rs1295686 — IL13 IL-13 Atopy Promoter Variant

Intronic variant in IL13 that tags the atopic risk haplotype; the minor T allele co-segregates with rs20541 (R130Q) and rs1295685 on the same risk haplotype block and is consistently associated with elevated serum IgE, asthma susceptibility, atopic dermatitis, and food allergy through amplified IL-13 Th2 signaling

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IL-13 Atopy Haplotype Tag — Intronic Marker of the Th2 Cytokine Risk Block

Interleukin-1311 Interleukin-13
IL-13 is a Th2 cytokine produced by mast cells, basophils, ILC2 innate lymphoid cells, and activated CD4+ helper T cells; it drives IgE class-switching in B cells, mucus hypersecretion in airway epithelium, airway smooth-muscle hyperresponsiveness, and suppression of epidermal barrier proteins including filaggrin is one of the most consequential mediators of allergic inflammation. At chromosome 5q31.1, a cluster of interrelated variants spans the IL13 gene and nearby regulatory elements, forming a haplotype block that has emerged as one of the strongest and most consistently replicated genetic loci in allergy genetics.

rs1295686 is an intronic variant within IL13 located at chr5:132,660,151 (GRCh38). It does not change the IL-13 protein sequence — its significance lies in the haplotype it marks. The minor T allele co-segregates tightly with rs20541 (the missense variant that produces the hyperactive Q130 form of IL-13) and rs1295685 (a 3'-UTR regulatory variant linked to enhanced mRNA stability). Together, these three variants — plus rs848 and rs847 — define the IL13 risk haplotype block at 5q31.1 that has been linked to atopic dermatitis, asthma, allergic rhinitis, elevated serum IgE, and IgE-mediated food allergy across dozens of independent studies.

The Mechanism

As an intronic variant, rs1295686 does not alter IL-13 protein function directly. Luciferase reporter and chromosome conformation capture experiments22 Luciferase reporter and chromosome conformation capture experiments
Li et al. Am J Respir Cell Mol Biol 2022 — identified functional SNPs at the locus as rs1295685, rs848, and rs847, which form a haplotype that interacts with the promoter of TH2LCRR, a long non-coding RNA with elevated expression in asthma patients show that the causal functional effect at this locus operates through a haplotype interacting with TH2LCRR — a long non-coding RNA elevated in asthmatic airways. rs1295686 lies in strong linkage disequilibrium with this functional haplotype and with rs20541, which changes amino acid 130 of the IL-13 protein from arginine (R, lower receptor affinity) to glutamine (Q, higher receptor engagement and enhanced signaling through IL-13Rα1).

When the T allele at rs1295686 is present, the carrier almost invariably also carries the rs20541-A (Q130) and rs1295685-A risk alleles. The combined effect of these co-inherited variants is higher constitutive IL-13 pathway activity: elevated circulating IL-13 protein with enhanced receptor engagement drives persistent IgE production in B cells, mucus hypersecretion and airway hyperresponsiveness in the lung, and epidermal barrier disruption through STAT6-mediated suppression of filaggrin and loricrin in the skin.

The Evidence

The 5q31.1 IL13/RAD50 locus is among the most robust signals in atopy genetics. A 2023 European and multi-ancestry GWAS meta-analysis33 2023 European and multi-ancestry GWAS meta-analysis
Budu-Aggrey et al. Nature Communications; ~21,000 cases and ~95,000 controls in European discovery, 2.9 million in 23andMe replication placed the IL13/SLC22A5 5q31 locus at P<10⁻³⁶ for atopic dermatitis — one of the most significant signals in human atopy genetics. rs1295686 lies within this haplotype block.

For food allergy specifically, a challenge-confirmed pediatric cohort study44 challenge-confirmed pediatric cohort study
Ashley et al. Clin Exp Allergy 2017; discovery n=722 (367 food-allergic cases, 199 sensitized-tolerant, 156 controls) and replication n=533 (203 cases, 330 controls) found the T allele at rs1295686 associated with IgE-mediated food allergy at OR=1.75 (p=0.003) in discovery and OR=1.37 (p=0.03) in replication; the meta-analysis yielded OR=1.50 (p=0.0006). This study confirmed complete LD between rs1295686 and rs20541, establishing that the intronic tag and the coding functional variant travel together on the same risk haplotype.

For total serum IgE, a genome-wide association study in the Framingham Heart Study55 genome-wide association study in the Framingham Heart Study
Granada et al. J Allergy Clin Immunol 2012; 6,819 Framingham participants plus 5 independent replication cohorts identified rs1295686 as one of three loci reaching genome-wide significance (P=3.55×10⁻⁸) for elevated total plasma IgE — alongside FCER1A (the high-affinity IgE receptor) and STAT6 (the primary IL-13 downstream transcription factor).

For asthma, analyses in Chinese pediatric and adult cohorts66 Chinese pediatric and adult cohorts
Tang et al. Pediatr Allergy Immunol 2016; 903 asthmatic children, 1,205 controls; 479 adult asthmatics, 746 controls found rs1295686 associated with adult asthma (OR=1.64) and early-onset asthma (OR=1.92), confirming IL13 and GSDMB as replicated asthma genes. A study in Saudi Arabian adults77 Saudi Arabian adults
Halwani et al. J Asthma 2018 found the T allele at rs1295686 conferred OR=1.69 (p=0.008) for symptomatic asthma, extending the association beyond European ancestry.

