Human leukocyte antigen non-class II determinants for type 1 diabetes in the Finnish population

We explored the contribution of non-class II HLA loci to type 1 diabetes genetic susceptibility in the Finnish population. We analyzed 11 markers covering a 4-Mb region telomeric to the DQB1 gene in Finnish nuclear families with parents carrying either the DR8-DQB1*04 (n=188) or the DRB1*0404-DQB1*0302 haplotypes (n=135). On the DRB1*0404-DQB1*0302 haplotype we found independent disease association of the D6S273 and C125 markers (p(corr) = 10(-4) and 0.0095, respectively). The C125*200 alleles on this haplotype conferred an increased disease risk (OR = 3.6; p = 0.003). The B*39 allele also showed disease association (OR = 2.6; p = 0.054). The C125*200 allele appeared at an increased frequency also on transmitted B39 positive DRB1*0404-DQB1*0302 haplotypes, suggesting an independent effect. In addition, the C143*417 allele on the DRB1*08-DQB1*04 haplotype was associated with decreased disease risk (OR = 0.48, p = 0.003). Our data confirm that non-class II HLA loci affect genetic susceptibility to type 1 diabetes. In addition to HLA B*39 the C125 locus contributes to disease risk on the Finnish DRB1*0404-DQB1*0302 haplotypes. Another locus close to D6S273 may also have an effect. For the first time we report that a locus near the C143 marker appear to affect disease association of the DRB1*08-DQB1*04 haplotype.     

An additional susceptibility gene for juvenile idiopathic arthritis in the HLA class I region on several DR-DQ haplotypes

Juvenile idiopathic arthritis (JIA) is an HLA-associated rheumatic disease with onset in childhood. We recently reported that allele 5 at microsatellite D6S265 in the HLA class I region is associated with JIA, independent of linkage disequilibrium with the high risk DR8-DQ4 haplotype. In the present study, we investigated whether alleles at D6S265, or other markers in this region, also modify the risk for JIA on other haplotypes, i.e., DRB1*1301-DQB1*0603 or DRB1*1101/4-DQB1*0301. We observed a significant association with allele 6 at D6S265 on the DRB1*1301-DQB1*0603 haplotype. We also noted an association with allele 3 at D6S265, when carried on the DRB1*1101/4-DQB1*0301 haplotype. Our results further support an additional JIA susceptibility gene in the HLA class I region in linkage disequilibrium with alleles at D6S265.     

A gene telomeric of the HLA class I region is involved in predisposition to both type 1 diabetes and coeliac disease

We have recently shown that an as yet unidentified gene within or in the vicinity of the HLA complex, in linkage disequilibrium with microsatellite D6S2223, modifies the risk to develop type 1 diabetes independently of HLA-DR and -DQ genes. This microsatellite is located 2.5 Mb telomeric to HLA-F and particular alleles at this microsatellite modifies the risk encoded by the high-risk DRB1*03-DQA1*0501-DQB1*0201 (hereafter called DR3) haplotype. Coeliac disease and type 1 diabetes share some susceptibility HLA class II haplotypes, in Scandinavia particularly the DR3 haplotype. We therefore investigated whether the marker D6S2223 might also be associated with coeliac disease. In order to keep the contributions from the DRB1-DQA1-DQB1 genes constant (i.e., eliminate the effects of linkage disequilibrium to disease associated DR and/or DQ alleles), we only used cases and controls being homozygous for DR3. We found the frequency of allele 3 at D6S2223 to be reduced among patients with coeliac disease compared to controls, to a similar extent as seen in type 1 diabetes, which could not be explained by a different distribution of HLA-B alleles (as ascertained by typing for the MIB microsatellite). This negatively associated allele 3 at D6S2223 occurred in a homozygous combination at a significantly lower frequency among patients than controls. Thus, allele 3 at D6S2223 on DR3 haplotypes is associated with reduced susceptibility for development of both type 1 diabetes and coeliac disease. This suggests that a gene(s) in the vicinity of D6S2223 is involved in the pathogenesis of both of these immune-mediated diseases.     

