Vaccination with irradiated CD1d^hi-NIH3T3/Gal-trp2 induces protection from melanoma. mRNA from the melanocyte differentiation antigen, trp2, was transduced into NIH3T3 cells. Trp2 expression on B16 cells and trp2 mRNA–transduced NIH3T3 cells was evaluated by (A) RT-PCR and (B) real-time PCR. (C) WT mice were immunized with 5 × 10⁵ CD1d^hi-NIH3T3/Gal, CD1d^hi-NIH3T3-trp2, and CD1d^hi-NIH3T3/Gal-trp2 intravenously. At 2 weeks later, the mice were challenged subcutaneously with 5 × 10⁴ B16 or 2 × 10⁵ EL4 cells. Tumor size in each group was measured at the indicated time points (n = 6-8 per group). Similar results were obtained in 2 independent experiments. (D) Antitumor responses to established tumor were assessed. C57BL/6 mice were injected 5 × 10⁴B16 subcutaneously (top panel). The mice were given 5 × 10⁵ CD1d^hi-NIH3T3/Gal-trp2 intravenously at 5 days and again at 12 days. Tumor size was evaluated at the indicated time points (n = 6-10 per group). ↓ indicates the treatment with CD1d^hi-NIH3T3/Gal-trp2.