Infusion of tumor necrosis factor (TNF) causes an increase in circulating TNF-binding protein in humans

Serum samples from cancer patients receiving intravenous infusions of recombinant tumor necrosis factor (rTNF) and recombinant interferon-gamma (rIFN-gamma) were analyzed for TNF and the TNF-binding protein (TNF-BP). TNF-BP is a soluble fragment of the transmembrane TNF receptor with antagonistic effects to TNF and is released by proteolytic cleavage of the receptor. During a 60-min infusion of rTNF, peak serum levels of rTNF were observed after 30 to 60 min and a transient increase of circulating TNF-BP was observed with peak levels between 30 and 120 min. Injection of IFN-gamma alone did not affect the levels of TNF and TNF-BP. Thus administration of rTNF leads to release into the circulation of TNF-BP, which may modulate both systemic and local effects of TNF and influence its therapeutic efficacy.