A human inhibitor of tumor necrosis factor alpha.

Urine of some febrile patients exhibits a TNF-alpha inhibitory activity (TNF-alpha INH), sensitive to heat and trypsin, with an apparent mol wt of 40-60 X 10(3) and a pI range of 5.5-6.1. As for the Il-1 INH, the TNF INH activity involves a competitive mechanism of action suggesting the existence of a family of negative feedback-regulating molecules interfering with cytokines actions.