Presence of the DRB4*0103102N null allele in different DRB1*04-positive individuals

The DRB4 gene encoding the DR53 antigen is present in DRB1*04-, DRB1*07- and DRB1*09-positive individuals. Eight allelic variants of DRB4 have been recognized, 5 resulting in an expressed DR53 antigen and 3 belonging to the null alleles. So far the DRB4*0103102N null allele had been found exclusively in individuals carrying the haplotype DR7,-DQ9. High-resolution typing of HLA class II by polymerase chain reaction using sequence-specific primers (PCR-SSP) and/or sequence-based typing of kidney patients and their families revealed the presence of the DRB4*0103102N null allele segregating with DRB1*04 and DQB1*03 in 4 different families. Three different haplotypes on which the null allele was located, were recognized by family studies: DRB1*0401, DQB1*0301; DRB1*0402, DQB1*0302 and DRB1*0404, DQB1*0302. Determination of the DR53 specificity of antisera reacting with DR53-positive individuals has always been difficult due to the simultaneous presence of DR4, 7 or 9. Identification of DR4-positive DR53-negative individuals as described here, provided the serological reactions with DR53-antisera and revealed the antibody specificities in the antisera used.     

Extended DR3-D6S273-HLA-B haplotypes are associated with increased susceptibility to type 1 diabetes in US Caucasians

Human leukocyte antigen (HLA)-DR3 haplotypes are associated with susceptibility to type 1 diabetes (T1D). Reports from Northern European populations show that an allele (D6S273*2) at a microsatellite mapping to HLA class III marks an extended DR3-B18 haplotype associated with increased susceptibility to T1D. Consistent with previous reports, D6S273*2 marked a highly predisposing DR3 haplotype in European origin, multiplex families from the USA. Furthermore, we observed on DR3 haplotypes that other D6S273 alleles were also significantly associated with both increased transmission (D6S273*5; P < 0.02) and decreased transmission (D6S273*7; P < 0.05) to affected individuals. The differential transmission was most evident among DR3-B8 haplotypes. Neither HLA-B*1801 nor any alleles of D6S273 were associated with increased T1D predisposition on DR4 haplotypes. These data indicate that multiple alleles of D6S273 mark a susceptibility locus whose effect we were able to detect only among DR3 haplotypes but not limited to DR3-B18 haplotypes.     

HLA associations in type 1 diabetes among patients not carrying high-risk DR3-DQ2 or DR4-DQ8 haplotypes

Type 1 diabetes is a complex disease where numerous genes are involved in the pathogenesis. Genes that account for approximately 50% of the familial clustering of the disease are located within or in the vicinity of the HLA complex on chromosome 6. Some DRB1, DQA1 and DQB1 genes are known to be involved, in addition to as yet unidentified HLA-linked genes. The DR4-DQ8 and DR3-DQ2 haplotypes are known to confer high risk for developing the disease, particularly when occurring together. Approximately 10% of patients, however, do not carry any of these high-risk HLA class II haplotypes. We have performed genotyping of DRB1, DQA1 and DQB1 alleles in non-DR3-DQ2/non-DR4-DQ8 patients and controls from Sweden and Norway to test if any HLA associations were observed in these patients. Our results clearly demonstrate several statistically significant differences in the frequency of HLA haplotypes between patients and controls. Case-control analysis including the relative predispositional effect test, and transmission disequilibrium test (TDT) analysis in Norwegian type 1 diabetes families revealed that the DQA1*03-DQB1*0301, DQA1*0401-DQB1*0402, DQA1*0101-DQB1*0501, DQA1*03-DQB1*0303 and DQA1*0102-DQB1*0604 haplotypes may also confer risk. Our analyses also supported independent risks of certain DRB1 alleles. The study clearly demonstrates that HLA associations in type 1 diabetes extends far beyond the well-known associations with the DR4-DQ8 and DR3-DQ2 haplotypes. Our data suggest that there is a hierarchy of HLA class II haplotypes conferring risk to develop type 1 diabetes.     

