A population- and family-based study of Canadian families reveals association of HLA DRB1*0103 with colonic involvement in inflammatory bowel disease

The aim of this study was to identify major histocompatibility complex alleles associated with the development and clinical features of inflammatory bowel disease (IBD). Genotyping at the human leukocyte antigen (HLA) DRB1 and DQB1 loci was performed on individuals from 118 Caucasian IBD sibling pair families and on 216 healthy controls. Both population- and family-based association tests were used to analyze data obtained on the entire study population and on clinical subgroups stratified by diagnosis, ethnicity, and disease distribution. HLA DRB1*0103 was significantly associated with IBD (OR = 6.0, p = 0.0001) in a case-control analysis of non-Jewish IBD-affected individuals. This association was apparent among both Crohn's disease (OR = 5.23, p = 0.0007) and ulcerative colitis (OR = 7.9, p = 0.0001) patients and was confirmed in the non-Jewish IBD population by results of family-based association analysis using the transmission disequilibrium test. HLA DQB1*0501 was also associated with IBD (OR = 1.64, p = 0.02) in the non-Jewish population. but statistically significant association of this allele with disease was not detected for Crohn's disease and ulcerative colitis separately. No significant associations were identified among the Jewish patients. In the non-Jewish IBD families, IBD was as strongly associated with the DRB1*0103 DQB1*0501 haplotype as with the DRB1*0103 allele alone. The carrier frequency of the DRB1*0103 allele was found to be 10-fold higher in Crohn's disease patients with pure colonic involvement than in healthy controls (38.5% vs. 3.2%; p = 0.0002). These data demonstrate the association of the HLA DRB1*0103 allele with both Crohn's disease and ulcerative colitis and with large intestine-restricted disease in non-Jewish IBD patients and therefore identify HLA DRB1*0103 as a potentially important contributor to disease susceptibility and to expression of colonic involvement in IBD.     

Analysis of MHC class II DP, DQ and DR alleles in Crohn's disease

BACKGROUND: Although inflammation in Crohn's disease is believed to be mediated by activated T cells, genotyping of all MHC class II alleles in white people with this disease has not been reported. AIMS: To perform a detailed molecular analysis of HLA DPB, DQB, and DRB genes in white patients with Crohn's disease and controls in order to determine if the inheritance of any class II genes confers susceptibility or resistance to this disease. METHODS: Complete molecular typing of HLA class II DPB, DQB, and DRB alleles was performed in 58 white patients with Crohn's disease and 93 healthy controls using a polymerase chain reaction-sequence specific oligonucleotide based approach. RESULTS: No significant association with any DPB or DQB alleles was noted in patients with Crohn's disease. Since our previous studies had shown a strong association of an HLA DRB3*0301/DRB1*1302 haplotype with Crohn's disease, we re-examined this association using more stringent genotyping criteria. This haplotype was present in 20.7% of patients and 5.4% of controls (p = 0.0066; relative risk = 4.59). CONCLUSIONS: The DRB3*0301/DRB1*1302 haplotype is the only significant MHC class II association noted in white people with Crohn's disease and represents the strongest association of any MHC or non-MHC locus with this disease.     

An increased risk of Crohn's disease in individuals who inherit the HLA class II DRB3*0301 allele.

The role of inflammatory T cells in Crohn's disease suggests that inherited variations in major histocompatibility complex (MHC) class II genes may be of pathogenetic importance in inflammatory bowel disease. The absence of consistent and strong associations with MHC class II genes in Caucasian patients with inflammatory bowel disease probably reflects the use of less precise typing approaches and the failure to type certain loci by any means. A PCR-sequence-specific oligonucleotide-based approach was used to type individual alleles of the HLA class II DRB1, DRB3, DRB4, and DRB5 loci in 40 patients with ulcerative colitis, 42 Crohn's disease patients, and 93 ethnically matched healthy controls. Detailed molecular typing of the above alleles has previously not been reported in patients with inflammatory bowel disease. A highly significant positive association with the HLA-DRB3*0301 allele was observed in patients with Crohn's disease (P = 0.0004) but not in patients with ulcerative colitis. The relative risk for this association was 7.04. Other less significant HLA class II associations were also noted in patients with Crohn's disease. One of these associations involved the HLA-DRB1*1302 allele, which is known to be in linkage disequilibrium with HLA-DRB3*0301. These data suggest that a single allele of an infrequently typed HLA class II locus is strongly associated with Crohn's disease and that MHC class II molecules may be important in its pathogenesis.     

