Human lymphotoxin: purification and some properties.

Lymphotoxin is secreted by human lymphocytes stimulated with phytohemagglutinin in vitro. Combinations of DEAE-cellulose and Sephadex chromatography, acrylamide gel electrophoresis, and isoelectric focusing were used to purify lymphotoxin 2000- to 4000-fold; 15-25% of the activity has been recovered. Lymphotoxin appears to be a weakly charged molecule(s) of molecular weight about 90,000-100,000 that migrates in Pevikon block electrophoresis as a beta- or alpha2 globulin. It is a discrete molecule(s), because it is completely separable from medium serum proteins and carrier and phytohemagglutinin proteins. Isoelectric-focusing studies indicate that there may be a limited heterogeneity among lymphotoxin molecules.