A TETRAZOLIUM-BASED COLORIMETRIC MTT ASSAY TO QUANTITATE HUMAN MONOCYTE MEDIATED CYTOTOXICITY AGAINST LEUKEMIC-CELLS FROM CELL-LINES AND PATIENTS WITH ACUTE MYELOID-LEUKEMIA

The MTT-colorimetric monocyte mediated cytotoxicity assay, based upon the ability of living cells to reduce 3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyltetrazolium bromide (MTT) into formazan, was evaluated using leukemic cells from five representative human leukemic cell lines and from 28 patients with acute myeloid leukemia (AML), An excellent linea rity between absorbance and leukemic cell number was observed up to 5X 10(4) cells/well and 50 x 10(4) cells/well for all cell lines and pati ents samples tested, respectively, in a 96-wells microtiter culture sy stem. A huge variability in the susceptibility of leukemic cells to pu rified and IFN-gamma-activated human monocytes could be observed at ef fector-to-target cell (E:T) ratios of 1. The mean signal-to-noise rati o of the MTT assay for monocyte-leukemic cell mixtures from patients w as 2.69+/-0.39 at E:T 1. In conclusion, the MTT based monocyte mediate d cytotoxicity assay should be useful for studying the susceptibility of a variety of leukemic cells from cell lines and from patients with AML to monocytes in a rapid, sensitive and semi-automated manner.