CYTOTOXICITY AND ELECTRON MICROSCOPIC

Interleukin-2 (IL-2) - activated lymphocytes, known as lymphokine activated laller/ natural laller ce11s (LAKlNK) were generated by incubation of human mononuclear blood cells in medium containing different doses (100, 250, 500 and 1000 mimI) of IL-2 for 3-5 days. These cells were tested for their cytotoxic activity against K562 target cells in short term (4 h) and long term (18 h) SlCr-release assay at different effector/target (E/T) ratios (100/1, SOil, 25/1, 12.5/1 and 6.25/1) Non-IL-2 treated mononuclear cells were able to lysis the target cells up to 9.67 % and 27.6 % in short term and long term assays, respectively at EIT (100:1). Incubation of effector (LA KINK) cells with different doses of IL-2 showed increase in the cytotoxicity percentage at all EIT ratios. The maximum cytotoxic activity of LAKINK cells was detected at 50/1 (EIT) ratio in presence of 1000 IU/ml of IL-2 either at 4 h (70 %) or at 18 h (81.2 %) by using 51Cr-release assay. There were direct relationship. between the percentages of cytotoxicity induced by LAKINK cells and the concentrations of ll_-2 as well as increased Err ratios. IL-2 is a potent inducer of LAK activity against K562 tumor celJ line. The ultrastructural results of this investigation allowed us to study the most important moments of interaction between LAKINK cells and K562 target cells in vitro. Effector (LAKlNK) cells undergo several ultrastructural changes, they started to develop border irregularity and protrusions that came in direct contact with target cells and established various degrees of adh..esion up to the development of desmosomes