A second tumor necrosis factor receptor gene product can shed a naturally occurring tumor necrosis factor inhibitor

An inhibitor of tumor necrosis factor (TNF) has been isolated from the human histiocytic lymphoma cell line U-937 that is capable of inhibiting both TNF-alpha and TNF-beta. Protein sequencing has verified that it is distinct from a previously described TNF inhibitor that is a soluble fragment of a TNF receptor molecule (TNFrI). The cDNA sequence of this second TNF inhibitor clone suggests that it is also a soluble fragment of a TNF receptor. Expression of this cDNA sequence in COS-7 cells verified that it encodes a receptor for TNF-alpha (TNFrII) that can give rise to a soluble inhibitor of TNF-alpha, presumably through proteolytic cleavage. The extracellular domain of TNFrII has significant homology with that of TNFrI and these two receptors share a striking conservation of cysteine residue alignment with the extracellular domain of the nerve growth factor receptor. These three receptor molecules are therefore members of a family of polypeptide hormone receptors.