Macrophagemediated cytolysis release of radioisotopes

The morphological assay is quite laborious and does nol distinguish between cytostasis and cytolysis. As a result, other methods based on the use of radioisotopes were developed to provide a more convenient tool to assess macro-phage-mediated tumour cell killing. These techniques employ the quantitative release of intracellular radioisotopes as a measure of tumour cell destruction. Three different and commonly used isotopic release assays that measure cytolysis arc described in this section.

2,2.1 51Cr release assay

Protocol 2 describes one method for the 5lCr release assay, a convenient and reliable method that employs a cytoplasmic label, the gamma emitter 51Cr. This assay can be used to quantify lysis of susceptible leukaemia, lymphoma, or mastocytoma cells by mouse peritoneal macrophages and murine macrophage cell lines (8-12). However, the relatively high 'spontaneous release' by labelled target cells cultured alone or with resting macrophages (1 -2% per hour) restricts the usefulness of 5,Cr to relatively short-term assays (18-24 hours). In addition, its use is limited by the relatively low number of susceptible targets that incorporate the label.

Protocol 2

Measurement of macrophage-mediated cytolysis by the 51Cr release assay

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