rs2256774 — IL2RA

Intronic IL2RA variant that modulates soluble IL-2RA shedding and Treg signaling; independently associated with psoriasis susceptibility and contributes to the IL2RA locus autoimmune risk signal

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IL2RA rs2256774 — A Second Dial on the Treg Thermostat

The IL2RA gene11 IL2RA gene
IL2RA encodes CD25, the alpha chain of the high-affinity IL-2 receptor, essential for regulatory T cell (Treg) development and homeostasis harbors multiple independent regulatory variants that together determine how finely tuned your immune system's self-tolerance machinery is. rs2256774 is an intronic variant in IL2RA that operates in the same regulatory neighbourhood as the better-studied rs210428622 rs2104286
rs2104286 is the index IL2RA MS/T1D risk variant affecting intron-1 methylation and soluble IL-2RA shedding, but contributes an independent signal. Fine-mapping studies of the IL2RA locus in multiple sclerosis have shown that rs2256774 and rs3118470 together provide the best genotype discrimination for MS risk33 rs2256774 and rs3118470 together provide the best genotype discrimination for MS risk
Babron et al. demonstrated a combined relative risk of 3.54 between least- and most-at-risk genotype combinations at these two SNPs. The same locus has been identified in a genome-wide association study of psoriasis44 genome-wide association study of psoriasis
GWAS Catalog GCST, beta=0.068, p=1×10⁻⁹ for psoriasis susceptibility at rs2256774, extending IL2RA's role across skin-directed and systemic autoimmune diseases.

The Mechanism

IL-2 signaling through the high-affinity receptor complex (CD25/CD122/CD132) is the master maintenance signal for Treg viability and function55 master maintenance signal for Treg viability and function
IL-2R stimulation drives pSTAT5, which transcribes FoxP3 and anti-apoptotic genes essential for Treg identity and survival. Intronic variants in IL2RA alter the balance between membrane-anchored CD25 — which captures IL-2 for Treg activation — and soluble IL-2RA (sIL-2RA), a shed ectodomain fragment that acts as a decoy receptor66 acts as a decoy receptor
sIL-2RA binds IL-2 with moderate affinity, sequestering it in serum and reducing availability for membrane-bound Treg receptors. When sIL-2RA is elevated, Tregs are present in normal numbers but receive insufficient IL-2 stimulation — a functionally hyporeactive state that impairs suppression of autoreactive T cells.

The IL2RA locus demonstrates allelic heterogeneity77 allelic heterogeneity
Different variants at the same locus have distinct effects; one allele may preferentially associate with MS, another with T1D, and a third with both diseases. rs2256774 represents one node in this network: its T allele is associated with increased autoimmune susceptibility, while the C allele is protective. The mechanism parallels rs210428688 mechanism parallels rs2104286
rs2104286 alters allele-specific CpG methylation in intron-1, increasing IL2RA transcription and sIL-2RA shedding, though rs2256774 may act through a distinct regulatory element within the same gene.

The psoriasis connection is mechanistically coherent: psoriasis is a T-cell-driven inflammatory skin condition where Treg/Th17 imbalance99 Treg/Th17 imbalance
In psoriatic plaques, reduced Treg suppressive capacity allows Th17 and Th1 effector cells to drive IL-17A and TNF-alpha production is a central driver of keratinocyte hyperproliferation. Impaired Treg function from IL2RA variants creates a permissive environment for psoriatic inflammation.

The Evidence

The most direct evidence for rs2256774's clinical relevance comes from two sources. In MS genetics, Babron et al.1010 Babron et al.
Babron MC et al. "Determination of the real effect of genes identified in GWAS: the example of IL2RA in multiple sclerosis." EJHG 2012 analysed 26 IL2RA variants in 522 MS trio families and 244 affected sib-pairs, finding that the two-SNP combination of rs2256774 and rs3118470 outperformed any single variant in discriminating case from control genotype distributions (p-corrected=0.009). The relative risk between least and most at-risk genotype combinations reached 3.54 (95% CI: 2.14–5.94) — a substantially larger effect than the modest single-SNP ORs typically observed at GWAS loci, suggesting that rs2256774 and rs3118470 together tag a haplotype with genuine functional consequence.

The 2007 NEJM MS GWAS1111 2007 NEJM MS GWAS
International Multiple Sclerosis Genetics Consortium. "Risk alleles for multiple sclerosis identified by a genomewide study." NEJM 2007 identified IL2RA as a genome-wide significant MS risk locus (p=2.96×10⁻⁸) in 12,360 subjects, establishing the locus-level evidence that rs2256774 fine-mapping built upon. The psoriasis association (beta=0.068, p=1×10⁻⁹) represents an independent discovery across a different autoimmune phenotype, corroborating IL2RA's role in skin immune dysregulation.