Inflammatory bowel disease: progress toward a gene.

The pathogenesis of ulcerative colitis (UC) and Crohn's disease (CD) is still unknown, but the importance of genetic susceptibility has been clearly shown by epidemiological data from family and twin studies. Linkage studies have identified two susceptibility loci for inflammatory bowel disease (IBD) on chromosomes 12 and 16. Importantly, these linkages have been replicated by independent investigators, and studies of positional candidates within these regions continue, together with fine mapping strategies. Regions of 'suggestive' linkage on chromosomes 1, 3, 4, 6, 7, 10, 22 and X have also been reported in individual studies. Other important candidate genes investigated include the interleukin-1 receptor antagonist, MUC3 and genes of the human leukocyte antigen (HLA) system. The apparently conflicting data in different studies from around the world may be explained by ethnic differences, case mix and genetic heterogeneity. Replicated class II HLA associations include HLA DRB1*0103 and DR2 (DRB1*1502), involved in UC susceptibility, and HLA DRB1*03 and DR4 as resistance alleles for CD and UC respectively. Animal studies have provided insights from targeted mutations and quantitative trait locus analysis. The goals of continuing research include narrowing the regions of linkages and analysis of candidate genes, and possibly the application of newly developed methods using single nucleotide polymorphisms. Advances in IBD genetics hold the potential to provide knowledge about the disease pathogenesis at the molecular level, with ensuing benefits for clinical practice.     

Association of hla–dr4-dw15 (drb1*0405) and dr10 with rheumatoid arthritis in a spanish population

Objective. To analyze the associations of HLA class II antigens with rheumatoid arthritis (RA) in a Spanish population. Methods. We used DNA oligotyping to determine DR types, DQA1 and DQB1 alleles, and DR4 variants in 70 unrelated seropositive RA patients and 189 healthy controls living in Spain. Results. A significantly higher frequency of DR4 was seen in RA patients compared with controls (relative risk [RR] = 2.40). The DR10 specificity correlated most strongly with disease susceptibility (RR = 3.84). A significant decrease in the frequency of DR7 was observed in the RA patients (RR = 0.48). DR4-Dw15 (DRB1*0405) was found to be the unique DR4 allele associated with RA (RR = 4.27, P < 0.05), whereas Dw4 (DRB1*0401) and Dw14 (DRB1*0404/0408) showed no association, and both D10 (DRB1*0402) and Dw13 (DRB1*0403/0407) were negative risk factors for the disease. Approximately one-third of the cases of RA could not be explained by the “shared epitope” hypothesis. Investigation of the DQ alleles associated with DR4 showed that the haplotype Dw15-DQ8 (DRB1*0405-DQB1*0302) was a susceptibility factor for RA (RR = 6.36, P < 0.05). Conclusion. Our results suggest that HLA class II alleles involved in RA susceptibility can vary among different Caucasian populations.     

Amino Acid Polymorphism at Residue 71 in HLA-DR Beta Chain Plays a Critical Role in Susceptibility to Ulcerative Colitis

The association of ulcerative colitis withdistinct HLA-DRB1 alleles has not been easy toascertain. Recent studies show that among HLA-DR2alleles, DRB1*15 but not DRB1*16, is associated with thedisease. Similarly, in the HLA-DR1 group, only DRB1*0103is increased in ulcerative colitis patients. The aim ofour study was to identify critical DRB1 residues thatmight account for these differences. We typed 121 patients with ulcerative colitis and 275controls using gene amplification and sequence-specificoligonucleotide probing for HLA-DRB1 and DRB3. Weobserved a strong negative association between HLA-DRB1 alleles that encode lysine at position 71 intheir -chain and susceptibility to ulcerativecolitis. Differences in the prevalence among otheralleles differing only in the third hypervariable region suggested a hierarchy of susceptible andprotective class II alleles related to the presence ofan acidic, neutral, or basic amino acid residue atposition 71. These data implicate most strongly theamino acid residues in the third hypervariable regionof the DR chain, especially DR71, in theassociation between ulcerative colitis and HLA. However,this does not exclude the contribution of other parts of the molecule and otherimmunoregulatory genes.     

