title: Modifying effect of HLA haplotypes located trans to DQB1*02-DRB1*03 in celiac patients of Southern Europe.
abstract: The DQ2 heterodimer, encoded by the human leukocyte antigen (HLA)-DQA1*05-DQB1*02 alleles, is the major genetic susceptibility factor for celiac disease (CD). However, the risk associated to HLA alleles varies among populations. While DRB1*03 is almost the only CD susceptibility allele in Northern Europe with a homozygote frequency of around 30%, CD in south European countries is also associated with the DRB1*07, and DRB1*03 homozygotes patients are rare. Some authors have suggested that DQB1*02-DRB1*03/DQB1*02-DRB1*03 and DQB1*02-DRB1*03/DQB1*02-DRB1*07 may confer different risk susceptibility to CD. This hypothesis, however, has not been demonstrated in a recent family-based study carried out in Finland, suggesting that the proposed differences in risk may be secondary to stratification burdens of case-control studies. To assess this issue, we have investigated the effect of different haplotypes carried trans to DQB1*02-DRB1*03 as additional factors for CD in Spain, using two statistical approaches, a case-control study and a family-based study. We found that DQB1*02-DRB1*03/DQB1*02-DRB1*03 and DQB1*02-DRB1*03/DQB1*02-DRB1*07 were the only combinations that showed a strong and independent association to CD. We did not observe any difference in susceptibility risk conferred by DQB1*02-DRB1*03 and DQB1*02-DRB1*07 when carried trans to DQB1*02-DRB1*03, suggesting that variation in HLA haplotype frequencies among populations may not represent real differences in risk to CD development. We also confirmed a gene dosage effect of the DQB1*02-DRB1*03 haplotype estimating that DQB1*02 homozygotes are at fivefold increased risk for CD compared with DQB1*02 heterozygotes. This risk is conferred by the second copy of the DQB1*02 allele and it seems to be independent of the DQA1.
authors.affiliation: Department of Genetics, Hospital Virgen del Camino, Navarra, Spain.
authors.forename: B
authors.initials: B
authors.lastname: Hernández-Charro
authors.forename: E
authors.initials: E
authors.lastname: Donat
authors.forename: I
authors.initials: I
authors.lastname: Miner
authors.forename: E
authors.initials: E
authors.lastname: Aranburu
authors.forename: F
authors.initials: F
authors.lastname: Sánchez-Valverde
authors.forename: M A
authors.initials: MA
authors.lastname: Ramos-Arroyo
mesh_terms: D016022:Case-Control Studies; D002446:Celiac Disease / Q000235:genetics* / Q000276:immunology*; D005260:Female; D018628:Gene Dosage; D005787:Gene Frequency; D005816:Genetic Complementation Test; D020022:Genetic Predisposition to Disease; D006680:HLA Antigens / Q000235:genetics*; D006683:HLA-DQ Antigens / Q000235:genetics*; D059866:HLA-DQ beta-Chains; D006684:HLA-DR Antigens / Q000235:genetics*; D059811:HLA-DRB1 Chains; D006239:Haplotypes; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D008297:Male; D012307:Risk Factors; D013030:Spain
chemical_list: D006680:HLA Antigens; D006683:HLA-DQ Antigens; D059866:HLA-DQ beta-Chains; C069051:HLA-DQB1 antigen; D006684:HLA-DR Antigens; D059811:HLA-DRB1 Chains