Do CD40, CTLA4, and HLA-DQA1 variants increase autoimmune thyroid disease susceptibility?

Genetic variations in CD40, CTLA4, and HLA-DQA1 alter key immune pathways, directly influencing susceptibility to autoimmune thyroid diseases (AITD) such as Graves' disease and Hashimoto's thyroiditis.

Clinical evidence and susceptibility

• CD40 polymorphisms: Carrying the CD40 rs1883832 C risk allele (especially the CC genotype) is associated with a 1.2- to 1.9-fold increased susceptibility to Graves' disease. However, this variant shows no significant association with Hashimoto's thyroiditis.
• CTLA4 polymorphisms: The CTLA4 rs231775 G allele (specifically the GG genotype) is a recognized risk factor for both Graves' disease and Hashimoto's thyroiditis, conveying an odds ratio of approximately 1.3 to 1.6.
• HLA-DQA1 haplotypes: Specific alleles, such as DQA10501* and DQA10301*, convey some of the strongest genetic risks for developing AITD, though these effects are highly population-specific.

Mechanistic pathways

• Altered costimulation: The functional CD40 rs1883832 (-1C>T) variant alters a Kozak sequence, which increases CD40 costimulatory molecule expression and subsequently enhances B- and T-cell activation.
• Impaired negative regulation: The CTLA4 rs231775 (+49A>G) variant causes a Thr17Ala amino acid substitution in the signal peptide. This reduces glycosylation efficiency and decreases CTLA-4 cell-surface expression, weakening the critical inhibitory signals required to downregulate T cells.
• Aberrant antigen presentation: Variants in HLA-DQA1 disrupt self-tolerance by altering how self-thyroid antigens are presented to and recognized by CD4+ T cells, triggering autoimmune targeting of the thyroid.

Bottom line

• Polymorphisms in CD40, CTLA4, and HLA-DQA1 drive susceptibility to autoimmune thyroid diseases by altering costimulatory signaling, impairing T-cell negative regulation, and disrupting self-antigen presentation.