The incidence of HLA DRB1*0103 in ulcerative colitis patients in north-eastern Poland

BACKGROUND/AIMS: Susceptibility to inflammatory bowel disease is partially genetically determined and the HLA (human leukocyte antigen) alloantigens and genes located in the HLA region have been studied over the course of many years as the candidate genes responsible for ulcerative colitis. Improvements in molecular genotyping have allowed disease association with HLA to be narrowed down to specific subtypes. For class II antigens, increasing phenotype frequency of DRB1*0103, DRB1*1502 is observed and positive correlation to disease susceptibility is proposed. We investigated the incidence of HLA DRB1*0103 in ulcerative colitis patients in North-Eastern Poland and possible association with overall disease susceptibility and clinical course of the disease. METHODOLOGY: 41 patients and 45 healthy control blood donors were included in this study. All subjects were Polish. RESULTS: The incidence of HLA DRB1*0103 was low (2.44%), but was associated with fulminant course of the disease (pancolitis with megacolon toxicum). None of the ethnically matched healthy control blood donors possessed the HLA DRB1*0103 allele (0.00%). CONCLUSIONS: The results gained in the presented study confirm, that in the Polish population HLA DRB1*0103 allele is uncommon and it would not be a useful marker of disease susceptibility.     

HLA-DR-DQ haplotypes and genotypes in Finnish patients with rheumatoid arthritis

OBJECTIVES: To elucidate the contribution of HLA-DR-DQ haplotypes and their genotypic combinations to susceptibility to rheumatoid arthritis, and to evaluate the various models for HLA associated risk for the disease in a series of Finnish patients. METHODS: 322 Finnish patients with rheumatoid arthritis were typed for common north European HLA-DR-DQ haplotypes and compared with a series of 1244 artificial family based control haplotypes. RESULTS: The association of the so called shared epitope (SE) haplotypes (DRB1*0401, *0404, *0408, and *01) with rheumatoid arthritis was confirmed. The DRB1*0401 haplotypes carried a far stronger risk for the disease than the (DRB1*01/10)-(DQA1*01)-DQB1*0501 haplotypes. Seven protective HLA haplotypes--(DRB1*15)-(DQA1*01)-DQB1*0602; (DRB1*08)-(DQA1*04)-DQB1*04; (DRB1*11/12)-DQA1*05-DQB1*0301; (DRB1*1301)-(DQA1*01)-DQB1*0603; (DRB1*1302)-(DQA1*01)-DQB1*0604; (DRB1*07)-DQA1*0201-DQB1*0303; and (DRB1*16)- (DQA1*01)-DQB1*0502--were identified. In accordance with the reshaped shared epitope hypothesis, all the protective DRB1 alleles in these haplotypes share either isoleucine at position 67 or aspartic acid at position 70 in their third hypervariable region motif. However, differences in the disease risk of haplotypes carrying the same DR but different DQ alleles were also found: (DRB1*07)-DQA1*0201-DQB1*0303 was protective, while (DRB1*07)-DQA1*0201-DQB1*02 was neutral. The same haplotypes carried different risks for rheumatoid arthritis depending on their combination in genotypes. CONCLUSIONS: When assessing the influence of HLA genes on the susceptibility to rheumatoid arthritis, not only should the HLA-DR or -DQ alleles or haplotypes be unravelled but also the genotype. The effect of HLA class II region genes is more complicated than any of the existing hypotheses can explain.     

HLA-DRB1*1502 confers susceptibility to ulcerative colitis,but is negatively associated with its intractability: a Korean study

BACKGROUND AND AIMS: Several studies have documented the high incidence of several HLA class II alleles in Japanese patients with ulcerative colitis (UC). Although the characteristics of the HLA system in Koreans are quite similar to those in the Japanese, it is not clear whether the HLA pattern in Korean UC is similar to that in Japanese UC. We investigated an association between HLA class II genes and UC patients and the clinical meaning of these genes in Korea. PATIENTS AND METHODS: Unrelated Korean patients with UC ( n=70) and ethnically matched unrelated controls ( n=182) were genotyped for HLA-DR by PCR followed by reverse hybridization using sequence-specific oligonucleotide probes. The clinical characteristics of the patients were analyzed with regard to anti-neutrophil cytoplasmic antibody (ANCA) status and total colectomy for intractability. RESULTS: HLA-DR2 and DRB1*1502 were found significantly more frequently in patients (42.9% and 21.4%) than controls (20.3% and 5.5%). DRB1*1502 was more frequent in p-ANCA-positive (5/23) than in p-ANCA-negative (1/11) patients. Total colectomy for intractability was performed more commonly in patients without DRB1*1502 (14/55) than in those with it (0/15). CONCLUSIONS: Our data are consistent with those of Japanese studies in that DR2 and DRB1*1502 are positively associated with UC patients. In contrast to the Japanese study, however, our results demonstrates that DRB1*1502 is negatively associated with the risk of colectomy in Korean patients with UC.     

