Fig. 3.

In vitro killing of cancer cells by purified leukocyte subsets from SR/CR mice. Individually purified leukocyte subsets from WT and SR/CR mice (described in Materials and Methods) were examined for their ability to kill S180 cells in a standard in vitro killing assay. The effector cells were incubated with S180 cells at a 10:1 ratio at 39°C for 24 h. Live S180 cells were identified by size, morphology, and fluorescence, and viability was determined by trypan blue exclusion. S, splenocytes; T, thioglycollate-induced peritoneal MΦ; M, MΦ; N/A, no leukocytes added. As a control, mixed populations of SR/CR leukocytes were incubated as described above with CHO or NIH 3T3 mouse fibroblast cells to determine whether S180 killing was specific to cancer cells or general to cultured cell lines.