IL1RL1 rs3771180: Allergy and Asthma Genetics
The genetic variant rs3771180 is a single nucleotide polymorphism located within the IL1RL1 gene locus on chromosome 2. Research connects this regulatory variant to differences in immune signaling, specifically influencing blood eosinophil counts, allergic rhinitis, and susceptibility to atopic asthma. However, its overall clinical effect size is modest, representing statistical risk rather than a definitive medical outcome.
What each genotype means
Typical IL1RL1 expression profile
This genotype represents the common homozygous state for this regulatory variant. Research indicates that variants in the IL1RL1 locus are associated with the regulation of eosinophil counts and susceptibility to atopic conditions like allergic rhinitis, though the specific functional impact of this genotype remains limited in clinical literature. This information is for educational purposes and does not constitute a medical diagnosis.
This genotype is common in populations of European ancestry, where the minor allele frequency is approximately 0.40.
Heterozygous IL1RL1 variant profile
Carrying one copy of each allele is a common occurrence for this regulatory variant. While the IL1RL1 gene is known to influence inflammatory pathways and atopic disease susceptibility, the specific contribution of this heterozygous state to individual health outcomes is not fully established. Please consult with a healthcare professional if you have concerns regarding allergic conditions or immune health.
This genotype is frequently observed in diverse populations, reflecting the high prevalence of both alleles in many ancestral groups.
Alternative IL1RL1 expression profile
This genotype represents the homozygous state for the alternative allele at this regulatory locus. Studies suggest that genetic variation in IL1RL1 is linked to the modulation of immune responses and atopic traits, but the evidence regarding the specific clinical significance of this genotype is limited. This profile should not be used to infer personal health status or risk for allergic disease.
This genotype is found at varying frequencies globally, with higher prevalence in populations where the minor allele is more common.
Genetic Architecture: What Is rs3771180?
The single nucleotide polymorphism rs3771180 is situated on chromosome 2 in the genomic region harboring the interleukin 1 receptor-like 1 (IL1RL1) gene. This gene locus is central to the regulation of type 2 inflammatory pathways. Rather than directly disabling or mutating the protein sequence, rs3771180 functions primarily as a regulatory or tagging variant within a broader linkage disequilibrium block. Regulatory variants in this region frequently act as expression quantitative trait loci (eQTLs), influencing the efficiency of gene transcription or alternative splicing. Consequently, possessing alternate alleles at this locus can shift the basal balance of inflammatory mediators produced by the immune system, subtly modifying how mucosal barriers and immune cells respond to inhaled allergens or environmental irritants.
The Biological Role of the IL1RL1 Gene
The IL1RL1 gene encodes the ST2 receptor, a vital component of the interleukin-33 (IL-33) signaling pathway. ST2 exists in two primary isoforms: a membrane-bound receptor (ST2L) expressed on mast cells, Th2 lymphocytes, and eosinophils, and a truncated soluble decoy receptor (sST2) that circulates in bodily fluids. When the 'alarmin' cytokine IL-33 is released from damaged airway epithelial cells, it binds to ST2L, initiating a cascade that triggers eosinophilic inflammation and allergic immune responses. In contrast, sST2 neutralizes circulating IL-33 by acting as an inhibitory sink. Genetic variations in the IL1RL1 locus alter the balance between these two isoforms, which can either amplify or dampen allergic sensitization and type 2 inflammation throughout the respiratory and mucosal tracts.
Associated Traits: Asthma, Eosinophils, and Allergies
Genome-wide association studies cataloged by resources like the GWAS Catalog consistently implicate the IL1RL1 locus in respiratory and allergic phenotypes. Researchers have identified associations between rs3771180 and related linked markers with blood eosinophil levels, allergic rhinitis (hay fever), and atopic asthma. Elevated eosinophil counts are hallmark indicators of airway hypersensitivity and allergic diseases. However, evidence strength for rs3771180 acting as a sole driver is categorized as limited because common respiratory traits are highly polygenic. Many genes work in concert alongside non-genetic factors. Therefore, while carrying specific alleles is statistically correlated with a higher probability of allergic symptoms or altered eosinophil numbers, it does not cause disease in isolation.
Ancestry and Population Distribution
Allele frequencies for rs3771180 vary across different ancestral backgrounds, a common characteristic of ancient regulatory variants in human immune genes. According to major population genomics databases like gnomAD and the 1000 Genomes Project, the minor allele frequency (MAF) is approximately 0.40 among populations of European ancestry. In individuals of African ancestry, the minor allele frequency is around 0.25. These frequency discrepancies mean that the baseline distribution of genotypes shifts noticeably across geographic regions. Because genetic background and environmental allergen exposures differ significantly around the globe, statistical associations identified primarily in European cohorts may carry different predictive value or relative effect sizes when evaluated in other ancestries.
How to Interpret Your Results
Finding your genotype at rs3771180 provides educational insight into your personal genome, but it cannot be used as a medical diagnosis. Genetic variants in the IL1RL1 pathway confer modest statistical shifts in relative risk, not clinical certainties. An individual carrying alleles linked to higher allergic sensitivity may never develop asthma, while someone with a protective genetic profile may still experience severe allergies due to environmental exposures, infections, or other genetic variants. Furthermore, this variant should never guide personal medical decisions or changes to asthma therapy. If you have concerns regarding respiratory symptoms, hay fever, or existing inhaler prescriptions, discuss them directly with a licensed physician or clinical allergist.
How common is this variant?
The minor allele frequency for rs3771180 is approximately 0.40 in European ancestry cohorts and around 0.25 in individuals of African ancestry.
Frequently asked questions
Does having the rs3771180 risk genotype mean I will definitely develop asthma?
No. The rs3771180 variant only slightly influences your statistical odds and is not a deterministic or causal mutation. Most individuals who carry risk-associated alleles at this locus never develop asthma or chronic allergic conditions.
Can I use my rs3771180 genotype to change my asthma inhaler or allergy medication?
No, you should never alter your medical regimen based on direct-to-consumer genetic markers. Any adjustments to allergy medications, inhalers, or biologics must be supervised by your healthcare provider.
What is the biological connection between IL1RL1 and eosinophils?
IL1RL1 encodes the ST2 receptor, which detects interleukin-33 released during airway inflammation. Signaling through ST2 stimulates immune cells that promote the survival and activation of eosinophils, leading to variable eosinophil counts in the bloodstream.
Why do allele frequencies for rs3771180 vary across different ancestral groups?
Human populations evolved in distinct geographical environments with differing exposures to pathogens, parasites, and climate factors. Over millennia, natural selection and genetic drift led to variations in the baseline frequencies of immune-related alleles across world populations.
Sources & further reading
Educational information only, last refreshed 9/8/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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An intergenic regulatory variant upstream of IL1RL1 that influences circulating soluble ST2 levels and severity of allergic rhinitis.
This variant in the IL1RL1/IL18R1 locus influences ST2 receptor expression and modifies individual susceptibility to allergic sensitization and asthma.
Intronic regulatory variant in the IL1RL1/IL18R1 cluster modulating ST2 receptor expression and inflammatory disease risk.
ST2/interleukin-1 receptor-like 1 variant associated with altered IL-33 signaling and heightened risk for allergic asthma and atopy.
Intronic regulatory SNP in IL1RL1/ST2 associated with sST2 expression levels and susceptibility to allergic sensitization and asthma.
Variant in IL1RL1 (ST2) associated with allergic inflammation and cytokine production.