Associations of HLA microsatellites with rheumatoid arthritis in Singaporean Chinese

Rheumatoid arthritis in Singaporean Chinese has previously been shown to be associated with the DRB1*0405, DRB1*1001 haplotypes and to the DRB1*0901 haplotype when the former two were removed. The present paper focused on eight HLA associated microsatellite markers (TNFa, TNFd, D6S273, TAP1CA, DQCAR, DQCARII, D6S2222, D6S2223) and their allelic associations with Chinese RA. 60 RA patients and 75 healthy controls were studied. It appeared that DQCARII*194/DRB1*0405/TNFa*117 was part of the extended haplotype predisposed to RA, whereas DRB1*0901/D6S273*128 contributed to susceptibility to RA to a lesser degree in Singaporean Chinese. Additionally, a negative association with DQCAR*186/DRB1*0301/D6S273*122/TNFd*124 was observed. No association with disease development was observed in this study.     

The telomeric part of the HLA region predisposes to rheumatoid arthritis independently of the class II loci

We have evaluated the possible contribution of genes besides DQ and DR to the association of HLA with rheumatoid arthritis (RA). To this end, we have looked at the allele distributions of six microsatellites, D6S1014, D6S2673, TNFalpha, MIB, C1-2-5, and C1-3-2 among 132 RA patients and 254 controls. We have defined 19 microsatellite clusters corresponding to previously described ancestral haplotypes. One of them was D6S1014*143-D6S273*139-TNFalpha*99-MIB*350-C1-2-5*196-C1-3-2*354, often found associated with DQB1*0201-DRB1*0301. As part of this microsatellite cluster, the allele MIB*350 was found to be a RA-predisposing factor, independent of DRB1*0301 and RA-predisposing haplotypes DQB1*03-DRB1*04 and DQB1*0501-DRB1*01. We conclude that the telomeric part of the HLA region contains a locus conferring predisposition to RA independently of HLA class II.     

The distribution of HLA class II susceptible/protective haplotypes could partially explain the low incidence of type 1 diabetes in continental Italy (Lazio region)

HLA class II is the primary susceptibility gene to type 1 diabetes and the analysis of HLA class II association could help to clarify the relative weight of genetic contribution to the incidence of the disease. Here we present an extensive typing for HLA class II alleles and their haplotypes in a homogenous population of type 1 diabetic patients (n=134) and controls (n=128) and in simplex (n=100) and multiplex families (n=50) from continental Italy (Lazio region). Among the various haplotypes tested, the DRB1*0301-DQA1*0501-DQB1*0201 was the most frequent found in type 1 diabetic patients and was transmitted in 82% of affected siblings, whereas DRB1*0402-DQA1*0301-DQB1*0302 appeared to have the highest odds ratio (10.4), this haplotype was transmitted in 96.3% of affected siblings, followed by DRB1*0405-DQA1*0301-DQB1*0302, DRB1*0405-DQA1*0301-DQB1*0201, DRB1*0401-DQA1*0301-DQB1*0302 and DRB1*0404-DQA1*0301-DQB1*0302. The following haplotypes showed a significant decreased transmission to diabetic siblings: DRB1*0701-DQA1*0201-DQB1*0303, DR2-DQA1*01-DQB1*0602, DR5-DQA1*0501-DQB1*0301. We suggest that the HLA DR/DQ haplotype/genotype frequencies observed could in part explain the low incidence of type 1 diabetes registered in Lazio region (8.1/100.000/year), for a number of reasons: i) the low frequency, in the general control population, of the most susceptible haplotypes and genotype for type 1 diabetes DRB1*0301-DQA1*0501-DQB1*0201 (14%), and DR4-DQA1*0301-DQB1*0302 (9%) and DRB1*0301-DQA1*0501-DQB1*0201/DR4-DQA1*0301-DQB1*0302 (0.8%) compared to other countries characterised by high incidence rate of the disease, Sardinia and Finland, respectively; ii) a significant lower ratio, in the control population, between the susceptible DRB1*0301-DQA1*0501-DQB1*0201 and the neutral DRB1*0701-DQA1*0501-DQB1*0201 haplotypes compared to the Sardinian population; iii) the high frequency of protection haplotypes/genotypes as the DR5-DQA1*0501-DQB1*0301, and DR5-DQA1*0501-DQB1*0301/DR5-DQA1*0501-DQB1*0301 very common in the control population of Lazio region and the DRB1*1401-DQA1*0101-DQB1*0503 haplotype.     