The African-ancestry T allele frequency is markedly higher (~66%) than in Europeans (~20%), reflecting population-specific LD patterns. This does not translate directly into higher atopic disease rates, as gene-environment interactions differ, but it does mean the risk allele is substantially more common in individuals of African descent — a factor relevant to genetic counseling in diverse populations.

Practical Implications

Carrying one or two copies of the T allele at rs1295686 indicates membership in the IL-13 high-activity haplotype. The practical consequence is a higher baseline Th2 bias: more IL-13 activity, higher IgE production, and increased susceptibility to the full atopic triad (eczema, allergic rhinitis, asthma) and IgE-mediated food allergy. Measuring serum total IgE quantifies how biologically active this IL-13 pathway is in the individual.

For those with active atopic disease inadequately controlled by topical or standard therapies, the IL-13/IL-4 pathway is the genetically-indicated target. IL-13-specific biologics (tralokinumab) and IL-4Rα inhibitors (dupilumab) directly neutralize the cytokine pathway this haplotype overactivates. Skin barrier protection with ceramide emollients addresses the downstream consequence — filaggrin suppression — of high IL-13 signaling.

Interactions

rs1295686 lies in near-complete linkage disequilibrium with rs2054188 rs20541
IL-13 R130Q missense variant; Q130 form engages IL-13Rα1 with higher affinity, driving stronger JAK1/STAT6 signaling in B cells, airway epithelium, and skin keratinocytes and rs129568599 rs1295685
IL-13 3'-UTR variant affecting mRNA stability, on the same risk haplotype block. Carriers of the T allele at rs1295686 are thus almost invariably also carrying the rs20541-A and rs1295685-A risk alleles.

The downstream receptor partner for IL-13 signaling is IL-4Rα (encoded by IL4R, variant rs1801275). Carriers of both the IL-13 haplotype risk allele (rs1295686-T) and the IL4R risk allele may face compounding Th2 dysregulation — elevated IL-13 ligand activity meeting altered receptor signal transduction — with pharmacogenomic relevance to dupilumab response, which acts directly on the shared IL-4/IL-13 receptor subunit.

The upstream regulatory hub rs2040704 (in the RAD50/TH2LCRR region) coordinates expression of the IL-4/IL-5/IL-13 cytokine gene cluster. Combined risk allele status at both rs1295686 and rs2040704 may represent compounding Th2 amplification from different regulatory levels.

Genotype Interpretations

What each possible genotype means for this variant.

CC Baseline IL-13 Haplotype Normal

Common haplotype with standard IL-13 activity and typical atopic risk

You carry two copies of the C allele at rs1295686, the major allele found in approximately 64% of people of European descent and about 36% globally. The C allele represents the baseline IL-13 haplotype — not on the risk haplotype block containing the hyperactive Q130 form of IL-13 (rs20541) and the 3'-UTR regulatory variant (rs1295685). Your IL-13 signaling and IgE production are at population-average levels, and you do not carry the genetically-elevated atopic risk conferred by the T-allele haplotype.

CT IL-13 Risk Haplotype Carrier Intermediate

One copy of the IL-13 atopy risk haplotype — moderately elevated IgE and atopic disease susceptibility

As a CT heterozygote, you carry one copy of the IL-13 5q31 risk haplotype. This means one of your two IL13 gene copies produces the Q130 variant protein with higher IL-13Rα1 receptor engagement. The aggregate effect — one high-activity and one standard-activity copy — produces intermediate IL-13 pathway output. In the GWAS of total serum IgE (Granada et al. 2012, N=6,819 Framingham participants), rs1295686 reached genome-wide significance (P=3.55×10⁻⁸), with the dose-response showing heterozygotes intermediate between the two homozygote classes. A food allergy meta-analysis (Ashley et al. 2017, N=1,255) found OR=1.50 (p=0.0006) for IgE-mediated food allergy in T allele carriers overall. For asthma, OR=1.64 (adult) and OR=1.92 (early-onset) were reported in Chinese cohorts (Tang et al. 2016).

TT IL-13 Risk Haplotype Homozygote High Risk

Homozygous IL-13 atopy haplotype — highest IL-13 activity with substantially elevated risk for atopic disease and IgE-mediated allergy

As a TT homozygote at rs1295686, you carry two copies of the IL-13 5q31 risk haplotype. Every molecule of IL-13 produced from your IL13 gene copies carries the Q130 form with enhanced IL-13Rα1 receptor engagement, driving maximum downstream STAT6 activation. Combined with the 3'-UTR co-variant (rs1295685-AA), which may support higher transcript stability or translation rates, the TT genotype represents the apex of IL-13-driven Th2 polarization within this haplotype system. GWAS data show a clear additive dose-response at this locus across atopic conditions — the TT genotype sits at the high end of this gradient. Serum IgE in TT homozygotes is measurably elevated at baseline as a direct readout of sustained IL-13-driven B-cell IgE class-switching.

From a therapeutic standpoint, TT homozygotes with moderate-to-severe atopic disease represent the population biologically best matched to IL-13-targeted biologics (tralokinumab) or the dual IL-4/IL-13 inhibitor dupilumab. Both are approved for atopic dermatitis; dupilumab is also approved for asthma and chronic rhinosinusitis with nasal polyps. The GWAS of serum IgE reaching P=3.55×10⁻⁸ at this locus (Granada et al. 2012) and the OR=1.50 for food allergy (Ashley et al. 2017 meta-analysis) establish the magnitude of the biological effect, with TT homozygotes at the extreme end of the distribution.