Partial purification of a serum factor that causes necrosis of tumors

Tumor necrosis can be induced in transplanted mouse methylcholanthrene-induced sarcoma by a tumor necrosis factor in the serum of mice infected with bacillus Calmette-Guérin and given bacterial endotoxin. Sera from normal mice, endotoxin-treated mice, and mice infected with bacillus Calmette-Guérin do not contain this factor. A 20- to 30-fold purification of the serum factor has been achieved by (NH4)2SO4 fractionation, Sephadex G-100 and G-200 gel filtration, and preparative polyacrylamide electrophoresis. Tumor necrosis factor is not bacterial endotoxin. It migrates with alpha-globulins, is made up of at least four subunits, and has a molecular weight of about 150,000. The active factor is a glycoprotein that contains sialic acid and galactosamine.