Characterization of L1210 murine leukemia and P815 murine mastcytoma cells. (A) L1210 and P815 cells were cultured in the presence of recombinant TNF- for 24 hours and then cell viability was analyzed using the alamar Blue method. Both L1210 and P815 were resistant to TNF-, whereas L929 was susceptible to TNF-. (B)⁵¹Cr-labeled L1210 or P815 cells were cocultured with murine FasL transfectant (mFasL/L5178Y) cells at the indicated E/T ratios for 6 hours and then cytotoxicity was measured by⁵¹Cr-release assay. (C) Proliferative response of spleen cells obtained from wild-type, gld, or PKO B6 mice against allogeneic L1210 or P815 cells. Spleen cells (2 × 10⁵) were cultured with irradiated L1210 or P815 cells (2 × 10⁴) for 5 days and pulsed with ³H-TdR during the last 16 hours. Spleen cells were prepared from one mouse of each strain and were used immediately after preparation. Data are represented as the mean ± SD of triplicated samples. Spleen cells obtained from each mouse responded equally to L1210 or P815 cells. (D) Killing of L1210 cells by CTL derived from wild-type, gld, and PKO B6 mice. Spleen cells were collected after 5 days of coculture with irradiated L1210 cells as described in (B) and restimulated with irradiated L1210 cells in the presence of 10 U/mL IL-2 for 5 days. CTL activity was tested against ⁵¹Cr-labeled L1210 or P815 target cells at the indicated E/T ratios. Although killing activity of CTL derived from gld mice was only slightly diminished as compared with that from wild-type mice, PKO-derived CTL exhibited no significant cytotoxicity against L1210 cells. Data are represented as the mean ± SD of triplicated samples. A representative of three experiments is shown.