Does the HLA-DQA1 rs2187668 risk allele increase susceptibility to gliadin immune reactivity?

An individual's genetic profile can reveal a strong predisposition to gluten-related autoimmunity, but translating this genetic risk into active mucosal expression requires validated clinical markers.

Genetic susceptibility and molecular mechanisms

• HLA-DQ2.5 tagging: The HLA-DQA1 rs2187668 polymorphism is a highly robust genetic tag for the HLA-DQ2.5 haplotype (DQA1*05:01/DQB1*02:01).
• T-cell presentation: This haplotype encodes the major histocompatibility complex (MHC) class II heterodimeric receptor. This receptor directly binds and presents deamidated gliadin (gluten) peptides to CD4+ T cells, serving as the foundational molecular pathway driving gluten-induced immune reactivity.
• Risk quantification: Genome-wide association studies show that the risk-associated allele carries an odds ratio of approximately 6.0 to 8.0 for celiac disease. Homozygosity (A/A or T/T) represents the highest risk configuration. However, genetic carriage is susceptibility-based rather than deterministic, as only about 3% of HLA-DQ2.5 carriers go on to develop clinical celiac disease.

Mucosal expression and stool IgA limitations

• Lack of clinical validation: Major medical guidelines from the American College of Gastroenterology (ACG) and the European Society for Paediatric Gastroenterology, Hepatology and Nutrition (ESPGHAN) do not recommend fecal anti-gliadin IgA assays, designating them as unvalidated and non-standard.
• Poor diagnostic accuracy: Research indicates that fecal secretory IgA anti-gliadin antibodies suffer from extremely low diagnostic sensitivity, missing approximately 94% of biopsy-proven cases in validation studies.
• No link to genetic expression: There is no scientific or mechanistic evidence linking fecal anti-gliadin IgA levels to HLA genetic susceptibility, and it is not validated as an index of active mucosal-level genetic expression.

Bottom line

• While the HLA-DQA1 rs2187668 allele is a validated genetic marker that significantly increases susceptibility to gliadin reactivity, an elevated stool anti-gliadin IgA test is clinically unvalidated and does not indicate that this genetic susceptibility is actively expressing at the gut mucosal level. Standard serology and duodenal biopsy remain the only validated diagnostic pathways.