rs1143634 — IL1B +3954C>T

IL-1β +3954C>T — A Silent Mutation That Amplifies Inflammation

Interleukin-1 beta (IL-1β) is one of the most potent pro-inflammatory cytokines in the human immune system¹¹ one of the most potent pro-inflammatory cytokines in the human immune system
IL-1β activates NF-κB signaling, drives fever, induces acute phase proteins, promotes neutrophil recruitment, and directly stimulates bone resorption — all fundamental to both protective immunity and inflammatory disease. The IL1B gene encodes this cytokine on chromosome 2, and the rs1143634 variant at exon 5 position +3954 presents an unusual biological puzzle: a synonymous mutation — one that preserves the amino acid sequence — that nonetheless changes how much IL-1β protein the body produces²² a synonymous mutation — one that preserves the amino acid sequence — that nonetheless changes how much IL-1β protein the body produces
The F105F substitution (Phe→Phe) is silent at the protein level but functionally loud at the secretion level.

The Mechanism

The +3954C>T variant (rs1143634) is located in exon 5 of IL1B, in the region encoding the mature IL-1β protein's domain critical for receptor binding. Despite causing no amino acid change at position 105 (phenylalanine is retained regardless of C or T), carriers of the T allele produce substantially more IL-1β protein after immune stimulation³³ carriers of the T allele produce substantially more IL-1β protein after immune stimulation
In a study of aseptic implant loosening, T allele carriers had plasma IL-1β levels of 11.79 pg/mL versus 2.11 pg/mL in CC homozygotes after stimulation — a 5.6-fold difference.

The mechanism by which a synonymous codon change alters protein secretion likely operates at the post-transcriptional level. Synonymous variants can alter mRNA secondary structure, codon usage optimization, or regulatory element binding within the coding sequence⁴⁴ alter mRNA secondary structure, codon usage optimization, or regulatory element binding within the coding sequence
These effects can influence mRNA stability, translation efficiency, or protein folding — and for IL-1β, which requires caspase-1 cleavage for secretion, subtle conformational changes in the precursor protein could plausibly accelerate or facilitate the secretion process. In vitro studies show that the T allele leads to measurably higher IL-1β release from lipopolysaccharide-stimulated immune cells compared to the C allele.

This variant is distinct from the better-known promoter variants in IL1B: rs16944 (-511C>T) and rs1143627 (-31T>C)⁵⁵ rs16944 (-511C>T) and rs1143627 (-31T>C)
These two promoter variants regulate IL-1β transcription; rs1143634 instead appears to affect post-translational secretion or processing, providing an independent second tier of IL-1β output control. A person who carries high-producing alleles at multiple IL1B loci may have compounded elevation of IL-1β output.

The Evidence

The strongest and most consistent evidence links rs1143634 to periodontal disease. A meta-analysis of 54 case-control studies encompassing 9,376 participants⁶⁶ meta-analysis of 54 case-control studies encompassing 9,376 participants
Association between the rs1143634 polymorphism in interleukin-1B and chronic periodontitis. Journal of Periodontal Research, 2018 found the T allele significantly associated with chronic periodontitis risk (OR 1.35, 95% CI 1.24–1.48; p < 0.00001). Stratified analyses confirmed the association in Caucasian, Asian, and mixed populations, though not in African ancestry cohorts.

The aseptic joint loosening study⁷⁷ aseptic joint loosening study
IL-1β gene (+3954C/T) and NOS2 polymorphisms associate with early aseptic loosening of arthroplasties. Scientific Reports, 2022 provided some of the most compelling functional evidence: patients with the TT genotype showed a 3.7-fold higher hazard of requiring revision surgery within 5 years (HR 3.70, 95% CI 1.27–10.75), with the elevated IL-1β levels directly driving peri-implant bone resorption. This study confirmed the secretion phenotype rather than just disease association.

For cancer risk, an updated meta-analysis of 44 studies (18,645 cancer patients, 22,882 controls)⁸⁸ updated meta-analysis of 44 studies (18,645 cancer patients, 22,882 controls)
Role of IL-1β rs1143634 (+3954C>T) polymorphism in cancer risk. International Journal of General Medicine, 2021 found the T allele associated with modestly elevated overall cancer risk (allelic model OR 1.08). Gastric cancer, breast cancer, and multiple myeloma showed the most consistent signals in subgroup analyses.

In inflammatory bowel disease, IL1B gene polymorphisms including the exon 5 variant were shown to influence the course and severity of IBD in a study of 96 UC and 98 Crohn's patients⁹⁹ IL1B gene polymorphisms including the exon 5 variant were shown to influence the course and severity of IBD in a study of 96 UC and 98 Crohn's patients
IL1B gene polymorphisms influence the course and severity of inflammatory bowel disease. Gut, 2000, establishing a role for this variant in gastrointestinal inflammatory disease progression rather than susceptibility alone.

A notable negative finding: the T allele is not associated with aggressive periodontitis (OR 0.99, 95% CI 0.79–1.23 in a 25-study meta-analysis) — the association is specific to chronic periodontitis. This distinction matters clinically: aggressive and chronic periodontitis have different etiologies and risk profiles, and the IL-1β elevation associated with this variant appears to drive the sustained chronic inflammatory pattern rather than acute-onset aggressive disease.

Practical Actions

Elevated IL-1β production from this variant is not inevitably harmful — it is a quantitative trait that becomes clinically relevant under specific conditions. The most actionable implications:

Dental health: Carriers of one or two T alleles have meaningfully elevated periodontal risk. The T allele is particularly dangerous in combination with smoking, where the risk amplifies substantially. The variant provides a genetic basis for prioritizing periodontal care beyond standard recommendations.

Inflammatory conditions: Elevated baseline IL-1β production may accelerate inflammation-driven tissue damage in contexts ranging from joint prostheses to gastrointestinal mucosa. Conditions where IL-1β is a known mediator — including gout, IBD flares, and peri-implant inflammation — may be more severe in T allele carriers.

Cancer context: The modest cancer risk elevation (OR ~1.08) is not sufficient to change standard screening protocols, but it reinforces the importance of anti-inflammatory strategies and standard cancer screening adherence.

Interactions

rs1143634 is part of the IL1B locus on chromosome 2q14.1, which also encodes IL1A, and is co-located with the IL1RN gene encoding the IL-1 receptor antagonist. The promoter variants rs16944 (−511) and rs1143627 (−31) regulate IL-1β transcription via different mechanisms from rs1143634. A person carrying risk alleles at both the promoter level (rs16944) and the exon 5 level (rs1143634) may have compounded IL-1β output — both more transcript and more efficient secretion of the protein.

Interaction with IL1RN rs419598 (the IL-1 receptor antagonist gene) is biologically important: IL-1Ra counterbalances IL-1β by competing for the IL-1 receptor without signaling. Carrying the rs1143634 T allele (high IL-1β) alongside low-producing IL-1Ra variants may amplify net IL-1 signaling substantially.

The composite IL-1 genotype combining IL1A rs1800587 and IL1B rs1143634 was shown to have a 2.84-fold risk of chronic periodontitis in smokers (OR 4.43 in male smokers, OR 6.00 in female smokers)¹⁰¹⁰ a 2.84-fold risk of chronic periodontitis in smokers (OR 4.43 in male smokers, OR 6.00 in female smokers)
Interaction of IL1B and IL1RN polymorphisms, smoking, gender and ethnicity with aggressive and chronic periodontitis susceptibility. J Clin Periodontol, 2016, illustrating that single-variant effects are substantially potentiated in this combined context.