Flow cytometry evaluation of cell-mediated cytotoxicity

A novel flow cytometry method for the evaluation of cell-mediated cytotoxicity is described. This method uses flow cytometry analysis to distinguish target cells from effector cells by differences in volume and light scatter characteristics. Non-viable target cells, following their interaction with effector cells, are determined via propidium iodide (PI) dye exclusion and then expressed as a percentage of the total target cell population. This assay is suitable both for analysis of systems which allow recycling of cytotoxic effector cells (total cell cytotoxicity assays, TCCA), and of systems in which recycling does not occur (single cell cytotoxicity assays, SCCA). Natural killer (NK) cell-mediated cytotoxicity evaluated by flow cytometry is significantly correlated with the standard ⁵¹Cr release assay. Flow cytometry can also be used to evaluate the competitive inhibition that certain cell types exert on the cell-mediated killing of NK-sensitive targets. A prerequisite for this assay is that competitor cells and target cells are distinguishable through their volume and light scatter characteristics. Advantages and pitfalls of the flow cytometry method are discussed, in comparison with the ⁵¹Cr-release assay.