Are CTLA4 rs3087243 GG and rs231775 GG linked to autoimmune thyroid disease and elevated TPO antibodies?

Cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) serves as a critical immune checkpoint that maintains peripheral tolerance by downregulating T-cell activation. Functional polymorphisms within the CTLA4 gene directly undermine this protective pathway, predisposing individuals to autoimmune thyroid diseases (AITD).

Mechanistic breakdown of immune tolerance

• Impaired checkpoint signaling: The CTLA4 rs3087243 (CT60) GG genotype impairs splicing efficiency, leading to decreased levels of soluble CTLA-4 (sCTLA-4) and reduced receptor expression on Foxp3⁺ CD25⁺ regulatory T cells (Tregs).
• Defective cellular trafficking: The rs231775 (+49A/G) GG genotype alters signal peptide processing, which reduces surface expression and trafficking of membrane-bound CTLA-4.
• T-cell hyperactivation: Together, these deficits limit the competitive inhibition of CD80/CD86, allowing unchecked co-stimulation, T-cell hyperactivation, and a breakdown of peripheral self-tolerance.

Susceptibility and thyroid autoantibody expression

• Increased AITD risk: Genetic meta-analyses confirm that the rs231775 GG genotype significantly increases susceptibility to Graves’ disease (OR ~2.0 to 2.75) and Hashimoto’s thyroiditis (OR ~2.10). Similarly, the rs3087243 GG genotype carries an approximate 1.6- to 2.0-fold increased risk of thyroid autoimmunity.
• Elevated TPO antibodies: These risk genotypes function as quantitative trait loci that directly correlate with elevated thyroid peroxidase (TPO) antibody titers. Compromised T-cell regulation allows the expansion of autoreactive B cells, making elevated TPO antibodies a direct serological marker of the underlying genetically driven loss of tolerance.

Bottom line

The CTLA4 rs3087243 GG and rs231775 GG genotypes represent established risk factors that compromise T-cell checkpoint regulation and directly drive susceptibility to autoimmune thyroid disease, manifesting clinically as elevated TPO antibody levels.