An enzymatic assay for the detection of natural cytotoxicity

The pronase-enhanced release of 14C-labeled DNA was used to assay cytotoxicity of murine natural killer cells. YAC-1 lymphoma cells were labeled with [14C]thymidine and incubated with increasing numbers of spleen cells from nude mice. At harvest, nuclease-free pronase was used to digest damaged target cells. Increases in cytotoxicity of 5--39% were obtained using optimal conditions. The reaction could be successfully inhibited with unlabeled YAC-1 cells. The degree of cytotoxicity was similar to that detected by 51Cr release, but a longer period of incubation was required.