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.     

The prevalence of HPA-1a alloimmunization and the potential risk of FNAIT depend on both the DRB3*01:01 allele and associated DR-DQ haplotypes

Alloimmunization against human platelet antigen (HPA)-1a during pregnancy can cause foetal/neonatal alloimmune thrombocytopenia (FNAIT) and severe bleeding in the foetus or newborn and likely depends on several factors. HPA-1a alloimmunization is associated with DRB3*01:01, which is associated with several DR-DQ haplotypes. However, it is not known to what extent these haplotypes contribute to the prevalence of HPA-1a alloimmunization. HPA-1a–alloimmunized women, identified in a prospective study, and random donors were typed for selected DRB3, DRB4, DRB1, DQA1 and DQB1 alleles to determine allele and DR-DQ haplotype frequencies. DRB3*01:01 was carried by 94% HPA-1a–immunized women compared to 27% in the general population. In the first population, the DR3-DQ2 haplotype was overrepresented (P < .003). The prevalence of HPA-1a alloimmunization was estimated to be about twice as frequent with DR3-DQ2 compared to DR13-DQ6, together accounting for about 90% of DRB3*01:01–positive individuals. Further, we examined DQB1*02 and DRB4*01:01 alleles for their reported association with HPA-1a alloimmunization, in the context of DR-DQ haplotypes. Since ~ 80% of DQB1*02 alleles are linked to the DR3-DQ2 haplotype, the association might be coincidental. However, the DQB1*02:02–associated DR7-DQ2 haplotype was also overrepresented in alloimmunized women, suggesting a role for this allele or haplotype in HPA-1a alloimmunization. As DRB4*01:01 is predominantly associated with the DR7-DQ2 haplotype in HPA-1a–alloimmunized individuals, the reported association with FNAIT may be coincidental. Typing for DR-DQ haplotypes revealed important genetic associations with HPA-1a alloimmunization not evident from typing individual alleles, and the presence of different DRB3-associated DR-DQ haplotypes showed different prevalence of HPA-1a alloimmunization.     

HLA DR-DQ-encoded genetic determinants of childhood-onset type 1 diabetes in Finland: an analysis of 622 nuclear families

