In vivo and in vitro effect of adoptive immunotherapy of experimental murine brain tumors using lymphokine-activated killer cells

Abstract

Adoptive immunotherapy for the experimental murine brain tumor was investigated by using lymphokine-activated killer (LAK) cells both in vitro and in vivo. Supernatants of 48-h culture medium of spleen cells from Wistar rats in the presence of concanavalin A were used as interleukin 2 (IL-2). LAK cells were generated by cocultivation of spleen cells from Fischer rats with IL-2 with the peak reactivity on Day 2 or 3 of culture. Lytic activity was observed against not only syngenic tumor cells but also allogenic and xenogenic tumor cells, while no lytic activity was observed against normal brain cells. The cell depletion test, dye exclusion test, and immunofluorescence method using monoclonal antibodies revealed that LAK cells partially belonged to the population of the activated T-cell group, but the precursor cells did not react with any monoclonal antibodies used. On the basis of these results in vivo study was performed. LAK cells and immune spleen cells were adoptively transferred to the rats i.v. or intratumorally (i.t.) on the seventh day after the inoculation of T9, a gliosarcoma induced by methylcholanthrene from Fischer rats, into the right basal ganglia. Then the survival rate and necrotic foci were compared between the groups treated with those cells and the control. The survival rate of the groups treated with LAK cells was significantly higher than that of the control (administered i.v.; P less than 0.01, administered i.t.; P less than 0.05). But the treatment with immune spleen cells was not effective. The incidence and area of necrotic foci in the tumors treated with LAK cells were greater than those of the others. Microautoradiography was also performed using [3H]thymidine-labeled LAK cells, which were administered i.v. to the models on the 14th day after the inoculation of T9. It was revealed that LAK cells accumulated in the lung shortly after the administration and then in the liver and spleen, especially in the white pulp. IL-2 inhibitor activity of the sera from the tumor-bearing rats was greater than that of normal rats (P less than 0.001), but it was depressed markedly by cyclophosphamide (P less than 0.01). The adoptive transfer of LAK cells may be one of the effective treatments of malignant brain tumor. The nature of IL-2 inhibitors is necessary to be clarified for more effective immunotherapy.