RAPID FLOW CYTOMETRIC ASSAY FOR THE ASSESSMENT OF NATURAL-KILLER-CELLACTIVITY

A new assay using flow cytometry has been established to assess natura l killer (NK) lytic activity with common bench top instrumentation. Th is assay uses a cyanine membrane dye to stain live K562 target cells a nd an iodide nuclear dye to evaluate dead cells, and provides a method of reliably separating target and effector cell populations. Effector cells remain unstained (fluorescent negative) throughout the procedur e. The damaged pre-labeled targets appear doubly stained as their memb ranes become permeable to the nuclear stain during incubation. Percent cytotoxicity of various effector:target cell ratios is discerned usin g flow cytometric analysis after a 2 h incubation in this new assay, a s compared to 4 h with the Cr-51-release 'gold standard' assay for cel l-mediated cytotoxicity. Comparisons of normal individuals tested in p arallel with the fluorescent dyes and the Cr-51-release assay have sho wn direct correlations. This new two-color flow cytometric technique h as proven to be uncomplicated and reproducible when used in the clinic al setting.