TNF inhibitor with a low molecular weight found in the human sera.

We found a TNF inhibitory factor with a molecular weight of 5 to 10 kDa in the human sera. The activity was detected by inhibiting the activity of serum to TNF-induced cytotoxicity against target cells. It was found in sera of all the healthy donors tested without any febrile diseases. Moreover, our results demonstrated that TNF inhibitory factor decreases in the semum of patients on regular hemodialysis treatment and in the serum of diabetes mellitus patients. The activity found in human sera was eluted from DEAE-cellulose column (Mono Q) at 0.25 and 0.45 M NaCl, and was labile to incubation for 60 min at 56 degrees C and susceptible to treatment with trypsin, which destroyed 60% of its biological activity. TNF inhibitory factor may act as a regulator of the biological activity of TNF and could have beneficial effects in certain inflammatory conditions, and therefore, could be useful in clinical application.