BM cytotoxicity after prolonged exposure to IL-2. BM mononuclear cells were isolated and set up in culture with IL-2 (500 U/mL) for 7 days. After this time, the cells were washed and their cytotoxicity against Daudi and YAC-1 cells measured in cytotoxicity assays. Individual results are shown. A standard E:T of 25:1 was used. The average spons/max ratios were 11.1% and 7.0% for Daudi and YAC-1 cells, respectively.