rs7530511 — IL23R Leu310Pro

Missense variant in the IL-23 receptor that substitutes leucine for proline at position 310; the rare leucine allele (T) is associated with susceptibility to Graves' disease and rheumatoid arthritis through altered IL-23/Th17 immune signaling

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IL23R Leu310Pro — The Rare Leucine Allele in Thyroid and Joint Autoimmunity

The interleukin-23 receptor (IL-23R11 IL-23R
A transmembrane receptor subunit that pairs with IL-12Rβ1 to form the functional IL-23 receptor complex on Th17 cells, NK cells, and innate lymphoid cells) sits at a pivotal junction in the immune system: it receives signals from IL-23, a cytokine produced by dendritic cells and macrophages, and translates them into activation of Th17 cells22 Th17 cells
A subset of CD4+ helper T cells characterized by IL-17 production; central to mucosal immunity and implicated in many autoimmune diseases. rs7530511 introduces a missense change at codon 310 of IL-23R: the common C allele encodes Proline (Pro310), while the rare T allele encodes Leucine (Leu310). Globally, about 87% of people carry the C allele (Pro310) and only 13% carry the T allele, making the Leu310 form the minor variant. The TT homozygous (Leu/Leu) genotype is found in fewer than 2% of people of European descent and is extremely rare in East Asian populations (~0.02%).

The Mechanism

Position 310 of IL-23R falls within the fibronectin type III extracellular domain, a region involved in cytokine binding and receptor dimerization. Leucine and proline differ substantially in structure33 Leucine and proline differ substantially in structure
Proline's cyclic pyrrolidine ring creates a rigid kink in the polypeptide chain, whereas leucine is a flexible branched-chain residue — substituting leucine for proline at a structurally constrained position can alter local protein conformation. Proline is the population-common form (encoded by C allele, the major allele in all continental populations); the Leucine form (T allele) appears to confer modestly altered receptor function or stability. Computational predictions rate the C allele (Pro) as tolerated by SIFT and benign by PolyPhen, consistent with it being the evolutionarily maintained common form in humans. The T allele (Leu) has a SIFT score of 1 (tolerated) for the missense change at this position, suggesting a subtle rather than dramatic functional perturbation.

The mechanistic consequence may lie in altered IL-23 binding affinity or downstream JAK2/TYK244 JAK2/TYK2
Janus kinase family members that associate with the cytoplasmic tails of IL-23R and IL-12Rβ1; activated upon IL-23 binding to phosphorylate STAT3 and STAT4 signaling. Carriers of the T (Leu) allele may experience a subtly different IL-23 signaling set-point, shifting Th17 cell activation thresholds and contributing to an autoimmune-prone immune environment in certain tissues — including the thyroid gland.

The Evidence

The most striking finding comes from Huber et al. 200855 Huber et al. 2008
216 Graves' disease patients and 368 controls in a North American Caucasian cohort; studied four IL23R variants for association with Graves' disease and Graves' ophthalmopathy, which found that the TT genotype (Leu/Leu) was significantly associated with Graves' disease overall (2.5% in GD patients vs. 0.3% in controls, OR = 9.4, p = 0.02). Unlike the other IL23R variants in that study (rs2201841 and rs10889677), rs7530511 did not specifically track with Graves' ophthalmopathy but with GD broadly — suggesting the Leu310 form shifts susceptibility to thyroid autoimmunity through a mechanism distinct from eye-tissue-specific inflammation.

In rheumatoid arthritis, Dogru et al. 202266 Dogru et al. 2022
Turkish cohort from the South Aegean region studying IL-23R polymorphisms in RA found the CT genotype significantly more common in RA patients than controls. When combined with the AA genotype of the nearby rs1004819, the combination reached OR 4.9 (p = 0.0001), underscoring how IL23R haplotype context amplifies risk.

The variant also appears in ulcerative colitis data: Lv et al. 201277 Lv et al. 2012
Chinese Han population cohort for ulcerative colitis found the variant allele more frequent in UC cases (3.3%) than controls (0.7%, p = 0.002), though the study population and small absolute difference suggest caution in generalization.

An important observation concerns the direction reversal across traits. A meta-analysis of 13 studies on IL23R and psoriasis88 meta-analysis of 13 studies on IL23R and psoriasis
Capon et al. 2012, Inflamm Res found the T allele was protective against psoriasis (OR = 0.820, 95% CI 0.764–0.879, p = 0.001), the opposite direction from Graves' disease. This context-dependence — risk for one autoimmune condition, protection against another — is consistent with IL-23R's role as a central hub whose signaling calibration affects different disease-specific Th17 programs differentially.

