rs2070874 — IL4 IL4 C-33T

5'-UTR variant 33 bases downstream of the IL-4 transcription start site; the T allele alters local RNA secondary structure and is associated with elevated IL-4 production, raised serum IgE, and increased susceptibility to allergic asthma and allergic rhinitis through amplified Th2-skewed immune responses

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IL4 C-33T — The 5'-UTR Rheostat of Th2 Immunity

Interleukin-411 Interleukin-4
IL-4 is the master Th2 cytokine secreted by activated CD4+ T cells, mast cells, basophils, and innate lymphoid cells type 2 (ILC2s); it drives naïve T cell polarization toward the Th2 phenotype, instructs B cells to switch antibody class to IgE, and maintains mast cell and eosinophil survival is the central regulator of the allergy-prone immune state. The IL4 gene sits on chromosome 5q31.1, a region long known to harbour susceptibility loci for atopic disease. rs2070874 is a C-to-T substitution 33 bases into the 5'-untranslated region (5'-UTR) of the IL4 transcript — between the transcription start site and the protein-coding start codon. At this position, the variant does not change the IL-4 protein but alters the RNA sequence in a way that influences how efficiently the mRNA is translated and, indirectly, how much IL-4 protein is ultimately produced.

The Mechanism

The 5'-UTR is not silent. It contains secondary structures (hairpin loops, internal ribosome entry elements, and upstream open reading frames) that regulate ribosome access and translation efficiency. A single-nucleotide change in this region can flatten or deepen a hairpin that otherwise impedes ribosomal scanning, raising the rate at which ribosomes reach the main IL-4 coding sequence. The T allele at position +33 is associated with higher IL-4 plasma levels in genotype-stratified studies — an association documented in multiple genotype-stratified studies — T allele carriers consistently show higher in-vivo IL-4 plasma levels than CC homozygotes, a relationship that is amplified when the T allele at this 5’-UTR site co-occurs with the IL4 VNTR allele-1 on the same haplotype (Bibert et al., Immunogenetics 201522 (Bibert et al., Immunogenetics 2015
doi:10.1007/s00251-015-0836-3). The rs2070874 variant is also in strong linkage disequilibrium with rs2243250, the -589C>T promoter SNP. The two variants co-segregate on the same haplotype — the T alleles at both sites tend to be inherited together, and together they confer higher IL-4 transcription (rs2243250 effect via NFAT-1 binding) plus potentially higher translation efficiency (rs2070874 5'-UTR effect). The combined haplotype represents the most biologically active IL-4 configuration.

The Evidence

The strongest evidence for rs2070874 comes from a 2020 meta-analysis of 24 publications33 2020 meta-analysis of 24 publications
Imani et al., BMC Medical Genetics — 28 studies pooling 6,587 asthma cases and 8,408 controls with searches in Web of Science, Scopus, and PubMed. In the overall population, the T allele was a significant risk factor under all genotype models tested. Ethnicity- specific analysis found the association significant in Europeans across all models except heterozygote comparison, and in Americans and Asians across several models. Age-stratified analysis confirmed T allele risk in pediatric, adult, and mixed-age cohorts under the allelic model. An earlier 2014 meta-analysis44 2014 meta-analysis
Zheng et al. independently confirmed the -33C/T polymorphism as an asthma risk factor across ethnically diverse studies.

The direct IgE link was established in early work by Howard et al. 200155 Howard et al. 2001, who associated the C+33T polymorphism directly with elevated total serum IgE in atopic cohorts.

Beyond classic atopy, a 2022 haplotype analysis66 2022 haplotype analysis
Junta et al., Genes of 195 patients demonstrated that the IL4 haplotype containing the rs2070874 T allele was significantly associated with NSAID-exacerbated respiratory disease (AERD/N-ERD) — the severe aspirin-sensitive asthma phenotype defined by nasal polyps, eosinophilic inflammation, and reactions to COX-1 inhibitors. This finding extends the IL4 5'-UTR variant's clinical footprint from common atopy to the most refractory eosinophilic asthma phenotype.

Evidence level: strong. Meta-analyses replicate across multiple ethnicities, ages, and atopic disease phenotypes; the biology (5'-UTR regulation of translation, plasma IL-4 elevation, serum IgE elevation) is mechanistically coherent.

