Selective degradation of tumor necrosis factor in sensitive cells, and production of membrane-active substance

The mode of action of tumor necrosis factor (TNF) was studied. On treatment of TNF-sensitive L929 cells with radioiodinated TNF, the TNF molecule was found to be internalized into the cells and extensively degraded. On treatment of TNF-insensitive embryonic fibroblast cells with TNF, less TNF was internalized and it was not degraded appreciably. The L929 cells excreted the degradation products of TNF into the culture medium, and this medium showed activity for degradation of liposomes composed of phosphatidylserine and phosphatidylcholine. The sensitive cells may contain some specific proteinase that cleaves TNF molecules.