Defective antitumor surveillance by Pten-deficient Vα14iNKT cells. (A) Scheme describing the experimental protocol used to evaluate antitumor surveillance by NKT cells in vivo. Vα14iNKT cells were purified from mice of the indicated genotypes and adoptively transferred into Jα18^−/− mice that had been inoculated with B16F10 melanoma cells. The mice were then injected with αGalCer at 0, 4, and 8 days after NKT cell transfer. After 14 days, numbers of focal lung metastases were counted. (B-C, left panels) Increased lung metastasis. Quadrant scheme in the upper corners shows the labeling of the cell images. “None” indicates controls in which no cells were transferred. Representative images of lung metastases 2 weeks after the transfer of Pten^flox/flox or LckCrePten^flox/flox Vα14iNKT cells (B) or after the transfer of Pten^+/+ or Pten^+/− Vα14iNKT cells (C) are shown. (B-C, right panels) Relative numbers of the lung metastases identified in the left panels. Results shown are mean ± SEM of 18 mice that received no cells and 6 mice each that received Vα14iNKT cells. **P < .01.