A new sensitive and rapid automated fluorometric assay for detection of natural killer activity using carboxyfluorescein diacetate.

An automated fluorometric assay using carboxyfluorescein diacetate (CFDA) has been applied for the sensitive and rapid detection of natural killer (NK) activity. The lysis of target cells by NK cells was quantified by measuring the amount of CFDA released into the supernatant of culture wells with the aid of an automated microfluorometer. Both sensitivity and specificity of the presented method were higher than the 51Cr release assay. Moreover, the detection of human NK activity against K562 target cells required only 2 hrs, compared to 4 hrs in the standard 51Cr release assay.