The diabetes predisposing effect of HLA genes is defined by a complex interaction of various haplotypes. We analyzed the disease association of HLA DRB1-DQA1-DQB1 genotypes in a large nuclear family cohort (n = 622) collected in Finland. Using the affected family based artificial control approach we aimed at characterizing all detectable disease-specific HLA haplotype and genotype effects. The DRB1*0401-DQB1*0302 haplotype was the most prevalent disease susceptibility haplotype in the Finnish population followed by (DR3)-DQA1*05-DQB1*02 and DRB1*0404-DQB1*0302. DRB1*0405-DQB1*0302 conferred the highest disease risk, although this haplotype was very rare. The DRB1*04-DQB1*0304 was also associated with increased disease risk, an effect detected for the first time in the Finnish population. The following haplotypes showed significant protection from the disease and are listed in decreasing order of the strength of their effect: (DR7)-DQA1*0201-DQB1*0303, (DR14)-DQB1*0503, (DR15)-DQB1*0602, DRB1*0403-DQB1*0302, (DR13)-DQB1*0603, (DR11/12/13)-DQA1*05-DQB1*0301, (DR1)-DQB1*0501. In addition to the DRB1*0401/0404-DQB1*0302/(DR3)-DQA1*05-DQB1*02 genotype and DRB1*04-DQB1*0302 homozygous genotypes, heterozygous combinations DRB1*0401-DQB1*0302/(DR13)-DQB1*0604, approximately /(DR8)-DQB1*04, approximately /(DR9)-DQA1*03-DQB1*0303, approximately /(DR1)-DQB1*0501 and approximately /(DR7)-DQA1*0201-DQB1*02 were also disease-associated. As a new finding in this population, the (DR3)-DQA1*05-DQB1*02 homozygous and (DR3)-DQA1*05-DQB1*02/(DR9)-DQA1*03-DQB1*0303 heterozygous genotypes conferred disease susceptibility. Similarly, the DRB1*0401-DQB1*0302/(DR13)-DQB1*0603 genotype was disease predisposing, implying that DQB*0603-mediated protection from diabetes is not always dominant. Comparison of our findings with published data from other populations indicates a significant disease-specific heterogeneity of the (DR8)-DQB1*04, (DR7)-DQA1*0201-DQB1*02 and (DR3)-DQA1*05-DQB1*02 haplotypes.     

HLA-DRB1*0401 IS ASSOCIATED WITH SUSCEPTIBILITY TO INSULIN-DEPENDENT DIABETES MELLITUS INDEPENDENTLY OF THE DQB1 LOCUS

The distribution of DRB1*04 alleles and DRB1/DQB1 haplotypes was analysed in 57 DR4⁺ caucasoid subjects with insulin-dependent diabetes mellitus (IDDM) and 96 DR4⁺ healthy controls selected on the basis of DR serology, and the findings were analysed in relation to age at diagnosis of IDDM. DNA samples were amplified using specific DR and DQ primers and hybridized with sequence-specific oligonucleotide probes. A significantly increased combined frequency of DRB 1*0401 and 0402 was observed in IDDM subjects aged ≤12 years at diagnosis (allele frequency 88.4% compared with 62.0% in controls, P < 0.025). There was a non-significant increase in DRB 1*0401 and 0402 in IDDM subjects ≤12 years when compared with IDDM subjects >12 years (P < 0.1). DRB 1 *0404 was decreased in the total IDDM subject group compared with controls (4.8% vs. 19.0%, P < 0.025) but did not reach statistical significance in the individual age at diagnosis groups. In contrast, the frequency of DQB1 *0302 was increased uniformly across both ages at diagnosis groups. In controls DRB 1*0401 occurred in haplotype association with DQB 1*0301 in a significantly greater frequency than with DQB 1*0302. However, 95.0% of DRB 1*0401 IDDM subjects were DQB 1*0302. DRB 1*0404, which was decreased in frequency in IDDM subjects, occurred in association significantly more frequently with DQB 1 *0302 in controls. These results imply that DRB 1 and DQB 1 have independent roles as HLA susceptibility genes in IDDM. DQB1 may have a permissive role whereas DRB1 could influence the rate at which underlying disease progresses to clinical IDDM.     

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.     

Estimation of diabetes risk in Brazilian population by typing for polymorphisms in HLA-DR-DQ, INS and CTLA-4 genes

