CYTOTOXICITY AND ELECTRON MICROSCOPIC

Abstract

Interleukin-2 (IL-2) - activated lymphocytes, known as lymphokine activated killerl natural killer cells (LAKfNK) were generated by incubation of human mononuclear blood cells in medium containing different doses (l00, 250, 500 and 1000 IV/mI) of IL-2 for 3-5 days. These cells were tested for their cytotoxic activity against KS62 target cells in short term (4 h) and long term (18 h) S1Cr-release assay at different effector/target (EIT) ratios (10011, SOIl, 2511, 12.5/1 and 6.2511) 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, respe.ctively at FjT (100: 1). Incubation of effector (LAKlNK) 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 SOil (E/T) ratio in presence of 1000 IV/ml of IL-2 either at 4 h (70 %) or at 1'8 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 IL-2 as well as increased Err ratios. IL-2 is a potent inducer of LAK activity against K562 tumor ceil line. The ultrastructural results of this investigation allowed us to study the most important moments of interaction between LAKINK cens and K562 target cens 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 adhesion up to the development of desmosomes