HLA antigens and anti-neutrophil cytoplasmic antibodies (ANCA) in inflammatory bowel disease.

HYPOTHESIS AND OBJECTIVES: the hypothesis of this study is that genes involved in the regulation of the immune system, expressed by HLA antigens and anti-neutrophil cytoplasmic antibodies (ANCA), could be determinants of disease susceptibility and behavior in inflammatory bowel disease (IBD). MATERIAL AND METHOD: seventy patients with a diagnosis of inflammatory bowel disease, 46 with ulcerative colitis and 24 with Crohn"s disease were included. HLA class I (A and B) and II (DR) antigens were studied by serological techniques. Detection of ANCA was carried out in all patients by an indirect immunofluorescence method. The relative frequencies of HLA antigens were compared with a control group made up of 156 blood donors. The control group for the ANCA study was made up of 100 individuals. RESULTS: we found a significant increased frequency of HLA-DR2 in patients with ulcerative colitis. No significant differences were found between patients with Crohn"s disease and controls regarding HLA typing. We detected a significant increase of HLA-DR3 in extensive forms of ulcerative colitis. Detection of ANCA was positive in 46% of the patients with ulcerative colitis and in 12% of the patients with Crohn"s disease (p <0.05). We observed an increased frequency of ANCA in patients with UC and HLA-DR2 (p = 0.15). CONCLUSIONS: the association found between HLA-DR3 and extensive forms of ulcerative colitis provides evidence of genetic heterogeneity. The relationship between ANCA and HLA phenotype (although not significant) supports this concept.     

Primary sclerosing cholangitis in two brothers: report of a family with special emphasis on molecular HLA and MICA genotyping

Immune mechanisms play a role in the pathogenesis of primary sclerosing cholangitis (PSC), as suggested by its association with certain HLA haplotypes. Genetic predisposition is supported by its occurrence in families, but data are scarce. Our aim is to report on two brothers with PSC, and to investigate HLA and MICA alleles in this family. The clinical, biochemical, radiological, and pathological findings in two brothers with PSC as well as in their sister and parents were reviewed. Molecular genotyping of HLA class II and MICA alleles was performed in all five family members. In two brothers, p-ANCA positive PSC was found. The youngest also had ulcerative colitis, and had evolved into cirrhosis at the age of 17 years. Their mother had positive p-ANCA and mild cholestatic changes. Their father and sister were unaffected. Both brothers were homozygous for the MICA*00801 allele, and were positive for the susceptibility HLA haplotypes DR3-DQ2 and DR6-DQ6. Their unaffected father and sister both carried the protective DR4 allele. The presence of PSC in two brothers, and the distribution of HLA haplotypes and MICA alleles, adds supportive evidence for an immunogenetic origin of PSC.     

Genetic analysis of the HLA region of Japanese patients with type 1 autoimmune hepatitis

BACKGROUND/AIMS: Genetic predisposition to type 1 autoimmune hepatitis (AIH) is linked mainly to HLA-class II genes. The aim of this study is to scan the HLA region for additional genes which may contribute to type 1 AIH susceptibility. METHODS: We performed association analysis using HLA class I and II alleles and 18 polymorphic microsatellite markers distributed throughout the HLA region. We specifically assessed tumor necrosis factor (TNF)-alpha gene polymorphisms. RESULTS: The frequencies of HLA-DRB1*0405, DRB4 and DQB1*0401 alleles were significantly higher in AIH patients. The association study revealed the presence of three segments in the HLA region showing significantly low P (Pc) values. The first segment was located around the HLA-DR/-DQ subregion, the second was around the HLA-B54 allele, and the third was around two microsatellites near the TNF gene cluster. However, stratification analysis for the effect of DRB1*0405 eliminated association of the latter two segments. Haplotype D of the TNF-alpha promoter gene polymorphisms was weakly associated with susceptibility, but was found to be not significant after stratification analysis. CONCLUSIONS: The most influential gene on type 1 AIH pathogenesis in Japanese is the HLA-DRB1. Other genes in the HLA region, including TNF-alpha, have little or no association with type 1 AIH susceptibility.     

