Berish Y. Rubin

Human Tumor Necrosis Factor (LuKII): Recent Developments

TNF(LuKII) derived from the culture media of the LuKII B cell line has been purified to a specific activity of 1.5 × 107 units/mg of protein. Fractionation of the purified TNF(LuKII) by sodium dodecyl sulfate polyacrylamide gel electrophoresis reveals the presence of seven protein bands. Peptide mapping analyses and immunoblotting studies reveal that all seven protein bands are related. Treatment of purified TNF(LuKII) with the endoglycosidase Endo F results in a reduction of the molecular weights of all of the TNF(LuKII) species, demonstrating the presence of N-linked oligosaccharides on the TNF(LuKII) molecules. The removal of the N-linked sugars does not reduce the number of molecular weight species present. 125I-labelled TNF(LuKII) binds specifically to cell surface receptors. The TNF sensitive L(M) and HeLa cell lines appear to have 200 - 300 receptors for TNF(LuKII) per cell. While the inability of a cell to bind TNF(LuKII) appears to be indicative of that cells resistance to the cytotoxic effect of TNF(LuKII), the ability of a cell to bind TNF(LukII) does not necessarily indicate sensitivity to the cytotoxic effect.