rs2234663 — IL1RN

Intron 2 VNTR polymorphism in IL1RN that alters IL-1Ra isoform balance and is associated with increased susceptibility to gastric cancer after H. pylori infection, severe chronic periodontitis, SLE, COPD, and post-traumatic osteomyelitis through dysregulated IL-1/IL-1Ra signaling

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IL1RN Intron 2 VNTR — When the Brake on Inflammation Is Wired Differently

The immune system's inflammatory response is governed not just by the molecules that ignite inflammation, but equally by those that extinguish it. Interleukin-1 receptor antagonist (IL-1Ra)11 Interleukin-1 receptor antagonist (IL-1Ra)
The natural protein inhibitor of IL-1α and IL-1β — it occupies the IL-1 receptor without triggering signaling, acting as a competitive brake on the entire IL-1 cytokine axis is one of the most important of these brakes. Encoded by the IL1RN gene on chromosome 2q14.1, IL-1Ra is the direct target of anakinra, a recombinant form of the protein used clinically in rheumatoid arthritis and systemic autoinflammatory diseases. The rs2234663 polymorphism is a variable number tandem repeat (VNTR)22 variable number tandem repeat (VNTR)
A type of DNA polymorphism where a short DNA sequence is repeated a different number of times in different individuals; this particular VNTR consists of an 86 base-pair repeat unit in intron 2 of IL1RN, present in 2, 3, 4, 5, or 6 copies depending on the allele located in the second intron of IL1RN. The most clinically relevant distinction is between the A1 allele (4 copies of the 86bp repeat — the common form) and the A2 allele (2 copies — the shorter, risk-associated form). Together these two alleles account for over 95% of chromosomes studied.

The Mechanism

The intron 2 VNTR does not alter the IL-1Ra protein sequence, but it does alter how the gene is regulated. The repeated 86bp units contain binding sites for transcription factors and splicing regulators33 binding sites for transcription factors and splicing regulators
These include sites resembling SP1, TCF, and other regulatory elements; the number of repeat copies changes the chromatin architecture and accessibility of the intron 2 region, influencing alternative transcript initiation and splicing. IL1RN produces four distinct protein isoforms through alternative promoter usage and splicing: the secreted form (sIL-1Ra, the dominant circulating antagonist) and three intracellular forms (icIL-1Ra I, II, and III). The A2 allele alters the balance between these isoforms in ways that are cell-type and context-dependent. The net effect in inflammatory tissues — particularly mucosal surfaces such as gastric mucosa and periodontium — is an insufficient IL-1Ra response that allows IL-1β-driven inflammation to persist and amplify unchecked.

This is consistent with a broader principle in IL-1 biology: the critical parameter is not IL-1β concentration alone, but the IL-1β:IL-1Ra ratio44 IL-1β:IL-1Ra ratio
The relative amounts of the pro-inflammatory IL-1β and its endogenous antagonist IL-1Ra. When IL-1Ra production is insufficient relative to the IL-1β signal, even modest IL-1β levels can drive sustained tissue-destructive inflammation. The A2 allele shifts this ratio toward greater effective IL-1β activity at sites where it matters most.

The Evidence

The landmark connection between the IL1RN VNTR and gastric cancer was established by El-Omar et al. 200055 El-Omar et al. 2000
Nature 404:398-402; case-control and cohort studies showing IL-1 cluster polymorphisms associated with hypochlorhydria after H. pylori infection and gastric cancer development in Nature, demonstrating that individuals with certain IL-1 cluster variants who become infected with H. pylori develop more extensive corpus gastritis, progressing to hypochlorhydria and atrophy — the recognized precancer sequence. H. pylori activates IL-1β production in the gastric mucosa; the IL-1RN VNTR modulates how effectively IL-1Ra can contain this response. In a Brazilian study of 675 individuals, Oliveira et al. 201266 Oliveira et al. 2012
Mol Biol Rep 39:7617; 229 gastritis cases, 200 gastric cancer cases, 246 controls found the IL-1RN A2 allele associated with gastric cancer (OR=3.04, p<0.01) and chronic gastritis (OR=2.32, p=0.02) in a recessive model. An Omani study of 118 gastric cancer patients confirmed A2 association (OR=2.2, p=0.04), amplifying to OR=3.5 in H. pylori-positive individuals.

In the periodontium, Ding et al. 201277 Ding et al. 2012
Arch Oral Biol 57:585; meta-analysis of 19 studies, 2,011 chronic periodontitis cases and 1,719 controls found the VNTR polymorphism marginally associated with chronic periodontitis overall (OR=1.47, p=0.05), but strongly associated with severe disease (OR=4.02, 95% CI 1.84–8.80, p<0.0005). This dose-dependent severity effect is characteristic of a variant that shifts the threshold for inflammation resolution rather than simply turning on disease.

