Stage of tumor outcome determines NK activity in the spleen.

Ex vivo NK activity of spleen cells was evaluated, 3 weeks (Ai-Aiii) and 6 weeks (B) after BW-Sp3 tumor inoculation, by performing 18-hour¹¹¹In-release assays, using YAC-1 cells as the target population. (A) Spleen cells were isolated from naive mice (Ai), mice with regressing tumors (Aii), or mice with progressing tumors (Aiii) and were included as such (▪), or on complement mediated lysis of NK cells (treated with anti-DX5 and anti-ASGM-1, ♦), or CTLs (treated with anti-CD8, ○) in in vitro cytotoxicity experiments. (B) Splenic effectors from naive mice (+), mice with regressed tumors (▪), or mice with progressing tumors (♦) were harvested 6 weeks after tumor inoculation; viable cells were isolated on Ficoll and immediately included in a cytotoxicity experiment. Results are represented as means with SEM. One experiment representative of 3 (3 weeks after tumor inoculation) or of 5 (6 weeks after tumor inoculation) is shown.