TNFRI belongs to the TNFR superfamily of transmembrane proteins, and is expressed in most cell types. Binding of either TNF-alpha or TNF-beta to TNFRI initiates a signal transduction pathway that results in the activation of the transduction factor NF-kappaB, whose target genes are involved in the regulation of inflammatory responses, and, in certain cells induce apoptosis. Soluble TNF Receptor I (sTNFRI) is capable of inhibiting TNF-alpha and TNF-beta activities by acting as a decoy receptor that serves as a sink for the TNF ligands. The human TNFRI gene encodes for a 455 amino acid type I transmembrane protein, which contains a 21 amino acid signal sequence, a 190 amino acid extracellular domain, a 23 amino acid transmembrane domain, and a 221 amino acid cytoplasmic domain. Recombinant Human sTNF Receptor Type I is an 18.3 kDa protein (162 amino acid residues) comprising the cysteine-rich, ligand-binding portion of the extracellular domain of the TNFRI protein.