The study aimed to further characterise HLA encoded risk factors of type 1 diabetes (T1D) in Brazilian population and test the capability of a low resolution full-house DR-DQ typing method to find subjects at diabetes risk. Insulin and CTLA-4 gene polymorphisms were also analysed. The method is based on an initial DQB1 typing supplemented by DQA1 and DR4 subtyping when informative. Increased frequencies of both (DR3)-DQA1*05-DQB1*02 and DRB1*04-DQA1*03-DQB1*0302 haplotypes were detected among patients. DRB1*0401, *0402, *0404 and *0405 alleles were all common in DQB1*0302 haplotypes and associated with T1D. (DRB1*11/12/1303)-DQA1*05-DQB1*0301, (DRB1*01/10)-DQB1*0501, (DRB1*15)-DQB1*0602 and (DRB1*1301)-*0603 haplotypes were significantly decreased among patients. Genotypes with two risk haplotypes or a combination of a susceptibility associated and a neutral haplotype were found in 78 of 126 (61.9%) T1D patients compared to 8 of 75 (10.7%) control subjects (P < 0.0001). Insulin gene -2221 C/T polymorphism was also associated with diabetes risk: CC genotype was found among 83.1% of patients compared to 69.3% of healthy controls (P=0.0369, OR 1.98) but CTLA-4 gene +49 A/G polymorphism did not significantly differ between patients and controls. Despite the diversity of the Brazilian population the screening sensitivity and specificity of the used method for T1D risk was similar to that obtained in Europe.     

DQCAR microsatellite polymorphisms in three selected HLA class II-associated diseases

Abstract: DQCAR is a very polymorphic CA repeat microsatellite located between the HLA DQA1 and DQB1 gene. Previous studies have shown that specific DQCAR alleles are in tight linkage disequilibrium with known HLA DR-DQ haplotypes. Of special interest was the fact that haplotypes containing long CA repeat alleles (DQCAR > 111) were generally more polymorphic within and across ethnic groups. In these latter cases, several DQCAR alleles were found even in haplotypes containing the same flanking DQA1 and DQB1 alleles. In this work, three HLA class II associated diseases were studied using the DQCAR microsatellite. The aim of this study was to test if DQCAR typing could distinguish haplotypes with the same DRB1, DQA1 and DQB1 alleles in control and affected individuals. To do so, patients with selected HLA DR-DQ susceptibility haplotypes were compared with HLA DR and DQ matched controls. This included: Norwegian subjects with Celiac disease and the HLA DRB1*0301, DQA1*05011, DQB1*02 haplotype; Japanese subjects with Type 1 (insulin-dependent) Diabetes Mellitus and the HLA DRB1*0405, DQA 1*0302, DQB 1*0401 haplotype; and French patients with corticosensitive Idiopathic Nephrotic Syndrome and the HLA DRB 1*0701, DQA 1*0201, DQB1*0202 haplotype. These specific haplotypes were selected from our earlier work to include one haplotype bearing a short DQCAR allele (celiac disease and DR3, DQ2-DQCAR99) and two haplotypes bearing long DQCAR alleles (Diabetes Mellitus and DR4, DQ4-DQCAR 113 or 115 Idiopathic Nephrotic syndrome and DR7, DQ2-DQCAR 111–121). Additional DQCAR diversity was found in both control and patients bearing haplotypes with long CA repeat alleles. The results indicate that DQCAR typing did not improve specificity in combination with high resolution DNA HLA typing as a marker for these three disorders.     

Similar incidence of type 1 diabetes in two ethnically different populations (Italy and Slovenia) is sustained by similar HLA susceptible/protective haplotype frequencies

The incidence of type 1 diabetes (T1DM) seems to depend in part on the population frequencies of susceptible and protective HLA haplotypes. The present study aimed to (i): characterize the genetic susceptibility to T1DM in the Slovenian population, (ii) test the general hypothesis that T1DM incidence is related to the frequencies of susceptible/protective haplotypes, (iii) compare allele, haplotype and genotype frequencies in Slovenians and Italians that represent two white populations with a similar incidence of T1DM (7.9/100,000/year and 8.1/100,000/year, respectively). The haplotype found most frequently among Slovenian T1DM patients was DRB1*0301-DQA1*0501-DQB1*0201 (53%). The DR4-DQA1*0301-DQB1*0302 haplotypes conferring susceptibility to T1DM were those bearing DRB1*0401 (OR = 12), DRB1*0404 (OR = 4.7) and DRB1*0402 (OR = 4.5). Negative associations with the disease were found for the following haplotypes: DRB1*1501-DQA1*0102-DQB1*0602, DRB1*1301-DQA1*0102-DQB1*0603, DRB1*1101/1104-DQA1*0501-DQB1*0301, and DRB1*1401-DQA1*0101-DQB1*0503. Our findings indicate that the low frequencies of susceptible genotypes, in particular, DR3-DQA1*0501-DQB1*0201/DR4-DQA1*0301-DQB1*0302, together with a high frequency of protective haplotypes, could in part explain the low incidence of T1DM in the Slovenian population. The combined frequencies of susceptible genotypes were similar in the two populations (Slovenia = 19.2%, Italy = 17.6%), and the 95% confidence limits of the OR values for each genotype in the two populations overlapped, indicating no significant differences between the values. We conclude that the similar incidences of T1DM in Italian and Slovenian populations are in part a reflection of similar frequencies of HLA susceptible/protective haplotypes.     

