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.