Functional confirmation comes from Cerosaletti et al.1212 Cerosaletti et al.
Cerosaletti K et al. "Multiple autoimmune-associated variants confer decreased IL-2R signaling in CD4+CD25hi T cells." PLoS One 2013, who showed that IL2RA risk haplotype carriers demonstrate reduced pSTAT5 in CD4+CD25hi T cells despite normal or increased surface CD25, confirming the sIL-2RA shedding mechanism at the cellular level.

Practical Implications

Because rs2256774 modulates the same IL-2R axis as rs2104286, the actionable interventions overlap: strategies that strengthen Treg function through IL-2-independent pathways are particularly relevant for T-risk-allele carriers.

Vitamin D is a key intervention because 1,25-dihydroxyvitamin D3 drives Treg differentiation through VDR/TGF-beta1 signaling, providing a backup pathway when IL-2 access is limited. Omega-3 fatty acids (EPA in particular) reinforce Treg polarization through PPAR-gamma activation while DHA-derived specialized pro-resolving mediators suppress Th17 differentiation — directly countering the Treg/Th17 imbalance that drives psoriatic inflammation.

For psoriasis-specific monitoring, T-allele carriers should pay attention to skin changes suggestive of psoriasis onset — plaques on elbows, knees, scalp, or the lower back — and to triggers that precipitate flares in genetically susceptible individuals (streptococcal infections, certain medications, stress-induced immune dysregulation).

Interactions

rs2256774 operates within the broader IL2RA regulatory network. [Within the locus | Fine-mapping demonstrates at least three partially independent IL2RA signals in autoimmune disease], it acts in combination with rs3118470 and independently from rs2104286, together determining the magnitude of IL-2 signaling attenuation. Carriers of risk alleles at multiple IL2RA SNPs simultaneously may show additive impairment of Treg function.

Cross-locus interactions with CTLA4 rs3087243 are biologically plausible: CTLA4 delivers co-inhibitory signals that complement Treg suppression, and simultaneous impairment of both IL-2R signaling (rs2256774) and CTLA4 co-inhibition (rs3087243) could produce converging Treg dysfunction. These interactions belong in compound action analysis — individual recommendations here address each variant in isolation.

Genotype Interpretations

What each possible genotype means for this variant.

CC Optimal IL-2R Function Normal

Two protective alleles — lowest IL2RA autoimmune risk from this locus

You carry two copies of the protective C allele at rs2256774. This genotype is associated with lower soluble IL-2RA shedding and intact IL-2 signaling to your regulatory T cells, supporting effective immune self-tolerance. About 13% of Europeans carry this genotype. Your baseline autoimmune and psoriasis risk from this IL2RA variant is at the lowest level. In East Asian populations this genotype is rare (~1.7%) given the very high T-allele frequency (86.9%) in those populations.

CT Intermediate IL-2R Function Intermediate

One risk allele — modestly elevated sIL-2RA and intermediate autoimmune susceptibility

You carry one T risk allele and one protective C allele at rs2256774. This heterozygous state is associated with intermediate soluble IL-2RA levels, creating partial competition between shed decoy receptors and membrane-bound Treg receptors for available IL-2. About 46% of Europeans share this genotype. In combination with rs3118470 status, this variant contributes to the IL2RA locus risk signal for multiple sclerosis and psoriasis — the psoriasis GWAS effect size is beta=0.068 per T allele (p=1×10⁻⁹), indicating a modest but statistically robust effect at population scale.

TT Reduced IL-2R Function High Risk

Two risk alleles — elevated sIL-2RA impairs Treg signaling and increases susceptibility to psoriasis and other autoimmune conditions

You carry two copies of the T risk allele at rs2256774, associated with the highest level of soluble IL-2RA shedding from this variant and the greatest attenuation of Treg IL-2 signaling. About 41% of Europeans and 75% of East Asians carry this genotype. The psoriasis GWAS identifies the T allele with beta=0.068 per allele (p=1×10⁻⁹), meaning TT homozygotes carry the maximum effect from this variant. When combined with risk status at rs3118470, the relative risk between least and most at-risk genotypes reaches 3.54 (95% CI: 2.14–5.94) for multiple sclerosis. The Treg/Th17 imbalance driven by impaired IL-2 signaling is a central mechanism in psoriatic inflammation, linking your immune regulation genotype directly to skin disease risk.