rs2256774 — IL2RA

Intronic IL2RA variant independently associated with psoriasis susceptibility

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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 psoriasis connection is mechanistically coherent: psoriasis is a T-cell-driven inflammatory skin condition where Treg/Th17 imbalance88 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.99 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 GWAS1010 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.

Practical Implications

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.

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. 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 — intermediate autoimmune susceptibility

You carry one T risk allele and one protective C allele at rs2256774. 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 — susceptibility to psoriasis and other autoimmune conditions

You carry two copies of the T risk allele at rs2256774. 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.