An [35S]methionine cytotoxicity assay requiring small numbers of effector and target cells

This communication describes an assay to detect polyclonal cytotoxic activity of small numbers of effector cells. 200 tumor target cells, radiolabelled with 10,000-20,000 cpm [35S]methionine, are incubated with proportionately few effector lymphocytes in microtiter wells. The targets are sufficiently well labelled to permit detection of cytolysis caused by greater than or equal to 1000 cytotoxic cells, at effector:target ratios as low as 5:1. This method permits the rapid assay of limited numbers of effector cells, avoids lengthy culture of effector cells in order to acquire sufficient numbers, and is useful for limiting dilution analysis of cytotoxic T lymphocytes or their precursors.