rs3816769 — STAT3 STAT3 co-variant

Intronic STAT3 variant where the T allele (reference, ~66%) increases risk for autoimmune thyroid disease, Crohn's disease, and lung cancer while the protective C allele correlates with higher STAT3 expression

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STAT3's Dual Face: When the Common Allele Raises Risk

STAT311 STAT3
Signal Transducer and Activator of Transcription 3 — a transcription factor that converts cytokine receptor signals (IL-6, IL-10, IL-21, IL-23, and many others) into gene expression changes occupies one of the most contested positions in immunology: it is simultaneously required for anti-inflammatory resolution and for driving the Th17 cell differentiation that underlies autoimmune pathology. This intronic variant at position 42,346,255 on chromosome 17 sits inside STAT3 and has been independently associated with autoimmune thyroid disease, inflammatory bowel disease, psoriasis, and lung cancer across populations spanning New Zealand, Poland, and Turkey. Unusually, the T allele — the majority allele, carried by roughly two thirds of the global population — is the risk variant, while the minority C allele is protective.

The Mechanism

rs3816769 is an intronic variant that does not alter the STAT3 protein sequence directly. The preliminary gene expression data from Domańska et al. (2013) suggest the TT genotype correlates with higher STAT3 transcript levels in non-small cell lung cancer tissue (p=0.0464), which fits the broader biology: elevated STAT3 expression is a double-edged sword. Acute, transient STAT3 activation resolves inflammation by driving IL-10-producing regulatory cells and suppressing NF-κB. But chronic, constitutive STAT3 signaling — the kind that elevated baseline expression could produce — promotes Th17 differentiation, amplifies IL-17 and IL-21 production, sustains autoantibody-promoting follicular helper T cell programs, and drives tumour immune evasion. The rs3816769 intronic position may overlap an enhancer or splicing regulatory element22 enhancer or splicing regulatory element
Intronic regulatory sequences that control transcript isoform ratios or expression magnitude in immune cells that modulates how strongly STAT3 responds to cytokine stimulation. The variant is in strong linkage disequilibrium with rs744166 (another STAT3 intronic variant) and rs1053004, suggesting these SNPs travel together as a haplotype block and may collectively determine STAT3 regulatory output.

The Evidence

The most statistically robust finding comes from Ferguson et al.33 Ferguson et al.
"Genetic factors in chronic inflammation: single nucleotide polymorphisms in the STAT-JAK pathway, susceptibility to DNA damage and Crohn's disease in a New Zealand population," Mutation Research 2010, a case-control study of 302 Crohn's disease patients and 382 controls. The C allele was significantly less frequent in CD patients than in controls (OR=0.71, 95% CI 0.56–0.89, p=0.003), confirming the C allele is protective. Notably, T-allele carriers showed significantly enhanced susceptibility to DNA damage in peripheral blood leukocytes (comet assay), a finding suggesting the variant affects not just immune signalling but genomic stability under inflammatory stress. T-allele carriers also had higher rates of colonic disease location and extra-intestinal manifestations.

In autoimmune thyroid disease, Kotkowska et al.44 Kotkowska et al.
"Single nucleotide polymorphisms in the STAT3 gene influence AITD susceptibility, thyroid autoantibody levels, and IL6 and IL17 secretion," Cell Mol Biol Lett 2015 studied 71 AITD patients (39 Hashimoto's thyroiditis, 32 Graves' disease) and 40 controls, finding the C allele and CC genotype significantly over-represented in healthy controls. The CT genotype in Hashimoto's patients was associated with elevated thyroglobulin antibody (TgAb) titres — a direct measure of thyroid autoimmunity severity. The authors also observed that STAT3 genotype influenced ex vivo IL-6 and IL-17 secretion from peripheral blood cells, providing mechanistic support for the epidemiological associations.

In inflammatory bowel disease, Can et al.55 Can et al.
"Investigation of IL23R, JAK2, and STAT3 gene polymorphisms in Crohn's disease and ulcerative colitis in a Turkish population," Turkish Journal of Gastroenterology 2016 found rs3816769 associated with Crohn's disease subphenotype and with requirement for immunosuppression in ulcerative colitis — suggesting the variant predicts disease severity beyond initial susceptibility.

A preliminary lung cancer study66 preliminary lung cancer study
Domańska et al. 2013, 71 NSCLC patients vs 104 controls — treat as hypothesis-generating until replicated reported TT genotype association with both elevated NSCLC risk and higher tumour STAT3 expression. STAT3 is a well-validated oncogene and the expression correlation (p=0.0464) is biologically plausible, though the small sample warrants independent replication.