For systemic lupus erythematosus, a Bulgarian case-control study (55 SLE patients, 112 controls) found Kamenarska et al. 201488 Kamenarska et al. 2014
Dermatol Res Pract; OR=2.5, 95% CI 1.2–5.4 for A2 allele in SLE patients. For COPD, a systematic review and meta-analysis of 26 studies identified IL1RN rs2234663 as showing a strong association with COPD susceptibility among interleukin gene variants — consistent with the variant's role in modulating inflammatory persistence in chronically exposed airways. For bone infections, a study of 153 trauma patients found the A2/A2 genotype associated with sevenfold increased osteomyelitis risk (OR=7, p<0.001), particularly for Staphylococcus aureus infections — likely reflecting inadequate IL-1Ra-mediated control of IL-1β at the bone-infection interface.

The picture for rheumatoid arthritis is more complex. A meta-analysis of 15 case-control studies found no significant overall association (A2/A2 OR=0.96, p=0.77), though a Mexican case-control study of 657 participants found A1/A2 heterozygotes at modestly elevated RA risk (OR=1.45, p=0.03) with A2/A2 homozygotes showing higher disease activity. Population heterogeneity in LD structure may explain these inconsistencies.

Practical Actions

The actionable implications concentrate on two areas where the evidence is strongest: H. pylori-related gastric disease and periodontal inflammation. For A2 carriers, especially A2/A2 homozygotes, the IL-1β:IL-1Ra imbalance creates a tissue environment where inflammatory damage at mucosal surfaces is harder to resolve. Catching H. pylori infection early and treating it decisively is more important for A2 carriers than for the general population. In the mouth, the severely elevated periodontitis risk for A2 carriers (OR=4+ for severe disease) makes professional dental assessment essential — this is one of the largest genetic effect sizes documented for periodontitis susceptibility.

Interactions

The IL1RN VNTR does not act in isolation — it is part of the IL-1 gene cluster on chromosome 2q14.1 alongside IL-1α (IL1A) and IL-1β (IL1B). The functionally critical pairing is between IL1RN rs2234663 and IL-1B rs1143634 (+3954 C>T) or rs16944 (-511 C>T). When a carrier has both increased IL-1β production (IL1B risk alleles) AND reduced effective IL-1Ra response (IL1RN A2), the IL-1β:IL-1Ra ratio is shifted at both ends simultaneously. This synergy has been documented for gastric cancer, chronic periodontitis, and COPD — with combined genotype odds ratios substantially exceeding those of either variant alone. These combinations represent strong candidates for compound actions in carriers who have been typed at both loci.

Genotype Interpretations

What each possible genotype means for this variant.

II Standard IL-1Ra Activity Normal

Common homozygous genotype; standard IL-1Ra isoform balance

You carry two copies of the A1 allele (four 86bp repeats) at the IL1RN intron 2 VNTR. This is the most common genotype globally, found in approximately 48% of people. Your IL1RN gene produces IL-1Ra isoforms in the standard proportions, supporting normal modulation of IL-1β activity at mucosal surfaces and in systemic inflammatory responses. Your risk for IL1RN-variant-driven gastric, periodontal, and inflammatory conditions is at population average for this locus.

DI Heterozygous A2 Carrier Intermediate

One shorter A2 allele; moderately altered IL-1/IL-1Ra balance

As an A1/A2 heterozygote, you produce IL-1Ra from one standard-activity allele and one A2-variant allele. The net effect on IL-1Ra isoform balance depends on tissue context and co-inflammatory signals. In the gastric mucosa during H. pylori infection, this partial reduction in effective IL-1Ra may be sufficient to allow more persistent IL-1β-driven atrophic gastritis in some individuals. In periodontal tissue, chronic bacterial challenge activates IL-1β production in the gingival crevice; heterozygous A2 carriers show modestly impaired resolution of this response compared to A1/A1 carriers. A Mexican study of 657 participants found A1/A2 genotype associated with RA susceptibility (OR=1.45, p=0.03), though a meta-analysis of 15 studies found no overall RA association, pointing to population heterogeneity. The most actionable implication at this genotype is enhanced oral hygiene and H. pylori awareness.

DD Homozygous A2 Carrier High Risk

Two copies of the shorter A2 allele; significantly altered IL-1/IL-1Ra balance

Homozygous A2/A2 individuals have no A1 (four-repeat) allele to contribute standard IL-1Ra activity. The resulting shift in IL-1β:IL-1Ra ratio is most consequential at sites of chronic antigenic challenge: gastric mucosa with H. pylori, the periodontal sulcus with periodontal pathogens, the airways in COPD, and at sites of post-traumatic infection. In the gastric cancer pathway, the sequence runs: H. pylori infection → IL-1β-driven corpus gastritis → hypochlorhydria → gastric atrophy → intestinal metaplasia → dysplasia → adenocarcinoma. The IL1RN A2/A2 genotype amplifies the inflammatory component of this pathway. The Oliveira 2012 study found OR=3.04 in a recessive model consistent with A2/A2 driving the effect.

For periodontal disease, the meta-analysis effect size for severe chronic periodontitis (OR=4.02) is one of the largest genetic effect sizes documented for any periodontitis susceptibility variant. A2/A2 individuals who receive standard once-yearly dental visits without periodontal monitoring are being significantly under-served.

For autoimmune conditions: while RA evidence is heterogeneous across populations, the SLE association (OR=2.5) and the documented role of IL-1Ra in suppressing neutrophil activation and inflammasome outputs suggest that any personal or family history of systemic autoimmune disease warrants proactive evaluation in A2/A2 carriers.