rs1799724 — TNF -857C>T

TNF -857C>T: A Distinct Inflammatory Control Point

The TNF gene on chromosome 6p21.3 encodes tumor necrosis factor-alpha¹¹ tumor necrosis factor-alpha
a master cytokine controlling inflammation, immune cell activation, and apoptosis. The rs1799724 variant sits 857 base pairs upstream of the TNF transcription start site, within the gene's promoter — a regulatory region that controls how much TNF-alpha your immune cells produce. Unlike the well-studied -308 variant (rs1800629), the -857C>T polymorphism works through a distinct molecular mechanism and shows population-specific disease associations.

The Mechanism

The -857 position overlaps an OCT-1 binding site²² OCT-1 binding site
a binding site for octamer transcription factor-1, a protein that binds to DNA and regulates nearby gene expression. The T allele disrupts this binding site, altering the transcriptional regulation of TNF-alpha independently of the NF-κB binding site affected by the -308 variant. Because these two promoter polymorphisms operate via distinct transcription factor binding sites, they can produce additive or independent effects on TNF expression. The TNF gene is on the forward (plus) strand, so the C>T notation in papers corresponds directly to plus-strand alleles as reported in genome files.

The Evidence

The clearest disease association for the -857 T allele is in Asian populations with Crohn's disease³³ Crohn's disease
a chronic inflammatory bowel disease affecting the gastrointestinal tract. A meta-analysis of 31 studies found that Asians carrying the T allele had a 54% increased risk of Crohn's disease compared to CC carriers (OR 1.54, 95% CI 1.19–1.99). This ethnic specificity is notable — studies in European and Middle Eastern populations have not consistently replicated the IBD association, underscoring the importance of population context in interpreting this variant.

For psoriasis, a 2023 systematic review and meta-analysis⁴⁴ 2023 systematic review and meta-analysis
Sadafi et al., Heliyon found robust associations across five genetic models: the T allele conferred OR 1.57 in allelic comparison, and TT homozygotes showed OR 1.98 for psoriasis risk. This association was confirmed by trial sequential analysis, suggesting sufficient evidence for a genuine effect. The -857 variant is also among polymorphisms associated with psoriatic arthritis in a meta-analysis of 14 studies.

A clinically important finding concerns response to anti-TNF biologic drugs⁵⁵ anti-TNF biologic drugs
medications like infliximab, adalimumab, and etanercept that block TNF-alpha protein. A meta-analysis found that the common C allele — not the risk T allele — is associated with better response to TNF blockers (OR 1.78, 95% CI 1.13–2.80). Carriers of the T allele may therefore show reduced efficacy from anti-TNF biologics in conditions like Crohn's disease and spondyloarthropathy. A recent meta-analysis also links the T allele to increased type 1 diabetes susceptibility.

Practical Actions

For T allele carriers with active or suspected inflammatory bowel disease — particularly those of East Asian ancestry — this variant provides one more reason to pursue thorough gastroenterological evaluation. The -857 T allele adds biologically independent risk information beyond the more commonly tested -308 variant.

For T allele carriers with psoriasis or psoriatic arthritis, awareness of this genetic background may be relevant when discussing biologic therapy choices: if anti-TNF drugs are being considered, the -857 T allele predicts a somewhat less favorable response compared to C allele carriers. Switching to IL-17 or IL-23 inhibitors may be a better initial strategy.

Interactions

The -857 variant sits within a cluster of TNF promoter polymorphisms, including rs1800629⁶⁶ rs1800629
TNF -308 G>A, the most studied TNF promoter variant, rs1800630⁷⁷ rs1800630
TNF -863 C>A, and rs361525⁸⁸ rs361525
TNF -238 G>A. These SNPs are in partial linkage disequilibrium and can travel together on haplotypes; however, because they affect distinct transcription factor binding sites, each can contribute independent regulatory information. The combined effect of multiple TNF promoter variants on biologic drug response has been studied in Crohn's disease and psoriasis, and T allele carriers at -857 may compound the reduced anti-TNF response seen with A allele carriers at -308.