Is HLA-DQA1 rs2187668 linked to celiac disease risk and gliadin-directed immune responses?

The HLA-DQA1 rs2187668 polymorphism is a critical genetic marker for celiac disease susceptibility, serving as a high-fidelity surrogate for the HLA-DQ2.5 haplotype.

Genetic linkage and diagnostic utility

• High-fidelity surrogate: The intronic single nucleotide polymorphism (SNP) rs2187668 is in exceptionally tight linkage disequilibrium with the celiac-predisposing HLA-DQ2.5 haplotype (consisting of the cis-encoded alleles DQA105:01 and DQB102:01), exhibiting r² values ranging from 0.97 to 0.99 in European-derived and Saudi populations.
• Clinical screening efficiency: Because the HLA-DQ2.5 haplotype is present in 90% to 95% of individuals diagnosed with celiac disease, genotyping the rs2187668 risk allele serves as a highly sensitive and cost-effective screening tool to stratify disease risk.

Molecular mechanisms of pathogenesis

• Heterodimer assembly: The HLA-DQ2.5 haplotype directly encodes the alpha and beta chains that form the functional HLA-DQ2.5 MHC class II heterodimeric protein.
• Antigen-binding specificity: The antigen-binding groove of the HLA-DQ2.5 heterodimer is structurally and electrostatically optimized to bind negatively charged, deamidated gliadin peptides, which are chemically modified in the gut by tissue transglutaminase.
• Immune cascade initiation: Presentation of these deamidated gliadin-DQ2.5 complexes to gut-localized CD4+ T helper cells triggers a pro-inflammatory cascade, driving B-cell activation and autoimmune enteropathy. Carrying this genetic signature increases the risk of developing celiac disease up to sevenfold, while its absence virtually rules out classic gluten-driven autoimmunity.

Bottom line

• HLA-DQA1 rs2187668 is a highly validated genetic proxy for the HLA-DQ2.5 haplotype, which directly drives celiac disease susceptibility by expressing a specialized heterodimer optimized to present immunogenic deamidated gliadin peptides to CD4+ T cells.