Key Takeaways

• TNF-α is a major pro-inflammatory cytokine produced mainly by macrophages.
• It signals through two receptors, TNFR1 and TNFR2, with distinct effects.
• Downstream, TNF-α activates NF-κB to drive inflammation and cell survival, or triggers apoptosis.
• Excess TNF-α drives rheumatoid arthritis, inflammatory bowel disease and psoriasis.
• TNF inhibitors such as adalimumab and infliximab are cornerstone autoimmune therapies.
• TNF-α acts alongside cytokines such as IL-6 and IL-1β in the inflammatory response.

Contents

• What is TNF-alpha?
• The Function of TNF-alpha
• TNF Receptors and Signalling
• The TNF Signalling Pathway
• TNF-alpha in Inflammatory Disease
• Targeting TNF: TNF Inhibitors
• Frequently Asked Questions

TNF-alpha Pathway ELISA Kits

From TNF-α itself and its two receptors to the downstream transcription factor and partner cytokines, these validated ELISA kits cover the inflammatory pathway.

TNF-α

TNF-alpha ELISA Kit

CytokineHuman

The central pro-inflammatory cytokine of the innate immune response.

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TNFR1

Soluble TNFR1 (TNFRSF1A) ELISA Kit

ReceptorHuman

The death-domain receptor that drives both inflammation and apoptosis.

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TNFR2

Soluble TNFR2 (TNFRSF1B) ELISA Kit

ReceptorHuman

Expressed on immune cells, favouring survival and regulatory signals.

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NF-κB p65

NF-κB p65 (RelA) ELISA Kit

Transcription FactorHuman

The master switch TNF-α activates to turn on inflammatory genes.

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IL-6

IL-6 ELISA Kit

CytokineHuman

A downstream inflammatory cytokine induced by TNF-α signalling.

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IL-1β

IL-1 beta ELISA Kit

CytokineHuman

A partner cytokine amplifying the TNF-driven inflammatory cascade.

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What is TNF-alpha?

Tumour necrosis factor alpha (TNF-α) is a pro-inflammatory cytokine and a founding member of the TNF superfamily. It is produced chiefly by activated macrophages, but also by T cells, natural killer cells and others, in response to infection and tissue injury. It was named for its ability to trigger the death — necrosis — of certain tumour cells, but its true importance lies in its role as a master regulator of inflammation.

Structurally, TNF-α is first made as a membrane-bound protein that is cleaved by the enzyme TACE to release a soluble form. Both forms assemble into a homotrimer — three identical chains — and it is this trimeric molecule that binds and clusters its receptors to switch on signalling.

The Function of TNF-alpha

TNF-α orchestrates the body’s response to threat. It makes blood vessels more permeable and studded with adhesion molecules so that immune cells can leave the circulation and reach infected tissue, it activates macrophages and neutrophils, and it induces fever and the production of other inflammatory mediators. In short bursts this is a powerful and protective defence.

Sustained or excessive TNF-α, however, becomes damaging. Chronic production drives the tissue destruction seen in autoimmune disease and contributes to cachexia — the severe wasting associated with cancer and chronic infection.

TNF Receptors and Signalling

TNF-α acts through two distinct receptors. TNFR1 (TNFRSF1A) is expressed on almost all cell types and carries an intracellular death domain, allowing it to trigger both inflammation and programmed cell death. TNFR2 (TNFRSF1B) is largely restricted to immune and endothelial cells and tends to promote cell survival, proliferation and regulatory functions.

The two receptors also exist in soluble forms, shed from the cell surface, which can buffer circulating TNF-α — and which are useful biomarkers of TNF-pathway activity.

The TNF Signalling Pathway

When TNF-α clusters TNFR1, the receptor recruits adaptor proteins that build a signalling complex. This complex can follow two very different routes. In the survival route, it activates the transcription factor NF-κB (p65/RelA), which translocates to the nucleus and switches on genes for inflammation, immune activation and cell survival — including other cytokines such as IL-6 and IL-1β.

Alternatively, if NF-κB signalling is blocked, the complex assembles a death-inducing platform that activates caspases and drives the cell into apoptosis. The balance between these NF-κB survival and caspase death pathways determines whether a cell responds to TNF-α by mounting inflammation or by dying.

TNF-alpha in Inflammatory Disease

Because TNF-α is such a powerful driver of inflammation, its chronic overproduction is central to many autoimmune and inflammatory diseases. It is a key player in rheumatoid arthritis, where it fuels the joint destruction, in inflammatory bowel disease such as Crohn’s and ulcerative colitis, and in psoriasis and ankylosing spondylitis. In each, a self-sustaining loop of TNF-α and other cytokines perpetuates tissue damage.

Targeting TNF: TNF Inhibitors

The recognition of TNF-α as a central inflammatory driver led to one of the great success stories of modern medicine: TNF inhibitors. These biologic drugs — including the monoclonal antibodies adalimumab and infliximab, and the receptor-fusion protein etanercept — neutralise TNF-α or block its receptors, dramatically reducing inflammation.

TNF inhibitors have transformed the treatment of rheumatoid arthritis, inflammatory bowel disease and psoriasis, and remain among the best-selling drugs in the world. Because they suppress a key immune signal, they must be balanced against a raised risk of infection — a reminder of how central TNF-α is to normal defence.