Human interferon and cell growth inhibition. II. Biological and physico-chemical properties of the growth inhibitory component.

Human leukocyte interferon (IF) inhibits the growth rate of homologous cells in culture. The growth inhibitory component, formerly separated from the antiviral component of human leukocyte IF by adsorption chromatography on albumin-agarose, is investigated. The properties of the component are compared with the accepted characteristics of IF. The growth inhibition is caused by a small molecule, unstable to pH 2 treatment with HCl, but stable to trichloro-acetic acid (TCA) and to proteolytic enzymes. The siolated growth inhibitor seems to be a dimer of molecular weight (mol wt.) approximately 2300. It is activated by heat treatment and lacks species specificity. The discrepancies in the properties of the growth inhibitor before and after separation from IF are discussed.