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