Blockade of NKG2 enhances activation of naive and α-GalCer–primed iNKT cells by α-GalCer in vivo. (A) Mice were primed with α-GalCer on day 0 and then boosted with α-GalCer on the indicated day. Anti-NKG2 mAb (•) or control Ig (○) was administered 2 days before the boost. Serum samples were obtained 5 hours after the boost. The mice indicated on day 0 were treated once with α-GalCer injection on day 0. (B) Cytotoxic activity of liver and spleen MNCs was tested against NK-sensitive YAC-1 cells and NK-resistant P815 cells 24 hours after the last α-GalCer injection. Mice were intraperitoneally injected with α-GalCer on day 0 (squares) or days –3 and 0 (circles), or injected with vehicle on days –3 and 0 (triangles), and intraperitoneally administered with anti-NKG2 mAb (closed symbols) or control Ig (open symbols) on day –2. Data are represented as the mean ± SD of triplicate samples. Similar results were obtained from 3 independent experiments. (C) Antimetastatic effect. Mice were intraperitoneally injected with α-GalCer on day 0 or days –3 and 0, and then intravenously inoculated with 3 × 105 B16 melanoma cells 2 hours later. Anti-NKG2 mAb or control Ig was intraperitoneally administered on day –2. On day 14, the number of tumor colonies in the lungs was counted under a dissecting microscope. Data are represented as the mean ± SD of 5 to 8 mice in each group. Similar results were obtained from 3 independent experiments.
