悪性脳腫瘍免疫療法におけるimmune RNAの役割

THE ROLE OF IMMUNE RNA IN THE IMMUNOTHERAPY OF MALIGNANT BRAIN TUMOR

　抄録　現在，悪性脳腫瘍に対する免疫療法としてBCG,Picibanil等を用いた非特異的免疫療法が主に行われている。一方，腫瘍免疫受動伝達に重要な役割を果すリンパ球を用いた特異的免疫療法も試みられたが，この方法は組織適合性の相違，blocking factor等の問題を含んでいる。これらの問題点を解決するために，リンパ球より抽出したchemicalmediaterの効果が注目されているが，我々はC₆ gliorna cellで感作したラットの脾臓よりimmuneRNA （IRNA）を抽出し，このIRNAで処理した正常リンパ球の抗腫瘍性をin vivo,in vitro実験において観察した。（Ⅰ） In vitro実験：（1） IRNA処理リンパ球は有意なcytoto—xicityを示し，この効果はIRNAをRNaseで前処理すると消失した。（2） IRNAの抗腫瘍効果は腫瘍特異的であつた。（3） Syngeneic RNAのみならずxenogeneic RNAも有効であつた。更にIRNAが抗腫瘍性を伝達する際の至適条件について検討すると共に，sucrose density gradient centrifugation,oligo（dT） cellunose affnity chromatographyを用いてIRNAの精製を試みた。（II） ln vivo実験；IRNA処理リンパ球を脳腫瘍ラットに静注し，有意な延命効果をみた。以上IRNAはin vivo,in vitro実験において有効であることが示されたが，今後臨床的に用いていく上での問題点について検討した。

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 com-pensate for this disadvantage, specific immunothera-py 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 experi-ments. In in vitro experiment, following results were obtained.

(1) Normal lymphocytes incubated with im-mune RNA revealed a significant cytotoxicity andthis 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 xeno-geneic RNA were effective. In addition to these results, we decided the optimal condition in which immune RNA transferred the cell mediated cytoto-xicity to normal lymphocytes.

Next, we tried the purification of immune RNA by way of sucrose density gradient centrifugation method and oligo (dT) cellulose affinity chromato-graphy 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 in-travenously 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 im-mune 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 character-istics will be necessary.