Evidence for the presence of an antitumor factor in serum of normal animals.

We have previously reported finding a factor with antitumor activity (TNF, tumor necrosis factor) in extracts of serum from normal mice. The possibility that TNF exists in the blood of normal animals of other species was explored. Horse, mouse, dog, human, sheep, calf, rat and shark serums were fractionated with (NH4)2SO4 and filtered through S-200 sephacryl gel. Proteins of molecular weight 90,000 to 180,000 were pooled, concentrated and dialyzed. TNF, determined by L-cell assay in vitro and Meth A assay in vivo found in fractions from mouse, dog and human serum. Agarose electrophoresis of the TNF from mouse and human serum indicated the principle components were alpha 1-alpha 2 globulins. Preparative PAGE indicated that mouse TNF migrated slowly and was made up of at least 4 components while human TNF was a faster moving, monomeric protein.