Practical Actions

For carriers of one or two T alleles, the actionable insight is about immune surveillance and inflammation monitoring rather than any single drug. Chronically elevated STAT3 signalling promotes Th17-mediated autoimmunity, so the priority is keeping the upstream cytokine environment that activates STAT3 — particularly IL-6, IL-17, and IL-23 — from running unchecked. Long-chain omega-3 fatty acids (EPA+DHA) suppress IL-6 and IL-17 production; adequate vitamin D maintains the T-regulatory/Th17 balance that STAT3 signalling mediates. For TT carriers with established autoimmune thyroid disease or IBD, JAK inhibitors (which block STAT3 phosphorylation) represent mechanistically matched systemic therapy options when standard first-line therapies are insufficient.

Interactions

rs3816769 is in strong LD with rs74416677 rs744166
STAT3 intronic variant — associated with IBD, atopic dermatitis, and multiple autoimmune phenotypes across large GWAS studies and rs105300488 rs1053004
STAT3 intronic variant, part of the same haplotype block (r²=0.704 with rs3816769), and is co-listed in research with rs1788132099 rs17881320
STAT3 intronic variant associated with atopic dermatitis (OR=1.09 in meta-analysis of 862,032 individuals). Together these STAT3 intronic variants likely form a regulatory haplotype that collectively sets STAT3 expression level and cytokine responsiveness in immune cells. The combined haplotype burden across the STAT3 locus may predict autoimmune risk more powerfully than any single variant.

Genotype Interpretations

What each possible genotype means for this variant.

CC Protective STAT3 Variant Beneficial

Protective genotype — C allele homozygosity reduces autoimmune and IBD risk

You carry two copies of the minor C allele at this STAT3 intronic position. Studies across Crohn's disease (OR=0.71 for C allele, p=0.003), autoimmune thyroid disease, and lung cancer consistently find the CC genotype in controls at higher rates than in patients. About 12% of people globally carry this genotype. Your STAT3 regulatory variant appears to be calibrated toward lower chronic inflammation through this locus.

CT Intermediate STAT3 Risk Intermediate

One copy of the T risk allele; moderately elevated autoimmune and IBD susceptibility

The TC genotype places you between the protective CC and the higher-risk TT. In the Kotkowska et al. study (PMID 26204395), CT genotype Hashimoto's patients had significantly elevated thyroglobulin antibody titres compared to controls, indicating that even one T allele can measurably amplify thyroid autoantibody production. The Ferguson et al. study (PMID 20109474) showed an additive allele effect in Crohn's disease, with each T allele shifting inflammatory disease location and extra-intestinal manifestation risk.

The Kotkowska study also showed that STAT3 genotype influences ex vivo IL-6 and IL-17 secretion — cytokines central to both Th17-driven autoimmunity and gut mucosal inflammation. This biological signal suggests the variant acts early in the inflammatory cascade rather than downstream in tissue damage.

TT Elevated STAT3 Risk High Risk

Homozygous T allele — highest susceptibility to STAT3-driven autoimmune and inflammatory disease from this variant

The TT genotype at rs3816769 represents homozygosity for the risk allele identified consistently across multiple independent studies. In the strongest study (Ferguson et al., PMID 20109474), the C allele showed a protective OR of 0.71 in Crohn's disease (p=0.003) — meaning TT carries the inverse elevated risk compared to CC. The same study found T allele carriers have measurably higher DNA damage susceptibility in peripheral blood leukocytes (comet assay), suggesting chronic inflammatory oxidative stress compounds with this genotype.

In autoimmune thyroid disease (Kotkowska et al., PMID 26204395), the CC genotype was concentrated in controls, with TT over-represented in Hashimoto's and Graves' patients. The CT genotype already showed elevated TgAb in HT patients; TT is expected to amplify this further given the additive model. The same study showed STAT3 genotype influences IL-6 and IL-17 secretion ex vivo — the upstream cytokines that drive both Th17 polarisation and thyroid autoimmunity.

In the preliminary lung cancer data (Domańska et al., PMID 24382554, n=71 patients), TT genotype correlated with STAT3 overexpression in NSCLC tumour tissue (p=0.0464). STAT3 is a validated oncogenic transcription factor that promotes tumour immune evasion and cell survival; the expression-genotype link, while requiring replication, is biologically consistent with the intronic variant's regulatory role.

For IBD, Can et al. (PMID 27852544) found rs3816769 associated not only with Crohn's disease subphenotype but with the need for immunosuppression in ulcerative colitis — a proxy for more aggressive disease course.