JCEM-jc-2019-01933-FROMMER-SUPPLEMENTAL_MATERIAL

<br><b>Context</b>: The structure of the human leucocyte antigen (HLA) peptide-binding clefts strongly contributes to monoglandular and polyglandular autoimmunity (AP). <br><b>Objective</b>: To investigate the impact of amino acid polymorphisms on the peptide binding interactions within HLA class II and its association with AP <br><b>Design: </b>immunogenetic study <br><b>Setting</b>: Tertiary referral center for autoimmune endocrine diseases <br><b>Subjects</b>: 587 subjects with AP, autoimmune thyroid disease (AITD), type 1 diabetes (T1D) and healthy unrelated controls were typed for HLA class II. <br><b>Methods: </b>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. <br><b>Results</b>: The Montecarlo Exact Fisher Test demonstrated marked differences in all three Loci, <i>DQA1</i>, <i>DQB1</i>, <i>DRB1</i> (p&lt;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 <i>DRB1</i> allele (p&lt;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 <i>DQA1</i> (11, 47, 50, 56, and 69) completely correlated (p&lt;0.0001). <br><b>Conclusion</b>: Amino acid polymorphisms within HLA class II exon 2 mediate the AP risk and differentiate between thyroid and polyglandular autoimmunity. <br>