Does HLA-DQA1 rs2187668 CT increase gluten-related immune reactivity?

The intestinal barrier and mucosal immune response are regulated by a complex interplay between genetic predisposition and nutritional factors.

Genetic susceptibility

• The HLA-DQA1 rs2187668 CT (heterozygous) genotype serves as a genetic tag for the HLA-DQ2.5 haplotype, the primary genetic driver of gluten-related celiac disease.
• Carrying this heterozygous variant modulates genetic predisposition, conferring a 2- to 2.3-fold increase in susceptibility to gluten-related immune reactivity compared to non-carriers.
• Although highly prevalent in the general population—with only about 3% of carriers developing clinical celiac disease—its absence has a high negative predictive value, effectively ruling out celiac susceptibility.

Mechanistic barrier degradation

• Vitamin D signaling: Active vitamin D, acting through the vitamin D receptor (VDR), transcriptionally regulates key tight junction proteins, including zonula occludens-1 (ZO-1), occludin, and claudins. Deficiency impairs this transcriptional upregulation, weakening tight junctions and compromising regulatory T cell (Treg) development, which skews mucosal immunity toward pro-inflammatory Th1 and Th17 responses.
• Zinc homeostasis: Zinc is a crucial cofactor for epithelial repair and tight junction stability. Zinc depletion triggers the proteolysis of occludin, downregulates claudin-3 transcription, and causes the mislocalization of ZO-1.
• Combined impact: This dual micronutrient deprivation compromises physical cell-to-cell connections and increases paracellular permeability, allowing unregulated antigen translocation that further destabilizes mucosal tolerance.

Bottom line

• The HLA-DQA1 rs2187668 CT genotype doubles genetic susceptibility to gluten-related reactivity by tagging the HLA-DQ2.5 haplotype, while concurrent deficiencies in vitamin D and zinc synergistically weaken the physical gut barrier (via ZO-1, occludin, and claudin disruption) and compromise active mucosal immune tolerance.