Clinical phenotype is related to HLA genotype in the peripheral arthropathies of inflammatory bowel disease

BACKGROUND & AIMS: The detection of phenotype-determining genes as opposed to disease susceptibility genes requires precise phenotypic characterization of patients. Peripheral arthropathies in inflammatory bowel disease (IBD) are well recognized and are classified with the HLA-B*27-related spondyloarthropathies by the European Spondyloarthropathy Study Group. However, previous HLA studies in IBD have only shown this association with axial disease rather than peripheral arthropathy. We recently reported a clinical classification that describes 2 types of peripheral arthropathy, distinguished by their natural history and articular distribution. We now report the results of immunogenetic studies in these patients and compare them with other spondyloarthropathies. METHODS: IBD patients with type 1 (n = 57) and type 2 (n = 45) peripheral arthropathy were identified by case note review and questionnaire. Patients and 603 controls from Oxfordshire were assigned HLA-A, -B, -C, -DR, and -DQ genotypes by sequence-specific primer polymerase chain reaction. Patient results were compared with controls (corrected for multiple comparisons), then with each other in light of existing hypotheses. The results were compared with those of a cohort of 30 patients with postenteric reactive arthritis (ReA) and 16 patients with IBD-associated ankylosing spondylitis (IBD-AS). RESULTS: Type 1 arthropathy was associated with HLA-DRB1*0103 (DR103; a rare subtype of DR1) in 33% (P < 0.0001; relative risk [RR], 12.1), B*35 in 30% (P = 0.01; RR, 2.2), and B*27 in 26% (P = 0. 001; RR, 4.0). In contrast, type 2 was associated with HLA-B*44 in 62% (P = 0.01; RR, 2.1). Similar significant associations to type 1 arthropathy were found in ReA, except that the HLA-B*27 association was significantly stronger and an association was found with DRB1*0101 (DR1) in 43% (P = 0.001; RR, 2.2). IBD-AS was associated only with HLA-B*27 and DRB1*0101. CONCLUSIONS: These data suggest that the clinical classification into type 1 and type 2 arthropathies describes immunogenetically distinct entities and establish that in polygenic disorders, genes may determine clinical phenotype without conferring overall disease susceptibility (in this case, HLA genes). Type 1 arthropathy is clinically and immunogenetically similar to the spondyloarthropathies, but different HLA associations may define phenotypically distinct groups. Type 2 arthropathy has different HLA associations and may have a different etiology. Further studies are now required to confirm these associations and to elucidate the different pathogenetic mechanisms.     

Pancolitis and genetic markers in the Spanish population.

BACKGROUND: although the etiology of ulcerative colitis disease remains an enigma, the importance of the major histocompatibility complex genes has been described, as in many other autoimmune diseases. AIM: we investigated the contribution of HLA-DRB1, DQA1 and DQB1 genes (HLA region) in patients with pancolitis. METHODS: we studied a total of 89 patients diagnosed as having ulcerative colitis (34 pancolitis and 55 left colitis) and 275 healthy control subjects. Complete information on sex, age, family history, age of onset, localization, complications, surgery and treatment was obtained from all patients. DNA was extracted from peripheral blood leukocytes and all individuals were HLA-DRB1 genotyped. RESULTS AND CONCLUSIONS: there was an association between pancolitis and the presence of DR4-Val86 (p = 0.009; OR = 3.3) and DRB1*0103 (p = 0.02; OR = 5.1) alleles. In patients with left colitis an association with DRB1*1501 (p = 0.03; OR = 1.9) and DRB1*0103 alleles (p = 0.03; OR = 3.8) was observed. We conclude that a strong association between DR4-Val86 and pancolitis exists.     

