Brief Communication: Immune Cytolysis of Rat Tumor Cells Mediated by Syngeneic “Immune” RNA2

Abstract

Normal, nonimmune Fischer 344/N rat Iymphocytes were converted to effector cells, specifically cytotoxic to MC3-R tumor cells, by incubation in vitro with syngeneic “immune” RNA extracted either from the spleens of s)fngeneic Fischer 344/N rats bearing growing MC3-R tumor transplants or from the spleens of rats hyperimmunized with the MC3-R tumor. The degree of cytotoxicity obtained by this method was comparable in magnitude to the cytotoxicity of spleen cells from hyperimmunized rats. Spleen cells incubated with RNA from Fischer 344/N rats bearing a different tumor failed to lyse MC3-R tumor cells. These immune responses were abrogated when immune RNA was treated with RNAse before incubation with spleen cells, but treatment with DNAse or pronase d id not affect the activity of the immune RNA preparations. Concentrations of immune RNA as low as 100 µg/ml were effective in mediating these immune responses.