[The role of immune RNA in the immunotherapy of malignant brain tumor (author's transl)].

At present, nonspecific immunotherapy using BCG or Picibanil is popular as an immunotherapy for malignant brain tumor. On the other hand, specific immunotherapy using lymphocytes which play an important role in the passive transmission of tumor immunity is also performed. But this therapy has some disadvantage such as the problem of blocking factor or histocompatibility. To compensate for this disadvantage, specific immunotherapy using the chemical mediater, immune RNA, extracted from immunized lymphocytes has started. We extracted immune RNA from the spleen of immunized rat using phenol and SDS, and observed the effect of normal lymphocytes preincubated with immune RNA in vitro and in vivo experiments. In in vitro experiment, following results were obtained. (1) Normal lymphocytes incubated with immune RNA revealed a significant cytotoxicity and this effect was disappeared by the pretreatment of immune RNA with RNase. (2) Cytotoxic effect of immune RNA seemed to be a tumor specific response. (3) Not only syngeneic RNA, but also xenogeneic RNA were effective. In addition to these results, we decided the optimal condition in which immune RNA transferred the cell mediated cytotoxicity to normal lymphocytes. Next, we tried the purification of immune RNA by way of sucrose density gradient centrifugation method and oligo (dT) cellulose affinity chromatography method. Active fraction of immune RNA was contained in 8-16 S fraction and in poly (A) containing fraction. As in vivo experiment, we injected immune RNA incubated lymphocytes intravenously to brain tumor-bearing rats and observed for death daily. In this experiments, significant prolongation of mean survival time was recognized in the group treated with immune RNA. We now consider the clinical application of immune RNA for malignant brain tumor by the following method: immune RNA is obtained from the lymphocytes of sheep which has immunized with patient's tumor cells. And then patient's own lymphocytes strengthened by incubation with immune RNA is injected intratumorally by way of Ommaya's reservoir. To do this therapy safely and effectively, further purification of immune RNA and solution of its physiochemical characteristics will be necessary.