The association of specific HLA class I and II alleles with type 1 diabetes among Filipinos

The genetic predisposition to type 1 diabetes among Filipinos was examined by PCR/SSOP HLA class I and II typing of 90 patients and 94 general population controls. The HLA-DRB1, DQB1, and the A, B, and C loci were typed using the reverse SSO probe line-blot method while the DPB1 and DPA1 loci were typed using the SSO probe dot blot method. The Filipino population has a distinctive frequency distribution of HLA class II alleles as well as linkage disequilibrium patterns: a DR-DQ haplotype, unique to Filipinos, contains a DRB1 allele (*0405) positively associated with type 1 diabetes in other populations and DQA1 and DQB1 alleles (*0101-*0503) that are negatively associated in other populations. Specific DR-DQ haplotypes or alleles could be identified as susceptible, neutral or protective based on the distribution among Filipino patients and controls. The DR9 and DR3 haplotypes showed the most dramatic increase among patients (0.156 vs 0.063) and (0.172 vs 0.042), respectively. Among Filipinos, the DR3/9 genotype confers approximately the same risk as the well-known high-risk DR3/4 genotype, similar to that for DR3/3 and DR9/9. The common DR2 haplotype in the Philippines (DRB1*1502-DQB1*0502) was only slightly decreased in type 1 diabetic patients (0.200 in patients vs 0.270 in controls). Another DR2 haplotype, DRB1*1502-DQB1*0501, was significantly decreased among patients. In addition, haplotypes containing DQB1*06 alleles, such as the DRB1*0803-DQB1*0601 (OR = 0.1), are strongly protective. The DR4 allele group was also increased in Filipino patients compared to controls. In this population there is, as in other populations, a hierarchy of type 1 diabetes associations among the many different DR4 haplotypes (n = 15). The high-risk haplotypes in this population are the very rare DRB1*0405-DQB1*0302 and DQB1*0405-DQB1*0201, followed by the more common DRB1*0405-DQB1*0401 and DRB1*0405-DQB1*0402. The DRB1*0403-DQB1*0302 is protective. The DRB1*0405-DQB1*05031 haplotype, which is unique to Filipinos, appears to be "neutral". HLA-DPB1*0202 was significantly increased among patients (0.056 vs 0.011; with OR = 5.3); this increase does not appear to simply reflect linkage disequilibrium with high risk DR-DQ haplotypes. The observed distribution of HLA class II alleles among Filipino patients and controls strongly supports the notion that specific combinations of alleles at the DRB1, DQB1, DQA1, and DPB1 loci are critical in determining the risk for type 1 diabetes. Specific HLA class I alleles also show significant associations with type 1 diabetes in this population. HLA-A*2402 and *2403 were increased among patients; however, 2407 was decreased. Inaddition, A *1101 was significantly decreased among patients (OR = 0.51). Moreover, these HLA-A associations do not appear attributable to linkage disequilibrium with the DR-DQ region. The allele B*5801 was increased in patients while B*1301 was decreased; both of these associations, however, reflected linkage disequilibrium with high-risk and with protective DR-DQ haplotypes, respectively. The HLA-C*0102 and *0302 alleles were increased (0.089 vs 0.037 and 0.122 vs 0.064) while C*1502 and *0702 (0.028 vs 0.080 and 0.217 vs 0.330) were decreased. The observed associations of C*0102 and C*1502 do not simply reflect linkage disequilibrium with high-risk DR-DQ haplotypes. Thus, specific HLA class I-A and C alleles were associated with type 1 diabetes in the Filipinos and may, in combination with high risk DR-DQ haplotypes, significantly modify disease risk.     

