51Cr-release assay adapted to a 96-well format sample reading.

The application of the Matrix 96, a direct beta counter, to monitor cell-mediated lympholysis assays (CML) was investigated. Until now, the gamma rays emitted from 51Cr, released in the supernatant of the sample following lysis of targets by effector cells, were read in gamma counters using individual tubes for each sample. The Matrix 96 has been designed to count 96 wells simultaneously for assays performed in 96-well microplates. Aliquots of supernatants were spotted on a 96-well disposable metal spotting plate and dried prior to reading in the Matrix 96. A tight correlation was observed between the counts obtained in the Matrix 96 and a gamma counter, which indicates that the detection of electron capture beta particles emitted from 51Cr was as accurate as reading gamma rays from the same isotope. Both methods confirmed the minimal level of cytotoxicity mediated by unstimulated lymphocytes and the high levels of nonspecific cytolytic activity mediated by lymphokine-activated killer (LAK) cells against several tumor cell lines.