JCEM-jc-2019-01933-FROMMER-SUPPLEMENTAL_MATERIAL

Context: The structure of the human leucocyte antigen (HLA) peptide-binding clefts strongly contributes to monoglandular and polyglandular autoimmunity (AP). Objective: To investigate the impact of amino acid polymorphisms on the peptide binding interactions within HLA class II and its association with AP Design: immunogenetic study Setting: Tertiary referral center for autoimmune endocrine diseases Subjects: 587 subjects with AP, autoimmune thyroid disease (AITD), type 1 diabetes (T1D) and healthy unrelated controls were typed for HLA class II. Methods: Amino acids within the peptide binding cleft that are encoded by HLA class II exon 2 were listed for all codon positions in all subjects. Overall comparisons between disease and control groups with respect to allele distribution at a given locus were performed by assembling rare alleles applying an exact Freeman Halton contingency table test with Monte-Carlo p values based on 150,000 samples. Results: The Montecarlo Exact Fisher Test demonstrated marked differences in all three Loci, DQA1, DQB1, DRB1 (p<0.0001) between AP versus both AITD and controls, as well as between AP type II (Addison’s disease as major endocrine component) and AP type III (T1D + AITD). Differences were also noted between AP and T1D pertaining to the DRB1 allele (p<0.041). The following seven amino acid positions DRB1-13, DRB1-26, DRB1-71, DRB1-74, DQA1-47, DQA1-56, and DQB1-57 significantly contributed to AP. Five positions in DQA1 (11, 47, 50, 56, and 69) completely correlated (p<0.0001). Conclusion: Amino acid polymorphisms within HLA class II exon 2 mediate the AP risk and differentiate between thyroid and polyglandular autoimmunity.