Tumour-necrosis factor from the rabbit. IV. Purification and chemical characterization

Serum from rabbits with BCG/endotoxin-induced shock is growth inhibitory or cytotoxic to a range ot tumour cell lines. The active component, tumour-necrosis factor (TNF), has been purified 1000-fold by sequential salt precipitation, ion-exchange chromatography and gel-filtration. TNF had a mol. wt of 67,000 on gradient PAGE and 39,000 on Ultrogel AcA44 gel-filtration. The isoelectric point was pH 5.1-5.2. TNF was susceptible to the proteolytic enzyme pronase, but resistant to trypsin or papain. On isopycnic ultracentrifugation it had a buoyant density of 1.27, confirming that it is protein in nature, with little or no carbohydrate. This is also suggested by its failure to bind to a range of lectins.