rs1041981 — LTA Thr26Asn (TNFB*2)

Missense variant in lymphotoxin-alpha, a TNF superfamily cytokine essential for secondary lymphoid organ formation and innate immune coordination; the A allele (Asn at position 26 of mature protein) alters LTα trimer stability, modestly increases cancer susceptibility, and has been associated with coronary atherosclerosis and respiratory infection risk

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LTA Thr26Asn — When a Cytokine Blueprint Shifts Innate Defense

Lymphotoxin-alpha (LTα)11 Lymphotoxin-alpha (LTα)
a homotrimeric or heterotrimeric cytokine of the TNF superfamily, secreted mainly by activated lymphocytes and NK cells is one of the founding members of the immune signaling family that includes TNF itself. Unlike TNF, which is broadly expressed by macrophages and adipocytes, LTα is produced predominantly by lymphocytes and has a distinct but overlapping set of receptors and biological roles. Its two receptors — TNFR1 and TNFR2 — are shared with TNF, but LTα also forms heterotrimers with lymphotoxin-beta (LTβ) to activate the LTβ receptor, which directs lymphoid organogenesis. LTα is essential for the normal development of lymph nodes, Peyer's patches, and other secondary lymphoid structures, and it drives innate immune responses against bacteria, viruses, and transformed cells.

The rs1041981 variant — historically called the TNFB*2 allele — substitutes asparagine for threonine at position 26 of the mature protein (position 60 in the precursor, after a 34-residue signal peptide is cleaved). This change falls in the N-terminal "stalk" region of the LTα subunit, which is involved in receptor binding and trimer stability, and the A allele frequency is approximately 35% globally22 A allele frequency is approximately 35% globally, making it one of the more common functional variants in the TNF/LTA chromosomal region at 6p21.33.

The Mechanism

LTα is synthesized as a 205-amino-acid precursor. After signal peptide cleavage at position 34, the mature 171-amino-acid protein assembles into trimers that bind TNFR1 and TNFR2. The Thr26Asn change (mature protein numbering) introduces an asparagine in a region that contacts receptor ectodomains. UniProt annotation (P01374) classifies this as a natural variant at precursor position 6033 UniProt annotation (P01374) classifies this as a natural variant at precursor position 60, confirming the Asn substitution occurs in the trimer's receptor-binding interface area. The biological consequence is subtle rather than ablative — LTα-Asn26 is secreted normally and retains signaling function, but may alter binding affinity to TNFR1/TNFR2, modestly shifting the inflammatory set-point of cells responding to LTα. The rs1041981 A allele is in strong linkage disequilibrium with the adjacent intron variant rs909253 (r² ~0.92 in European populations), meaning the two frequently travel together on the same TNFB*2 haplotype block and their independent effects are difficult to fully disentangle.

The Evidence

The most quantitatively robust finding is in cancer susceptibility. A 2013 meta-analysis of 30 case-control studies covering 58,649 participants44 2013 meta-analysis of 30 case-control studies covering 58,649 participants
Huang et al., PLoS One found that the rs1041981 A allele conferred a statistically significant 15% elevation in cancer risk (OR 1.15, 99% CI 1.07–1.25, p < 0.0001). The association was seen across multiple cancer types, consistent with LTα's broad role in tumor immune surveillance through TNFR-mediated apoptosis and lymphocyte recruitment to tumor sites. A more targeted study in hepatocellular carcinoma (Alhelf et al., 2023, n = 317)55 (Alhelf et al., 2023, n = 317) confirmed the A allele was independently associated with HCC risk in an Egyptian case-control study.

In the cardiovascular domain, results are mixed. A 2012 autopsy study of 1,503 consecutive cases66 2012 autopsy study of 1,503 consecutive cases
Ikeda et al., Atherosclerosis found that AA + CA carriers had significantly greater coronary stenosis severity than CC homozygotes (OR 1.54, 95% CI 1.17–2.01), a pathological measure of subclinical atherosclerotic burden. However, the large ISIS case-control study of 6,928 MI cases77 ISIS case-control study of 6,928 MI cases
Clarke et al., PLoS Genetics 2006 found no significant association between LTA variants including rs1041981 and myocardial infarction occurrence, though higher CRP levels were seen in certain LTA haplotypes. This pattern — subclinical atherosclerosis association without a clear MI event signal — suggests rs1041981 may influence arterial inflammation and plaque development without necessarily precipitating acute coronary events.

