Differentiation in mouse leukemia cells mediated by an immune interferon preparation

Antiviral and cell-differentiating (CD) activities of immune interferon (IFN-gamma) preparation were investigated. Male STD-ddY mice were sensitized with BCG. Three weeks later, they were challenged with BCG or purified protein derivative (PPD), and exsanguinated at intervals. The sera were assayed for antiviral and CD activities. The CD activity appeared and reached the maximum earlier than the antiviral activity. The CD activity was thermostable, whereas the antiviral activity was thermolabile. By dialysis at pH 2 for 24 h, the CD activity was reduced to 15%, while the antiviral titer was completely lost. Lipopolysaccharide (LPS) given 24 h before the challenge has markedly suppressed the appearance of antiviral activity following the challenge, but did not so much affect the CD activity. The challenge with PPD stimulated greater antiviral activity and poorer CD activity than the challenge with BCG did. These findings suggest that IFN-gamma preparations contain a CD factor(s) besides IFN.