Rat interferons. Homologous and heterologus rat serum activity.

Serum proteins from normal rat serum and induced with Sindbis virus were separated on Sephadex G-100. Interferon activity was studied in a system of homologous REC and heterologous LG cells. Proteins of normal serum as well as induced serum emerged in two peaks separated by a deep saddle. Four hours after induction, the serum gave two peaks with similar interferon activity in both cell systems. After 8-hour induction, two interferons were also obtained, but activity in the heterologous system was much lower than in the homologous system. Electrophoresis in polyacrylamide gel and on paper showed that interferon activity is connected mainly with the alpha1-globulin fraction.