Abstract
Introduction: Human leukocyte antigen (HLA) locus is the major genetic risk factor for autoimmune endocrine diseases. The amino acid variability at the HLA-DQβ1 position 57 encoded by both DQB1 alleles was identified as critical risk residue for type 1 diabetes. We therefore investigated this amino acid residue at HLA-DQβ1 position 57 in Graves’ disease (GD). Subjects and methods: DNA samples were obtained from 572 healthy controls (HC, 262 females/310 males) and 299 patients with GD (255 females/44 males) and genotyped for HLA-DQB1 using a sequence specific primer (SSP, 13 primer pairs) approach. The PCR amplified products were analyzed by gel electrophoresis. The HLA-DQB1 alleles were defined with their corresponding amino acid residues at the DQß chain positon 57 as follows: Ala(57) (DQB1*0201,*0302), Asp(57) (DQB1*0301,*0303,*0401,*0402,*0503,*0601,*0602*,0603) Val(57) (DQB1*0501,*0604) and Ser(57) (DQB1*0502). Finally, the frequencies for amino acid variabilities and their combinations (Ala/Ala, Ala/non-Ala and non-Ala/non-Ala) were calculated and compared by Pearson-Mantel-Haenszel Chi-squared test. Results: The presence of Ala(57) was significantly more frequent in patients with GD compared to HC (25% vs. 39%, OR: 1.77; p=7x10(-4)), whereas Val(57) was less frequent (19% vs. 12%, OR: 0.59; p=0.04). In contrast, no difference in the distribution between GD and HC concerning the amino acids Asp(57) and Ser(57) was observable. Similar results were found in female (Ala(57) 23% vs. 38%, OR:2.01; p=1.2x10(-3) and Val(57) 19% vs. 13%, OR:0.35; p=1.2x10(-4)) but not in males (p >0.5). Furthermore, homozygous HLA-DQB1 Ala (8% vs. 15%, OR:1.98; p=5x10(-3)) as well as heterozygous HLA-DQB1 Ala/non-Ala (34% vs. 45%, OR:1.58; pc=5x10(-3)) were significantly more prevalent, while non-Ala/non-Ala (58% vs. 40%, OR:0.49 pc=3x5x10(-6)) was found to be less frequent in patients than in HC. By gender stratification there was a significant difference between female patients with GD and female HC in the distribution of the mentioned amino acid combinations (Ala p=4.5x10(-3), Ala/non-Ala pc=0.02, non-Ala/non-Ala p=1x10(-5)). Conclusion: We identify a strongly predisposing role for HLA-DQβ1 Ala(5 7)to GD, particularly in women, highlighting the gender specific disease risk. Immunogenetic testing may pave the way towards personalized treatment.