Crucially, the association with Graves' disease does not replicate in East Asian populations: Ban et al. 200999 Ban et al. 2009
464 Japanese AITD patients and 179 controls with four IL23R SNPs studied found rs7530511 was not associated with GD, Graves' ophthalmopathy, or Hashimoto's thyroiditis in the Japanese cohort. The authors attributed this to ethnic specificity — and indeed, the T allele is very rare (~1.3%) in East Asian populations, making statistical power limited there. The Graves' disease signal is most relevant for individuals of European ancestry.

Overall evidence level is moderate: the Graves' disease finding is striking (OR 9.4) but based on a single moderate-sized Caucasian cohort; the RA and UC associations require replication; the direction reversal for psoriasis adds complexity. No clinical guidelines currently include this variant.

Practical Actions

For TT homozygotes of European ancestry, the Graves' disease association warrants proactive thyroid monitoring. Since Graves' disease is caused by stimulatory TSH-receptor antibodies driving thyroid overactivity, the key is early detection through TSH testing and TRAb (thyrotropin receptor antibody) measurement. Catching the disease before overt hyperthyroidism develops allows for less intensive treatment and better outcomes. CT heterozygotes carry an intermediate signal that warrants awareness but not aggressive screening absent symptoms.

Note that there is no supplement, diet, or lifestyle intervention known to counteract IL-23R-driven thyroid autoimmunity specifically. Selenium supplementation has independent evidence in autoimmune thyroiditis generally, but its benefit in rs7530511-specific Graves' disease susceptibility has not been studied.

Interactions

rs7530511 is one of several IL23R variants in the GeneOps database, each with distinct associations. rs11209026 (R381Q) is the most protective IL23R variant, strongly reducing IBD risk. rs2201841 (intronic) is associated with psoriasis and Crohn's susceptibility. rs1004819 appears to synergize with rs7530511 in rheumatoid arthritis (combined OR ≈ 4.9 when both risk genotypes are present). Individuals carrying risk genotypes at multiple IL23R loci may have a more broadly dysregulated IL-23/Th17 axis than any single variant predicts.

Beyond IL23R itself, interactions with other autoimmune loci — PTPN22 rs2476601 (R620W, a master autoimmunity risk variant affecting T-cell activation thresholds) and HLA-DR variants strongly associated with Graves' disease — are biologically expected but have not been quantified in combination with rs7530511 specifically.

Genotype Interpretations

What each possible genotype means for this variant.

CC Common Proline Form Normal

Common Pro310 genotype — typical IL-23 receptor function

You carry two copies of the C allele (Proline at position 310), the predominant form of IL-23R found in about 76% of people globally. The Proline form at this position is the evolutionarily maintained common variant across human populations. Your IL-23R function at this position is at or below population-average autoimmune risk; no elevated risk for Graves' disease from this variant has been identified for CC homozygotes.

CT Leu/Pro Heterozygote Intermediate

One leucine allele — modestly elevated IL-23R autoimmune signal

The CT heterozygote carries one Pro310 allele (C) and one Leu310 allele (T). The biological effect at the heterozygous level is incompletely characterized — the single case-control study in Graves' disease (Huber et al. 2008) focused on the TT genotype for its strong OR 9.4 finding, and heterozygous data were not broken out with sufficient power. The rheumatoid arthritis finding (Dogru et al. 2022) showed CT as the genotype elevated in cases. Evidence level remains moderate given the limited number of replication studies.

TT Rare Leu/Leu Homozygote High Risk

Homozygous rare leucine allele — elevated Graves' disease susceptibility

Graves' disease is the most common cause of hyperthyroidism, driven by thyrotropin receptor antibodies (TRAb) that mimic TSH and constitutively activate thyroid hormone production. The IL-23/Th17 axis — in which IL-23R is a key mediator — plays a documented role in thyroid autoimmunity. IL-17-producing Th17 cells have been found infiltrating thyroid tissue in Graves' disease, and elevated IL-17 serum levels are reported in active GD patients. How Leu310 (TT genotype) specifically alters IL-23R signaling to promote thyroid Th17 infiltration is not fully established mechanistically, but the association data from the Huber 2008 study is notable for its effect size.

The TT genotype also places this individual at an intersection of IL23R haplotype risk. Rheumatoid arthritis studies (Dogru et al. 2022) show that IL23R rs7530511 risk genotypes compound with adjacent rs1004819 genotypes. Combined, these haplotype configurations reached OR 4.9 for RA susceptibility, suggesting the broader IL23R locus is a genuine autoimmune risk hub for multiple conditions beyond thyroid disease.

It is important to note that the T allele is protective against psoriasis in European populations (meta-analysis OR 0.82). This directional heterogeneity — the same allele raising risk for one autoimmune disease while protecting from another — reflects the complex role of IL-23/Th17 biology, where tissue-specific Th17 programs drive distinct disease manifestations.