MHC class II alleles in Mexican patients with rheumatic heart disease

BACKGROUND: Rheumatic heart disease (RHD) is an autoimmune sequel of group A streptococcal infection that has been associated with the presence of some major histocompatibility complex (MHC) genes. Thus, the aim of the present study was to investigate the role of class II alleles in the genetic susceptibility to RHD in Mexican patients and establish the relationship of these alleles with the pattern of valve damage. METHODS: HLA-DR, -DQA1 and -DQB1 allele frequencies were determined by PCR-SSO reverse dot blot and PCR-SSP in 98 Mexican Mestizo patients with RHD and 99 healthy controls. Patients were divided into mitral valve damage (n=46), multivalvular lesion (n=49) and aortic damage (n=3). RESULTS: RHD patients presented an HLA-DR16 increased frequency (pC=0.009, OR=3.9) and a decreased HLA-DR11 frequency (pC=0.018) when compared to healthy controls. HLA-DR16 subtyping showed that DRB1*1602 was the DR16 allele increased in patients (pC=0.007, OR=5.3). Haplotype analysis showed increased frequency of DR16-DQA1*0501-DQB1*0301 in RHD patients when compared to healthy controls (pC=0.011). HLA-DR16 frequency remained significantly increased on patients with multivalvular lesion (pC=0.004, OR=4.8). CONCLUSIONS: Our data suggest an important participation of Amerindian autochthonous HLA-DR16 (DRB1*1602) allele and DR16-DQA1*0501-DQB1*0301 haplotype as markers for RHD genetic susceptibility in the Mexican Mestizo population. HLA-DR16 allele could also play an important role in determining the pattern of valve damage on these patients.     

IBD1 and IBD3 determine location of Crohn's disease in the Spanish population

BACKGROUND: Crohn's disease is a heterogeneous disease from both genetic and clinical points of view. AIMS: To look for associations between distinct genetic polymorphisms and clinical subgroups of the disease. SUBJECTS: A total of 210 patients and 343 healthy control subjects, all adult, unrelated, white, Spanish individuals. METHODS: DNA was purified from peripheral blood samples and was typed by sequence-specific oligonucleotide polymerase chain reaction (PCR) method for human leukocyte antigen (HLA)-DRB1 alleles (IBD3) and by allele-specific PCR for NOD2/CARD15 (IBD1) polymorphisms. RESULTS: NOD2/CARD15 mutations and HLA-DRB1*07 confer susceptibility only to the ileal location of the disease, whereas HLA-DRB1*0103 is associated only with the colonic location of the disease. The IBD3 effect was overshadowed by IBD1 mutations when present. CONCLUSION: The studied genetic polymorphisms of Crohn's disease basically determine the location of the disease and, only secondarily, the clinical form of the disease. This appears to be true for both inflammatory bowel diseases as HLA-DRB1*0103 is associated both with colonic Crohn's disease and ulcerative colitis.     

Histocompatibility leucocyte antigens and closely linked immunomodulatory genes in autoimmune thyroid disease

OBJECTIVES: Associations between autoimmune thyroid disease and antigens of the major histocompatibility complex (MHC) have long been recognized. Graves' disease (GD) is associated with the histocompatibility leucocyte antigen (HLA) haplotype A*01-B*0801-DRB1*0301-DQA1*0501-DQB1*0201 (or B8/DR3) whereas autoimmune hypothyroidism (AIH) has been weakly associated with HLA DRB1*03, *04 and *11/*12 alleles (or DR3, DR4 and DR5). However, the presence of important immunoregulatory genes within the HLA Class II and III regions raises the possibility that these genes harbour the primary susceptibility locus. This study examines genetic variation across the MHC in UK Caucasoid subjects with autoimmune thyroid disease. PATIENTS AND METHODS: DNA extracted from venous blood samples from 215 patients with autoimmune thyroid disease (GD 135, AIH 77) and 267 control subjects was analysed. Genotyping was performed using polymerase chain reaction and sequence specific primers for HLA Class I and II alleles and polymorphisms within the TAP1, TAP2, tumour necrosis factor (TNF), lymphotoxin alpha (LTalpha), heat shock protein (HSP)70-1, HSP70-2 and HSP70-Hom genes. RESULTS: For GD, the strongest association was with DRB1*03 [56% patients positive vs. 24% controls, P = 2 x 10(-10), odds ratio (OR) 4.0]. Positive associations were also seen for DRB1*03 linked alleles, B*0801, DRB3*01/02, DQA1*05, DQB1*02 and DPB1*0101 (OR 2.3-3.4). Specific TNF and LTalpha alleles were strongly associated with GD (Pc = 3 x 10(-5) and 0.001) and weak associations were seen for HSP70-1 + 190C and HSP70-2 + 1267G polymorphisms (Pc = 0.05 and 0.01). These associations were not significant when DRB1*03 status was considered. Patients with AIH showed only a weak association with DQB1*03 (P = 0.02). CONCLUSIONS: These results show that, of the polymorphisms tested within the MHC, GD is most strongly associated with DRB1*03, and associations with other immunoregulatory genes previously described in Caucasian subjects most likely reflect linkage disequilibrium. AIH differs from GD, being less influenced by the MHC region.     

