Tumor Necrosis Factor (TNF) Binding Protein is isolated and substantially purified. It has the ability to inhibit the cytotoxic effect of TNF and/or to maintain its prolonged beneficial effects.TNF Binding Protein II and salts, functional derivatives, precursors and active fractions thereof can be used to antagonize the deleterious effects of TNP and to prolong its beneficial effectsPolyclonal and monoclonal antibodies to the TNF Binding Protein II are produced. They be used as pharmaceutical agents and in diagnostic assays.