Soluble tumor necrosis factor receptor I (sTNFR1)

Soluble tumor necrosis factor receptors I and II are the extracellular domains cleaved from their respective membrane-bound forms—tumor necrosis factor receptor type I (55 kDa) and type II (75 kDa). These soluble forms circulate in body fluids where they retain the ability to bind tumor necrosis factor-alpha (TNFα), albeit with lower affinity than their membrane-bound counterparts. By binding free TNFα in circulation, they act as natural modulators that can buffer or antagonize the effects of this cytokine. This mechanism is important in regulating inflammatory responses and protecting tissues from excessive damage during immune activation. Measurement of these soluble receptors provides valuable clinical information about immune system status and disease progression across a range of pathological conditions including infections like HIV/AIDS, sepsis, autoimmune disorders such as rheumatoid arthritis or lupus erythematosus, cancers associated with chronic inflammation or dysregulated immunity. Therapeutically engineered versions—such as etanercept—exploit this natural regulatory mechanism by acting as decoy receptors to treat inflammatory diseases.[3][4][6]

Other names

Soluble TNF receptor type IsTNF-RIsoluble TNFR155 kDa TNF receptor (for type I)Soluble tumor necrosis factor receptor IIsTNF-RIIsoluble TNFR275 kDa TNF receptor (for type II)

Competitive binding to circulating TNFα to neutralize its activity and prevent interaction with cell surface receptors[4][6]