Purification of natural killer cell cytotoxic granules for assaying target cell apoptosis

Abstract

We compared two methods originally devised to purify cytoplasmic granules from granulocytes for their capacity to produce cytotoxic granules from natural killer cell lines, suitable for use in target cell apoptosis assays. Both methods utilised nitrogen cavitation to efficiently lyse cells, followed by density gradient fractionation on Percoll to separate the granules from other organelles and granule debris. The first method, originally described by Millard and colleagues, employed DNase I to reduce the viscosity of the initial cell lysate, but the resulting granule fractions were found to contain residual nuclease activity that made them unsuitable for use in apoptosis assays that measure ..