HLA class II haplotype associations with inflammatory bowel disease in Jewish (Ashkenazi) and non-Jewish caucasian populations

Ulcerative colitis (UC) and Crohn's disease (CD) are the clinical entities comprising idiopathic inflammatory bowel disease (IBD). Previous studies on the association of IBD and human leukocyte antigen (HLA) class II genes suggested a role for HLA in this disease. Here we present HLA class II (DRB1, DQB1, DQA1, DPB1) allele and haplotype distributions determined using the polymerase chain reaction and sequence-specific oligonucleotide probe methods. A total of 578 UC and CD Caucasian patients and controls from Jewish (Ashkenazi) and non-Jewish populations was examined. Our previously reported association of DR1-DQ5 with CD was attributable to DRB1*0103. A dramatic association with IBD and the highly unusual DRB1*0103-DQA1*0501-DQB1*0301 haplotype (OR = 6.6, p = 0.036) was found. The more common DR1 haplotype, DRB1*0103-DQA1*0101-DQB1*0501, was also associated with IBD (OR = 3.1, p = 0.014), a result suggesting that interaction between DR and DQ may determine the extent of disease risk. Our previously reported association of DR2 with UC was attributable to DRB1*1502 (OR = 2.6, p = 0.006). At the DPB1 locus, a significant association of DPB1*0401 with CD was observed for the combined populations (OR = 1.85, p = 0.007). These observations indicate that some class II alleles and haplotypes confer susceptibility to both UC and CD, implying common immunogenetic mechanisms of pathogenesis, while others confer risk to only one of these diseases, and illustrate the value of DNA HLA typing in disease susceptibility analyses.     

Response to hepatitis B vaccine: multiple HLA genes are involved

Abstract: The mechanism underlying the impaired immune response to hepatitis B vaccines in up to 10% of healthy subjects is not known. An increased incidence of poor responsiveness in subjects with HLA- DR3 ⁺ or - DR7 ⁺ haplotypes has been documented, suggesting that HLA-DR-linked genes may regulate the human response to hepatitis B surface antigen. However, not all BLA-DR3 ⁺ and/or - DR7 ⁺ individuals are poor responders, and subjects with identical HLA-DR haplotypes sometimes display totally divergent antibody responses to vaccination. HLA class II DNA typing was performed in well and poorly responding hepatitis B vaccine recipients and we analyzed the role of the single HLA-DR, -DP, and -DQ molecules and of their associated (interaction) haplotypes in the response to hepatitis B vaccination. Statistical analysis revealed that HLA-DRBl*010*, - DR5 , -DPBl*040*, -DQBl*0301, and -DQBl*0501 were more abundant in good responders, whereas HLA-DRB1*07, -DPBl*1101, and -DQBl*020* were associated with poor response, with DQBl*020* showing the strongest association with poor responsiveness. We further investigated whether there were interactions between the HLA factors contributing to poor responsiveness. We show here that HLA-DPB1*02 was negatively associated with responsiveness when it occurred in association with haplotype DRBl*0701/ DRB4*0101-DQBl*020*, and DRB4*0101 was negatively associated with responsiveness when it occurred in association with haplotype DRB1*0301/ DRB3*0101-DQBl*020*. Our results indicate that the immune response to hepatitis B vaccine is largely determined by HLA-DR, -DP, and -DQ genes and that interaction between HLA molecules that are not in linkage disequilibrium contributes to poor responsiveness.