Augmentation of in vitro cytolytic activity of LAK cells with heated ATL-derived cell lines

Three adult T-cell leukemia/lymphoma-derived cell lines, MT-2, MJ, and HUT102, were investigated to determine how they responded to hyperthermia, lymphokine-activated killer (LAK) cells, or a combination of both in vitro. All three cell lines showed a similar sensitivity to LAK cells, but revealed varying degrees of sensitivity to hyperthermia (MT-2 < MJ < HUT102) by 51Cr release assay. Hyperthermia did not cause immediate cell death as determined by the trypan blue exclusion test, but did cause substantial decreases in the numbers of heated cells within 2 days. The density of the cells began to increase thereafter, which was consistent with the results of the experiments labeling the cells with 3H-TdR after hyperthermia. When the cells were heated at 39-43 degrees C for 1-3 hr and then interacted with various LAK cell/ATL cell (E/T) ratios at 37 degrees C for 4 hr, total cytolysis of the cells increased in a synergistic and/or additive manner over that of the cells without hyperthermia. Prolonged incubation of the cells at high temperature did not necessarily cause a large increase in the interaction of LAK cells after hyperthermia. This augmentation of cytolysis by LAK cells after hyperthermia was not seen in normal peripheral lymphocytes. These results suggest that the combination therapy of hyperthermia and LAK cells may be more specific, useful, and effective for treating malignant lymphoma.