ON THE HLA-DQ(ALPHA-1-ASTERISK-0501, BETA-1-ASTERISK-0201)-ASSOCIATEDSUSCEPTIBILITY IN CELIAC-DISEASE - A POSSIBLE GENE DOSAGE EFFECT OF DQB1-ASTERISK-0201

The HLA-associated susceptibility to develop celiac disease (CD) seems mainly to be conferred by a particular HLA-DQ heterodimer encoded by the DQA10501 and DQB1*0201 genes either in cis or in trans position. To study the possible influence of DRB1 or other DQA1 and DQB1 alleles on the CD susceptibility conferred by these DQ genes, we performed ge nomic HLA typing of 94 CD patients, selected those who carried at leas t one copy of the DRB10301-DQA1*0501-DQB1*0201 haplotype (N = 89) and compared them to 47 random, healthy Norwegians matched with the patie nts to carry at least one copy of the above haplotype. We found an exc ess of DQB10201 homozygosity in the patients. This was due to an incr eased frequency of the DRB10301-DQA1*0501-DQB1*0201 and DRB1*0701-DQA 10201-DQB1*0201 haplotypes present on the other chromosome. We propos e that, in individuals carrying the DQA10501 and DQB1*0201 alleles, t he presence of a second copy of the DQB10201 allele increases suscept ibility to CD.