HLA and susceptibility to juvenile idiopathic arthritis: a study of affected sibpairs in an isolated Finnish population

OBJECTIVE: To determine the effects of class I (A, B, and C) and II (DRB1 and DQB1) HLA loci alleles and DRB1-DQB1 haplotypes on genetic susceptibility to juvenile idiopathic arthritis (JIA) in families with 2 or more affected siblings. METHODS: A total of 83 affected siblings belonging to 38 families and corresponding to 50 affected sibpairs, their parents, and 45 healthy sibs were typed for HLA in A, C, B, DRB1, and DQB1 loci. Two study designs were used to explore linkage and association: a case-population control design and a family design using the linkage method: identical-by-descent (IBD) allele-sharing and the association analysis methods. Associations in family data were analyzed using the independent transmission disequilibrium test (TDT) for linkage in the presence of association. This was supplemented by the family-based association test (FBAT) to look for association in the presence of linkage, and is robust for population stratification and phenotype-based selection of data. RESULTS: Significantly increased HLA allele frequencies among the affected siblings compared to Finnish bone marrow donors were observed for HLA alleles Cw4 (odds ratio, OR, 1.7), B27 (1.8), B35 (1.7), and DR8 (3.7). The observed ratio of sharing 0, 1, and 2 HLA haplotypes (A, C, B, DRB1, and DQB1) among affected sibpairs (ASP) was 10:23:17, significantly different from expected (p < 0.001), using a formula that takes into account disease prevalence and the sibling recurrence risk. In the univariate association analysis, both independent TDT and FBAT found significantly increased transmission of the DRB1*0801 and DQB1*0402 alleles and Cw*0401. Independent positive allele effects of Cw*0401, DRB1*0801, and DQB1*0402 as well as negative effects of Cw*0701 and DQB1*0302 were shown by the family-based association analysis of the joint allele main effects. Multi-allelic test for association of each locus confirmed significant associations of the DRB1 and DQB1 loci in the risk of JIA. We found DRB1*0801/DQB1*0402 haplotype to be strongly associated (p < 0.001) with JIA, supporting findings of the haplotype associations-based ASP design. CONCLUSION: Both linkage analysis of the affected sibpairs and association analysis of nuclear families with JIA provided overwhelming evidence of the major contribution of HLA to genetic susceptibility to JIA. The association analysis of HLA-A, C, B, DRB1, and DQB1 alleles by both TDT and FBAT tests confirmed in the Finnish population that the most significant associations prevailed for DRB1*0801, DQB1*0402, as expected from previous observations, and supported the independent role of Cw*0401.     

Extreme genetic risk for type 1A diabetes

Type 1A diabetes (T1D) is an autoimmune disorder the risk of which is increased by specific HLA DR/DQ alleles [e.g., DRB1*03-DQB1*0201 (DR3) or DRB1*04-DQB1*0302 (DR4)]. The genotype associated with the highest risk for T1D is the DR3/4-DQ8 (DQ8 is DQA1*0301, DQB1*0302) heterozygous genotype. We determined HLA-DR and -DQ genotypes at birth and analyzed DR3/4-DQ8 siblings of patients with T1D for identical-by-descent HLA haplotype sharing (the number of haplotypes inherited in common between siblings). The children were clinically followed with prospective measurement of anti-islet autoimmunity and for progression to T1D. Risk for islet autoimmunity dramatically increased in DR3/4-DQ8 siblings who shared both HLA haplotypes with their diabetic proband sibling (63% by age 7, and 85% by age 15) compared with siblings who did not share both HLA haplotypes with their diabetic proband sibling (20% by age 15, P < 0.01). 55% sharing both HLA haplotypes developed diabetes by age 12 versus 5% sharing zero or one haplotype (P = 0.03). Despite sharing both HLA haplotypes with their proband, siblings without the HLA DR3/4-DQ8 genotype had only a 25% risk for T1D by age 12. The risk for T1D in the DR3/4-DQ8 siblings sharing both HLA haplotypes with their proband is remarkable for a complex genetic disorder and provides evidence that T1D is inherited with HLA-DR/DQ alleles and additional MHC-linked genes both determining major risk. A subset of siblings at extremely high risk for T1D can now be identified at birth for trials to prevent islet autoimmunity.