For infectious disease, a 2017 study of Inuit populations88 2017 study of Inuit populations
Song et al., Scientific Reports found the A allele significantly associated with bronchitis risk, with the magnitude of risk modified by environment (westernized vs. rural lifestyle). A family-based analysis of 160 trio families99 family-based analysis of 160 trio families
Boraska et al., Human Immunology 2009 found significant overtransmission of the A allele to type 1 diabetes-affected offspring (p = 1.1×10⁻⁴), consistent with LTα's established role in pancreatic islet inflammation. The variant also sits within the same LTA/TNF haplotype block studied extensively for autoimmune diseases including rheumatoid arthritis, celiac disease, and multiple sclerosis, though rs1041981 itself is primarily a tag SNP for this region rather than the primary functional driver in all contexts.

Practical Actions

The rs1041981 A allele operates as a moderate risk modifier across several domains — cancer surveillance, subclinical atherosclerosis, and respiratory infection vulnerability — rather than a single-disease variant. Its effect size in each domain is modest (OR ~1.15–1.54 depending on the outcome), which means it does not warrant alarm but does point to specific monitoring strategies that can reduce the probability of adverse outcomes.

For A allele carriers, the most actionable implications relate to cancer screening adherence, cardiovascular inflammation monitoring, and attention to respiratory health. LTα's role in lymphoid tissue development and tumor immune surveillance means the A allele's modest risk operates through immune-modulating pathways rather than direct mutagenesis.

Interactions

The rs1041981 A allele resides within the classic HLA class III region1010 HLA class III region
a gene-dense segment of chromosome 6p21.33 housing TNF, LTA, and numerous immune-regulatory genes in strong LD. The adjacent intronic variant rs9092531111 rs909253
a commonly studied LTA intronic SNP in the same TNFB haplotype block travels with rs1041981 in ~92% of European haplotypes. The TNF promoter variant rs18006291212 rs1800629
TNF -308 G>A, the most studied TNF pathway polymorphism is in the same chromosomal neighborhood and occasionally studied in combined haplotype analyses with LTA variants. A combined LTA/TNF haplotype carrying both inflammatory alleles may produce additive effects on cytokine tone, though published compound analyses are limited for this specific pair.

Genotype Interpretations

What each possible genotype means for this variant.

CC LTα Wild-Type Normal

Common wild-type genotype — standard lymphotoxin-alpha inflammatory signaling

You carry two copies of the common C allele (threonine at position 26 of mature LTα). This is the reference configuration for lymphotoxin-alpha trimer assembly and receptor binding. About 42% of people globally share this genotype. Your LTα-mediated innate immune signaling operates at baseline, with no elevation in cancer susceptibility or cardiovascular inflammatory risk attributable to this variant.

AC LTα Variant Carrier Intermediate

One copy of the A allele — modestly elevated cancer and atherosclerosis inflammatory risk

The TNFB*2 haplotype (carrying the rs1041981 A allele) has been associated across multiple independent datasets with a pattern of heightened inflammatory signaling in lymphoid tissue. The biological mechanism is subtle — the Thr→Asn substitution near the receptor-binding interface of mature LTα may alter receptor affinity for TNFR1 and TNFR2, marginally shifting the dose-response for apoptosis signaling in lymphocytes and tumor cells.

The cancer meta-analysis (PMID 24349304) pooled 30 case-control studies and found consistent excess risk across cancer types (OR 1.15 per A allele, 99% CI 1.07–1.25), suggesting the effect operates via immune surveillance rather than tissue-specific biology. For atherosclerosis, the autopsy data (PMID 22310064) showing OR 1.54 for coronary stenosis in A-allele carriers reflects subclinical vascular inflammation rather than acute MI risk — consistent with LTα's role in arterial inflammatory signaling. Bronchitis and respiratory infection risk were elevated in A-allele carriers in an Inuit cohort, with the effect size modified by lifestyle environment.

AA LTα Homozygous Variant High Risk

Two copies of the A allele — highest rs1041981-associated cancer susceptibility and coronary inflammatory burden

The AA genotype represents the homozygous state of the TNFB*2 haplotype. At allele dose of 2, the Thr→Asn substitution at position 26 of mature LTα is present on both chromosomes, maximally shifting the variant's influence on TNFR1/TNFR2 signaling tone. The cancer meta-analysis (PMID 24349304) provides an overall OR of 1.15 per A allele — for AA homozygotes, this multiplicative model projects to approximately OR 1.32 for overall cancer susceptibility compared to CC. The coronary atherosclerosis autopsy study (PMID 22310064) grouped AA with CA carriers (OR 1.54 combined), and the fraction attributed to AA homozygotes alone is likely higher than this combined estimate.

LTα's role in type 1 diabetes is particularly notable — the A allele overtransmission signal (p = 1.1×10⁻⁴, PMID 19167443) suggests LTα-Asn26 alters the balance of lymphocyte-mediated pancreatic islet destruction. In AA homozygotes with family history of type 1 diabetes, this genetic context adds biological plausibility to closer metabolic monitoring.