Induction of cytotoxic activity and antimetastatic effect by priming and boosting with α-GalCer and OCH. (A) Cytotoxic activity of liver and spleen MNCs was tested against NK-cell–sensitive YAC-1 cells or NK-cell–resistant P815 cells 24 hours after α-GalCer injection into mice primed 2.5 days earlier with vehicle (▵), αGalCer (□), or OCH (○). Control mice were primed and boosted with vehicle (▿). Proportion of iNKT cells (%) in respective MNC populations at the time of boosting injection is indicated in Table 1. Data are represented as the mean ± SD of triplicate samples. Similar results were obtained from 3 independent experiments. E/T indicates effector-to-target ratio. (B) Antimetastatic effect. Mice were primed and boosted with α-GalCer, OCH, or vehicle on days –3 and 0 as indicated. Then, the indicated number of B16 melanoma cells were intravenously inoculated into the mice 2 hours after the boost. On day 14, the number of tumor metastatic colonies in the lungs was counted. Data are represented as the mean ± SD of 5 mice in each group. Similar results were obtained from 3 independent experiments.