[Analysis of the immunosuppressive mechanism in patients with malignant brain tumors].

Immunosuppressive mechanisms in patients with malignant brain tumors were studied with the use of a nylon wool column and monoclonal antibodies. Peripheral blood lymphocytes (P.B.L.) from the patients (82 malignant gliomas, 65 metastatic brain tumors) were tested for their ability to inhibit lymphocytoblastogenesis, and reacted with monoclonal anti Leu 1, 2a and 3a antibodies to identify the subsets of T lymphocytes. Depression of the lymphocytoblastogenesis was detected significantly by the patients' P.B.L. passed through the nylon-wool column, but not detected by that adhering to the column. This suppressor cell activity was shown to do its work over the barrier of major histocompatibility complex, and seemed to be associated with Con. A-induced suppressor cell activity. Especially, in the patients with malignant gliomas, the suppressor T cells seemed to be induced by tumor cells, and mediate the noted immunodepression. Furthermore, analysis of T cell subsets using monoclonal antibodies showed that the suppressor cell activity in the patients with malignant gliomas seemed to be closely correlated with Leu 2a+ cells, and the Leu 3a+/Leu 2a+ ratio decreased with tumor loads suggesting that the suppressor T cells are more dominant than the helper T cells. These immunological studies help to advance therapeutic protocols of the patients, because suppressor cells may be related to the escape mechanism of malignant brain tumors.