific oligonucleotide dot blot analysis, restriction fragment length polymorphism analysis or DNA sequencing. Polymorphism of the TNF gene to NcoI did not correlate with Type 1 diabetes in Japanese patients. DQw1.2 had a protective effect against the disease, the DQA1*1 allele was significantly decreased and DQA1*3 allele was significantly increased. Seventeen out of twenty-two Type 1 diabetic patients (77%) were homozygous for DQA1*3 and five out of twenty-two (23%) heterozygous. The DQA1*3 gene of Type 1 diabetic patients had a normal nucleotide sequence. Furthermore, DQA1*3 was found unexpectedly in two patients without DR4 or DR9. These data indicate that DQA1 gene confers susceptibility and resistance to Type 1 diabetes in Japanese subjects.

HLA-DRB and DQB typing by a combination of serology, restriction fragment length polymorphism analysis and oligonucleotide probing

DNA sequencing has revealed extensive polymorphism within the HLA-DRB and DQB genes of the major histocompatibility complex. At least 43 alleles of the DRB loci and 13 alleles of the DQB1 locus are currently recognized. Identification of these alleles can be performed phenotypically by cellular and serological techniques or genotypically by restriction fragment length polymorphism (RFLP) analysis and sequence-specific oligonucleotide (SSO) probing of DNA amplified by the polymerase chain reaction (PCR). However, each method has its technical limitations so the tissue typing laboratory must therefore choose from the range of available techniques to maximize the efficiency and accuracy of HLA typing. In this paper we describe a scheme for the accurate determination of all the serologically defined DRB and DQB allotypes using a combination of serology, RFLP analysis and PCR-SSO probing. The efficiencies of serology versus RFLP analysis for the DR typing of 800 individuals, and RFLP analysis versus PCR-SSO probing for the DQB typing of 317 individuals, are compared and the merits of each technique discussed. This scheme, which types for both HLA-DRB and DQB with an accuracy approaching 100%, is now routinely employed in all HLA studies of disease and transplantation in our laboratory.