[Induction of LAK cells from rat splenocytes and an anti-tumor effect of the LAK cells on the 9L-gliomas].

The author observed a fact that the incubated splenocytes of the Fischer strain rats with recombinant human interleukin-2 (rIL-2) developed lytic activity to syngeneic natural killer-resistant 9L-glioma cells by a 4-h Cr release assay. The induction of their lymphokine-activated killer (LAK) cell was as follows. 1) When 5 •~ 106/ml splenocytes were cultured with various concentrations of rIL-2 (50, 125, 250, 500, 1,000U/ml) for 4 days, the numbers of harvested viable cells increased in responsed to the concentration. The peak was obtained at 500U/ml of rIL-2. And the significant killer activity to 9L-glioma cells was observed at 35-45% (Effector/Target ratio=100/1) in each concentration of rIL-2. 2) When 5•~106/ml splenocytes were cultured for 1 to 7 days with 250U/ml rIL-2, the discernible lytic activity to 9L-glioma cells was observed on the 1st day culture and with the peak activity on the 4th day. Moreover, LAK cells prepared from a brain tumor rat showed lytic effect against for the 9L-glioma cells similar to LAK cells from a normal rat. According to Winn's assay, the growth of tumor was significantly inhibited on the subcutaneous inoculation of 5 •~ 104 9L-glioma cells mixed with 5•~10•¬6 LAK cells.