Practical Actions

For T allele carriers, the elevated IL-4 output means: (1) total serum IgE is a directly informative biomarker — T allele carriers' IgE trends higher, and periodic measurement reveals whether the IL-4 pathway is biologically active; (2) quercetin and related flavonoids suppress IL-4 and IL-13 gene transcription in activated T cells with mechanistic specificity to this pathway; (3) for TT homozygotes with active moderate-to-severe atopic disease, dupilumab (which blocks the IL-4Rα receptor used by both IL-4 and IL-13) is the biologically best-matched therapy; (4) aspirin and NSAIDs warrant caution in T allele carriers with asthma, given the haplotype association with NSAID-exacerbated respiratory disease.

Interactions

rs2070874 is in strong linkage disequilibrium with rs2243250 (IL4 -589C>T) — the two T alleles co-segregate on the same haplotype. Carriers of both T alleles have the highest constitutive IL-4 output from combined promoter-level (NFAT-1 binding enhancement) and 5'-UTR-level (translation efficiency) effects. Haplotype-level analysis consistently shows stronger disease associations for the T/T haplotype at both sites than for either variant alone.

The rs1801275 variant (IL-4Rα Arg576Gln) alters the cytoplasmic signalling domain of the shared IL-4/IL-13 receptor chain. When elevated IL-4 production (rs2070874 T allele) meets altered receptor signal transduction (rs1801275), Th2 pathway output may be doubly amplified — a biologically plausible interaction that is relevant to dupilumab pharmacogenomics.

The rs20541 variant (IL-13 Arg130Gln) elevates IL-13 output through a separate gene but shares the IL-4Rα signalling chain. Carriers of both rs2070874-T and rs20541-A face combined Th2 cytokine over-activity from both arms of the IL-4/IL-13 axis — the combination that dupilumab is designed to block at the receptor level.

Genotype Interpretations

What each possible genotype means for this variant.

CC Baseline IL-4 5'-UTR Normal

Standard 5'-UTR configuration with typical IL-4 translation efficiency and normal atopic risk

The CC genotype confers the population-typical IL-4 translational output. The 5'-UTR at this position does not contain a T allele that could flatten an inhibitory secondary structure or otherwise boost ribosome access to the IL-4 coding sequence. Studies stratifying by this genotype show that CC individuals have the lowest IL-4 plasma levels and the lowest IL-4-driven IgE burden among the three genotypes, consistent with baseline Th2 tone. No specific genotype-driven interventions are warranted at this locus for CC carriers. Common environmental triggers and other genetic variants remain the dominant determinants of individual atopic risk.

CT Elevated IL-4 5'-UTR Activity Intermediate

One T allele modestly elevates IL-4 production and raises atopic disease susceptibility

The single T allele creates an intermediate IL-4 output state. Mechanistically, one copy of the 5'-UTR carries the altered nucleotide that may improve ribosome access to the IL-4 coding sequence; the other copy retains the reference configuration. Studies directly measuring IL-4 plasma levels by rs2070874 genotype show a dose-dependent relationship — CT > CC — confirming that one T allele confers measurable functional elevation even without homozygosity. Because rs2070874-T co-segregates with the rs2243250-T promoter allele on the same haplotype, CT carriers also tend to carry one copy of the NFAT-1-enhanced promoter allele, compounding the translational effect with a transcriptional boost from the same chromosome. The practical consequence is a moderately Th2-biased immune state: IgE production is elevated above the CC baseline, sensitization to allergens is more efficient, and asthma and rhinitis risk are modestly increased across the large meta-analysis evidence base.

TT High IL-4 5'-UTR Activity High Risk

Two T alleles maximally amplify IL-4 production, driving high IgE and the strongest Th2 immune skew at this locus

With two T alleles, both copies of the IL4 5'-UTR carry the altered sequence associated with enhanced translation efficiency. Both chromosomes also carry the rs2243250 T allele (through linkage disequilibrium), meaning that TT homozygotes here are virtually always TT homozygotes at the IL4 promoter as well. The cumulative effect is the highest constitutive IL-4 output from this gene locus: maximum NFAT-1-driven transcription from both alleles (rs2243250 effect) combined with maximum 5'-UTR translational efficiency from both alleles (rs2070874 effect). IL-4 at this level drives vigorous B-cell IgE class-switching, strong Th2 polarization of naïve T cells, amplified mast cell and eosinophil activation, and direct skin barrier disruption through STAT6-mediated suppression of filaggrin and loricrin. From a therapeutic standpoint, TT homozygotes with moderate-to-severe atopic disease are the population biologically best matched to dupilumab, which targets IL-4Rα to block both IL-4 and IL-13 signalling simultaneously. The association with NSAID-exacerbated respiratory disease via the IL4 haplotype means aspirin sensitivity testing is relevant for any TT carrier with asthma, nasal polyps, or chronic eosinophilic sinusitis.