Prophylactic vaccine inhibits Eμ-myc–driven lymphoma in immunocompetent mice. WT and Jα18^KO C57BL/6 mice received 1 × 10⁵ live, unloaded, or α-GalCer–loaded Eμ-myc 299 tumor cells intravenously. (A) Representative flow cytometry plots showing tumor burden (gated B220⁺GFP⁺ cell population) at day 14 in blood in WT and Jα18^KO mice. (B) Data are mean ± SEM (n = 5); tumor burden in blood of WT and Jα18^KO mice challenged with unloaded or αGalCer-loaded tumor cells. Vaccinated WT mice were rechallenged at day 28 with 1 × 10⁵ parental Eμ-myc tumor cells, and tumor growth was compared with equivalent tumor inoculation into naive WT mice (right graph). (C) Percentage (left graph) and total cell count (right graph) of CD1d tetramer⁺ NKT cells in spleen of non–tumor-bearing or Eμ-myc tumor-bearing mice 7 days after inoculation. **P < .001 (unpaired t test). ***P < .0001 (unpaired t test). ns indicates not significant. Two independent experiments were performed.